Outflow graft assistance apparatus for use with left ventricular assist devices and methods of using the same

Abstract

A system for implanting a graft includes a vascular clamp, a graft clamp, and a graft assistance apparatus. The vascular clamp includes a body portion and an occlusion portion. The occlusion portion may clamp a blood vessel to occlude a portion of the blood vessel. The graft clamp may clamp a piece of graft material. The graft assistance apparatus is secured to the vascular clamp and includes a securement segment and a clamping segment. The securement segment has an arm extending therefrom to secure the graft assistance apparatus to the body portion of the vascular clamp. The clamping segment defines a receiver with the graft clamp received in the receiver. The clamping segment is pivotally coupled to the securement segment such that the graft clamp is positioned at a graft angle.

Description

OUTFLOW GRAFT ASSISTANCE APPARATUS FOR USE WITH LEFT VENTRICULAR ASSIST DEVICES AND METHODS OF USING THE SAMEGovernment Support

[0001] This invention was made with government support under Award No. 2019259362 awarded by National Science Foundation (NSF) Graduate Research Fellowship Program. The government has certain rights in the invention.Cross-Reference to Related Applications

[0002] This application claims priority to, and benefit of, U.S. Provisional Patent Application Serial No. 63 / 678,885, filed August 2, 2024, the entire contents of which are hereby incorporated by reference.Background1. Technical Field

[0003] The present disclosure relates to surgical instruments and, more specifically, to outflow graft assistance apparatus for deployment of left ventricular assist devices (“LVAD”) and methods of using the same.2. Discussion of Related Art

[0004] Heart disease is the leading cause of death in the United States and globally. Heart failure specifically impacts more than 26 million patients across the world. Of these patients, an estimated 1.3 million to 2.6 million suffer from end-stage heart failure. Left ventricular assist devices (LVADs) have been used to help many heart failure patients. However, these patients suffer from increased risk of complications such as right ventricular failure, gastrointestinal bleeding, and stroke. While many of these occurrences may be caused by the design of the specific device used and the interaction of its effect on hemodynamics with the patients’ anatomy and natural blood flow, some evidence has been shown to support the theory that specific methods of surgical deployment of LVADs, specifically at the anastomosis site, may increase the risk of these negative outcomes.Summary

[0005] This disclosure relates generally to devices and methods for implantation LVADs in patients. More specifically, this disclosure relates to devices and method for attaching a graft to an ascending aorta of patient at a desired outflow graft angle during implantation of an LVAD.

[0006] In an aspect of the present disclosure, a system for implanting a graft includes a vascular clamp, a graft clamp, and a graft assistance apparatus. The vascular clamp includes a body portion and an occlusion portion extending from the body portion. The occlusion portion is configured to clamp a blood vessel to at least partially occlude a portion of the blood vessel. The body portion is disposed along a longitudinal body axis and the occlusion portion is disposed along an occlusion axis. The occlusion axis is offset from the longitudinal body axis in a range of 0 degrees to 90 degrees. The graft clamp is configured to clamp a piece of graft material therein. The graft clamp is disposed along a clamp axis. The graft assistance apparatus is secured to the vascular clamp. The graft assistance apparatus includes a securement segment and a clamping segment. The securement segment has an arm extending therefrom to secure the graft assistance apparatus to the body portion of the vascular clamp. The securement arm defines a passage that is disposed about a securement axis. The passage is secured about the body portion of the vascular clamp such that the longitudinal body axis is parallel with the securement axis. The clamping segment defines a receiver that is disposed about a receiver axis. The graft clamp is received in the receiver such that the clamp axis is parallel to the receiver axis. The clamping segment is pivotally coupled to the securement segment such that the graft clamp is positioned at a graft angle defined between the occlusion axis of the occlusion portion of the vascular clamp and the clamp axis of the graft clamp.

[0007] In aspects, the graft assistance apparatus includes a pivot break that selectively fixes a rotational position of the clamping segment with respect to the securement segment to position the graft at the clamp angle. The pivot break may include a clutch disposed on the securement segment and a prong disposed on the clamping segment. The clutch may define a plurality of notches. The prong may be selectively receivable in each notch of the plurality of notches to fix the rotational position of the graft clamp at the graft angle. The pivot break may include outflow angle indicators that visually indicate the graft angle when the prong is received in a respective notch. The clutch may have an arcuate profile.

[0008] In some aspects, the graft angle is in a range of 30 degrees to 90 degrees. The securement may extend from the securement segment at an offset angle from a first surface of the securement segment. The offset angle of the securement arm is such that the securement arm secures the securement segment to the body portion of the vascular clamp with the first surface parallel to the occlusion axis of the occlusion portion of the vascular clamp.

[0009] In certain embodiments, the vascular clamp is a partial occlusion vascular clamp. The graft clamp may be a bulldog vascular clamp. The graft clamp may be configured to fluidly seal an entirediameter of the piece of graft material clamped therein. The graft assistance apparatus may be sterilizable. The securement arm may form a snap fit to the body portion of the vascular clamp to secure the securement segment thereto. The securement arm may include a lock knob that locks the position of the graft assistance apparatus on the body portion of the vascular clamp. The graft angle may be calibrated to the correspond to an outflow graft angle of the piece of graft material when the piece of graft material is grafted to the blood vessel. Th graft assistance apparatus may be formed of a transparent or translucent material.

[0010] In another aspect of the present disclosure, a graft assistance apparatus for grafting a piece of graft material to a blood vessel includes a securement segment and a clamping segment. The securement segment includes a securement arm extending therefrom. The securement arm defines a securement axis. The securement arm is configured to secure the securement segment to a body portion of a vascular clamp having an occlusion portion extending therefrom that defines an occlusion axis. The clamping segment defines a receiver configured to receive a graft clamp therein. The receiver defines a receiver axis. The clamping segment is pivotally coupled to the securement segment and is configured to position the graft clamp at a graft angle defined between the receiver axis an and the occlusion axis when the graft clamp is received in the clamping segment and the securement segment is secured to the vascular clamp. The graft angle is calibrated to correspond to an outflow graft angle of the piece of graft material when the piece of graft material is grafted to the blood vessel.

[0011] In another aspect of the present disclosure, a surgical kit includes a vascular clamp, a graft clamp, and a graft assistance apparatus. The graft assistance apparatus is for grafting a piece of graft material to a blood vessel includes a securement segment and a clamping segment. The securement segment includes a securement arm extending therefrom. The securement arm defines a securement axis. The securement arm is configured to secure the securement segment to a body portion of a vascular clamp having an occlusion portion extending therefrom that defines an occlusion axis. The clamping segment defines a receiver configured to receive a graft clamp therein. The receiver defines a receiver axis. The clamping segment is pivotally coupled to the securement segment and is configured to position the graft clamp at a graft angle defined between the receiver axis an and the occlusion axis when the graft clamp is received in the clamping segment and the securement segment is secured to the vascular clamp. The graft angle is calibrated to correspond to an outflow graft angle of the piece of graft material when the piece of graft material is grafted to the blood vessel.

[0012] In another aspect of the present disclosure, a method of implanting a graft includes clamping a portion of a blood vessel of a patient with a vascular clamp to partially occlude blood flow throughthe blood vessel. The method also includes fixing a securement segment of a graft assistance apparatus to the vascular clamp. The method also includes clamping a piece of graft material in a graft clamp. The method also includes fixing the graft clamp to a clamping segment the graft assistance apparatus. The method also includes pivoting the clamping segment relative to the securement segment to a graft angle such that the piece of graft material is positioned at an outflow graft angle relative to the partially occluded portion of the blood vessel.

[0013] In aspects, clamping the portion of the blood vessel occurs before fixing the securement segment to the graft assistance apparatus. Fixing the graft clamp may include inserting the graft clamp into a receiver defined by the clamping segment.

[0014] In some aspects, the method includes making an incision in the blood vessel a the partially occluded portion of the blood vessel. The method may also include grafting the piece of graft material on to the blood vessel at the partially occluded portion of the blood vessel.

[0015] Further, to the extent consistent, any of the embodiments or aspects described herein may be used in conjunction with any or all of the other embodiments or aspects described herein.Brief Description of the Drawings

[0016] Various aspects of the present disclosure are described hereinbelow with reference to the drawings, which are not necessarily drawn to scale, which are incorporated in and constitute a part of this specification, wherein:

[0017] FIG. 1 is a is a diagrammatic representation of an implanted centrifugal flow LVAD;

[0018] FIG. 2 is a set of CT scan images illustrating key anatomical points placed during measurement methods for quantifying pump and outflow graft positioning in accordance with embodiments of the present disclosure;

[0019] FIG. 3 is an image of segmentations of a patient’s aorta, LVAD pump, and outflow graft;

[0020] FIG.4 is an image of the center of the aortic valve identified using the a segmentation based method in accordance with embodiments of the present disclosure;

[0021] FIG. 5 is an image of an aorta and a graft with anastomosis points identified using the a segmentation based method in accordance with embodiments of the present disclosure;

[0022] FIG. 6 is an image of an aorta and a graft with outflow graft angle points identified using the segmentation based method in accordance with embodiments of the present disclosure;

[0023] FIG. 7 is an image of an aorta and a graft with a distance from the graft to the aortic valve identified using the segmentation based method in accordance with embodiments of the present disclosure;

[0024] FIG. 8 is an image of an aorta and a graft with a minor outflow graft angle identified using the segmentation based method in accordance with embodiments of the present disclosure;

[0025] FIG. 9 is an image of an aorta and a graft with a major outflow graft angle identified using the segmentation based method in accordance with embodiments of the present disclosure;

[0026] FIG. 10 is an image of an axial cross-sectional view of a mitral valve with the center o the mitral valve identified using the segmentation based method in accordance with embodiments of the present disclosure;

[0027] FIG. 11A is an image of an aorta and a graft with the anastomosis top identified using a points based method in accordance with embodiments of the present disclosure;

[0028] FIG. 1 IB is an image of an aorta and a graft with the anastomosis bottom identified using the points based method in accordance with embodiments of the present disclosure;

[0029] FIG. 11C is an image of an aorta and a graft with the center of the anastomosis identified using the points based method in accordance with embodiments of the present disclosure;

[0030] FIG. 1 ID is an image of an aorta and a graft with a point for an outflow graft angle identified using the points based method in accordance with embodiments of the present disclosure;

[0031] FIG. 12 is an image of the aortic center at the anastomosis site identified using the pointbased method the points based method in accordance with embodiments of the present disclosure;

[0032] FIG. 13 A is an image of the aortic valve with a center of the aortic valve identified using the point-based method the points based method in accordance with embodiments of the present disclosure;

[0033] FIG. 13B is an image of the aorta with a center of the aorta at the anastomosis identified using the point-based method the points based method in accordance with embodiments of the present disclosure;

[0034] FIG. 14 is an image of a pump of a LVAD implanted in heart with angle point identified using the point-based method the points based method in accordance with embodiments of the present disclosure;

[0035] FIG. 15 is a Histogram for confidence interval range for major outflow angle;

[0036] FIG. 16 is a Histogram for confidence interval range for minor outflow angle;

[0037] FIG. 17 is a Histogram for measurement variation for anastomosis diameter;

[0038] FIG. 18 is a Histogram for measurement variation for valve to graft distance;

[0039] FIG. 19 is a Histogram for measurement variation for inflow depth;

[0040] FIG. 20 is a Histogram for confidence interval range for inflow angle;

[0041] FIG. 21 is a set of Kaplan-Meier curves for correlation of major outflow graft angle compared to adverse events;

[0042] FIG. 22 is a graphical representation of the outflow graft angle range observed in patients in a retrospective study;

[0043] FIG. 23 is a perspective view of a vascular clamp in accordance with embodiments of the present disclosure;

[0044] FIG. 24 is a perspective view of a graft assistance apparatus secured to a vascular clamp in accordance with embodiments of the present disclosure;

[0045] FIG. 25 is an image of rib spreaders in use during LVAD implantation in accordance with embodiments of the present disclosure;

[0046] FIG. 26 is a perspective view of another graft assistance apparatus secured to rib spreaders in accordance with embodiments of the present disclosure;

[0047] FIG. 27 is a perspective view of another graft assistance apparatus secured to an aorta in accordance with embodiments of the present disclosure;

[0048] FIG. 28 is a perspective view of another graft assistance apparatus in accordance with embodiments of the present disclosure;

[0049] FIG. 30 is a perspective view of another graft assistance apparatus in accordance with embodiments of the present disclosure;

[0050] FIG. 31 is a perspective view of the graft assistance apparatus of FIG. 30 secured to a vascular clamp with a graft clamp attached thereto in accordance with embodiments of the present disclosure;

[0051] FIG. 31 is a perspective view of another graft assistance apparatus in accordance with embodiments of the present disclosure;

[0052] FIG. 32 is a perspective view of another graft assistance apparatus in accordance with embodiments of the present disclosure;

[0053] FIG. 33 is a perspective view of the graft assistance apparatus of FIG. 32 secured to a vascular clamp with a graft clamp attached thereto in accordance with embodiments of the present disclosure;

[0054] FIG. 34 is a perspective view of another graft assistance apparatus including a pivot break in accordance with embodiments of the present disclosure;

[0055] FIG. 35 is a perspective view of another graft assistance apparatus including a pivot break in accordance with embodiments of the present disclosure;

[0056] FIG. 36 is a rear perspective view of the graft assistance apparatus of FIG. 35 secured to a vascular clamp with a graft clamp attached thereto in accordance with embodiments of the present disclosure;

[0057] FIG. 37 is a front perspective view of the graft assistance apparatus of FIG. 35 secured to a vascular clamp with a graft clamp attached thereto in accordance with embodiments of the present disclosure;

[0058] FIG. 38 is a perspective view of another graft assistance apparatus including a pivot break in accordance with embodiments of the present disclosure;

[0059] FIG. 39 is a rear perspective view of the graft assistance apparatus of FIG. 38 secured to a vascular clamp with a graft clamp attached thereto in accordance with embodiments of the present disclosure;

[0060] FIG. 40 is a front perspective view of the graft assistance apparatus of FIG. 38 secured to a vascular clamp with a graft clamp attached thereto in accordance with embodiments of the present disclosure;

[0061] FIG. 41 is a top perspective view of the graft assistance apparatus of FIG. 38 secured to a vascular clamp with a graft clamp attached thereto in accordance with embodiments of the present disclosure;

[0062] FIGS. 42A-42D are photographs of other graft assistance apparatuses secured to a vascular clamp clamping an aorta with a graft clamp attached thereto holding a graft at an outflow graft angle in accordance with embodiments of the present disclosure;

[0063] FIGS. 43A-43D are photographs of specimen hearts with grafts implanted thereon at an outflow graft angle in accordance with embodiments of the present disclosure;

[0064] FIG. 44 is a photograph of a specimen in preparation for formalin fixation in accordance with embodiments of the present disclosure;

[0065] FIG. 45 is an image of a specimen heart with angles identified using methods in accordance with embodiments of the present disclosure;

[0066] FIG. 46 is a box and whisker plot for actionable angle across test groups;

[0067] FIG. 47 is a box and whisker plot for outflow major angle across test groups;

[0068] FIG. 48 is a box and whisker plot for graft cut angle across test groups;

[0069] FIG. 49 is a graphical representation of the standard deviations within each experimental, with indicating significantly different variances within that group compared to the control;

[0070] FIG. 50 is a diagrammatic representation of the mounting of a graft assistance apparatus and graft clamp during testing;

[0071] FIG. 51 is a diagrammatic representation of the mounting of a graft assistance apparatus and a vascular clamp during testing; and

[0072] FIG. 52 is a graphical representation of the failure load across 10 trials for each fixation clamp test.Detailed Description

[0073] The present disclosure will now be described more fully hereinafter with reference to example embodiments thereof with reference to the drawings in which like reference numerals designate identical or corresponding elements in each of the several views. These example embodiments are described so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Features from one embodiment or aspect can be combined with features from any other embodiment or aspect in any appropriate combination. For example, any individual or collective features of method aspects or embodiments can be applied to apparatus, product, or component aspects or embodiments and vice versa. The disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. As used in the specification and the appended claims, the singular forms “a,” “an,” “the,” and the like include plural referents unless the context clearly dictates otherwise. In addition, while reference may be made herein to quantitative measures, values, geometric relationships or the like, unless otherwise stated, any one or more if not all of these may be absolute or approximate to account for acceptable variations that may occur, such as those due to manufacturing or engineering tolerances or the like.

[0074] As used herein, the term “clinician” refers to a doctor, a nurse, or any other care provider and may include support personnel.

[0075] In the United States, 300,000 patients suffer from heart failure advanced enough to be eligible for advanced therapies such as full heart transplant. However, there have never been more than 5,000 heart transplants performed in the United States each year. To address the organ short-age, left ventricular assist devices (LVADs) have become a common option for extending life of patients in advanced stages of heart failure. Additionally, many patients are not eligible for heart transplant due to presence of contraindications, and require alternative treatment such as device-based therapy. These therapies include implantation of LVADs. The 2020 Interagency Registry for MechanicallyAssisted Circulatory Support (INTERMACS) reported that 27% of LVAD patients were listed as bridge to candidacy (BTC). The BTC designation indicates that these patients were in advanced heart failure, but were ineligible for transplant. This is a conservative estimate of patients who are contraindicated for heart transplant and thus require LVAD intervention, which entails implantation of a pump into the left ventricle, and rerouting of the blood through an outflow graft out to the aorta. Compared to heart transplants, LVADs are easily accessible and do not lead to host rejection or negative outcomes of immunosuppression. However, the International Society for Heart and Lung Transplantation (ISHLT) reports more than a 90% percent survival rate one year after organ transplant, while even the best estimate of the same metric for LVAD implantation is between 80% percent and 90%. While LVAD implantation is significantly more accessible than heart transplant, LVAD patients still suffer from a range of complications.

[0076] Referring now to FIGS. 1, the current standard for LVADs in the United States is the centrifugal flow LVAD, which is implanted with its inflow cannula inserted into the left ventricle. The pump of the LVAD pulls oxygenated blood from the left ventricle and then reroutes it through an outflow graft into the ascending aorta. Such LVADs are used in treatment for patients with cardiac function so poor that they are not likely to live for more than a matter of months without organ replacement or device-based intervention. Clinicians often recommend that patients be implanted with an LVAD if they fall into Class IV as designated by the New York Heart Association (NYHA) and express the following symptoms: inability to comfortably carry out any physical activity and / or symptoms of heart failure even while resting. In such cases, LVADs are used either as a bridge to transplant (BTT), stabilizing the patient until a donor heart becomes available, bridge to candidacy as mentioned above, or for longer term use as destination therapy (DT).

[0077] While LVADs are an effective means of prolonging survival in patients with end-stage heart failure either as a destination therapy or as a bridge to a heart transplant. Improvements in LVAD technology as resulted in reduced rates of hemocompatibility related adverse events (HRAE), particularly in regards to pump thrombosis. However, the rate of stroke remains substantial. While some of this increased thrombogenicity risk is associated with the design of LVADs, including fluid dynamics inside the device, outflow graft angle with respect to the aorta is associated with higher rates of HRAE. Studies exploring the influence of design and implantation procedures of LVADs and HRAEs are described below.

[0078] In 2020, MOMENTUM 3, a randomized controlled trial conducted by Colombo, et al., compared two LVADs, the HeartMate3 (HM III) to the HeartMate2 (HM II), both available fromAbbott Labs, Chicago, IL, and presented survival without disabling stroke or reoperation at two years. The HM III presented significantly higher survival (76.8% BTT / BCC and 73.2% DT vs 67.3% BTT / BCC and 58.7% DT). Pump thrombosis was also significantly reduced in the HM III (2.4% vs 27.6% in HM II). However, there was no difference between the two devices in reduction of other negative outcomes which impact patient quality of life, including stroke and gastrointestinal bleeding. Additionally, the MOMENTUM 3 trial reports that the HM III and the HM II, which are the leading LVADs in the United States, present stroke risk of 8% to 16% in BTT / BTC patients and 10%-21 % in DT patients. Bleeding was reported in 34%-49% of BTT / BTC patients and 49%-59% of DT patients.

[0079] However, other research has indicated that device design is not the only factor that could be contributing to increased risk of negative patient outcomes. Studies have shown that the specific way a device is deployed within a patient’s anatomy may contribute to this increased risk. Specifically, the angle of the outflow anastomosis has been shown to contribute to risk of stroke. For example, Chiu, et. al. (Chiu WC, Al emu Y, Mclarty AJ, Einav S, Slepian MJ, Bluestein D. Ventricular assist device implantation configurations impact overall mechanical circulatory support system thrombogenic potential. ASAIO J 2017;63:285-92. ) found that a 60-degree outflow angle reduced thrombosis potential. Bhat, et. al. (Bhat S, Mathew J, Balakrishnan KR, Krishna Kumar R. Effect of Outflow Graft Size on Flow in the Aortic Arch and Cerebral Blood Flow in Continuous Flow Pumps: Possible Relevance to Strokes. ASAIO J 2017;63:144-9. htps: / / doi.org / 10.1097 / MAT.000000000000Q507) found that anastomosis sites with a 10 mm diameter were more sensitive to change in angle and associated with negative outcomes than 14 mm diameter grafts. Yoshida, et. al. (Yoshida S, Toda K, Miyagawa S, Yoshikawa Y, Hata H, Yoshioka D, et al. Impact of turbulent blood flow in the aortic root on de novo aortic insufficiency during continuous-flow left ventricular-assist device support. Artificial Organs 2020;44:883-91. htps: / / doi.Org / 10.l 111 / aor. 13671.) also found that angle and position of the outflow graft could impact retrograde flow and cause insufficiency at the aortic valve. Osorio, et. al. (Osorio AF, Osorio R, Ceballos A, Tran R, Clark W, Divo EA, et al. Computational fluid dynamics analysis of surgical adjustment of left ventricular assist device implantation to minimise stroke risk. Comput. Methods Biomech. Biomed. Engin. 2013;16:622-38. https: / / doi.org / 10.1080 / 10255842.2011.629616) performed a computational study which found that an increased outflow angle produced a decrease in embolization of thrombi. Many other studies have also found similar contributions of outflow placement, diameter, and angle towards negative hemodynamics or patient outcomes.

[0080] Influence of outflow graft angle on the occurrence of HRAE remain under investigation by clinicians. However, one obstacle in investigating the outflow graft angle on HRAEs is the lack of surgical tools to allow clinicians to act on guidance on the “proper” outflow graft angle. As such, clinicians tend to only roughly approximate, rather than precisely control, the placement of the outflow graft on the aorta and the optimal angle of the outflow graft, and that they lack control over motion of the aorta and outflow graft due to cardiac contraction and changes in graft properties once the graft is filled with blood. Some studies have shown data that fifty (50) LVADs implanted by a single clinician displayed an outflow graft angle ranging between 62 degrees to 110 degrees, in spite of a statement from that clinician that 45 degrees was the goal outflow graft angle based on training exercises.

[0081] One known shortcoming of current practices for implanting LVADs is kinking in the outflow graft. Kinking in the outflow graft is associated with prevention or slowing of blood flow through the graft to the aorta, which may create negative conditions for the LVAD and also increase risk to the patient. One of the main factors that leads to kinking is the change in mechanical properties that the graft undergoes after being filled with blood, in comparison to being dry and deflated. Clinicians have a variety of approaches for addressing this issue, from soaking the graft in saline to better approximate its final length, to pinching off the end of the graft and allowing it to fill with blood before attaching it. Still, misjudgment of final graft length occurs and both of these methods may add to time that the patient is under anesthesia, which may impact their chance for an ideal recovery and adds to the cost of the procedure.

[0082] Currently, the standard for the portion of attaching the graft to the aorta for of the LVAD implantation procedure is to clamp the aorta with a partial occlusion clamp, make an incision, and visually approximate how and where the outflow graft should be cut. The lack of tools to ensure precision in this attachment may exacerbate kinking. Clinicians struggle with determining the final length of the graft due to changes in properties of the graft in a dry condition versus when the graft is full of blood after implantation. Some clinicians soak the graft in saline prior to use so its behavior will be closer to its filled behavior. Some clinicians clamp off an end of the graft and allow it to fill with blood so they may approximate the proper cutting location, then drain it cut the graft to length and then continue the procedure. Other clinicians leave the graft dry and stretch it to the anastomosis site to make the approximation. Still, graft kinking is a prominent issue caused by excess graft length that results in reduction of flow from the LVAD due to increased pressure. Additional complications due to the graft being too short are still being investigated. For example, an excess of tension at thegraft anastomosis may increase chances of thrombus formation. Further, the length of the graft may alter the outflow graft angle.

[0083] There is wide variability in practices in surgical techniques for implantation of the outflow graft between individual clinicians. To date, no dedicated guidance for outflow graft angle exists. Further, no common method for ensuring clinicians to maintain control over outflow graft orientation exists. Rather, clinicians dictate where and how the outflow graft will be implanted and the criteria forjudging success may be lax and inconsistent. As a result, if a HRAE, e.g., a stroke, is truly related to outflow graft orientation, there is no appropriate technique to mitigate that risk. This illustrates a need for surgical instruments to assist clinicians in measuring and achieving the preoperatively desired outflow graft angle. Without such surgical instruments, insight into the effect of this outflow graft angle on HRAEs may not translate into improvements in achieving preoperative goals and clinical outcomes.

[0084] While some studies have been performed investigating the effects of surgical techniques for outflow grafting during LVAD implantation, the majority of these studies involve the use of computational modeling without validation through patient studies. Thus, there is a need to perform studies to identify correlations between patient-specific anatomy, specific deployment methods, and negative patient outcomes.

[0085] Broadly, this disclosure focusses on quantifying and controlling placement of LVAD outflow anastomosis, including further investigation of correlations between anastomosis placement and negative patient outcomes and the development of a surgical instrument to enable precise control over anastomosis placement. Specifically, described hereinbelow, are devices, systems, and methods for quantification of LVAD pump placement and outflow position and devices, systems, and methods for enabling angular control of an LVAD outflow graft.

[0086] Referring generally to FIG. 2, a set of CT scan images illustrating key anatomical points placed during measurement methods for quantifying pump and outflow graft positioning in accordance with embodiments of the present disclosure is shown. As described above, numerous factors may affect the incidence of outflow graft angle related complications. For example, patient specific fluid dynamics resulting from unique patient anatomy and device implantation may play an important role in these adverse events. The position and angle of the outflow graft, which serves as a conduit to deliver blood from the LVAD to the aorta may be of particular significance. Several studies have highlighted the importance of proper graft orientation, as misalignment may disrupt blood flow patterns, potentially leading to thrombotic complications. Clinicians broadly agree that the geometryand implant location of the inflow cannula is a significant contributor to negative outcomes for patients with LVADs, but a need remains for controlling the geometry of the outflow graft and anastomosis and, by extension, the resulting fluid dynamics through the graft.

[0087] Despite recognition that outflow graft angle is an important factor driving negative outcomes, a standardized and comprehensive method for quantifying LVAD outflow graft orientation is notably absent in clinical practice and scientific literature. Many studies rely on computational or numerical approaches to simulate blood flow through a patient-specific anatomical model. While these models may be enlightening, they rely on many assumptions for material properties and flow boundary conditions. On the other hand, they may also incorporate details and complexities that are challenging to validate. Lastly, these studies are computationally intensive and require collaboration with individuals that have advanced knowledge on computational fluid dynamics, which is not always feasible. Other studies do involve performance of measurements to evaluate LVAD orientation in patients, but a consistent limitation of these studies is the level of detail provided in the description of the measurement method. Several of these studies rely on two dimensional measurements, which involve scrolling to the “best slice” of a volumetric scan and taking a 2D measurement of distance or angle within that slice. This process entails a lot of subjectivity, from choosing a slice to placing points for the measurement. Three-dimensional measurements allow placement of points across image “slices”, but point placement still must be defined in a repeatable manner, otherwise the methods cannot be repeated and relied upon if measurement observer varies within a study group. Therefore, there a need exists to develop a robust and accurate three-dimensional measurement technique that may enhance the reliability of geometric assessments of LVAD orientation. Such a technique may allow for development of personalized LVAD treatments, which may reduce the risks associated with LVAD implantation.

[0088] Referring to FIGS. 2-14, three-dimensional measurement methods for evaluating LVAD orientation on a patient-specific basis are described. Specifically, a segmentation based method (FIGS. 3-10) and a point based method (FIGS. 11-14) was developed. Both methods were used to collect measurements for the same patients. Both methods, their comparison, and the results of a retrospective clinical study are presented and discussed below.

[0089] The patients analyzed by both methods include patients who underwent implantation of a centrifugal flow pump, either the HeartWare Ventricular Assist Device (HVAD; Medtronic Inc, Minneapolis, MN) or the HeartMate 3 (HM III, Abbott Labs, Chicago, IL), within the period of 2016 to 2019 at Houston Methodist Hospital. Those who had undergone an LVAD protocol cardiaccomputed tomography (CT) scan were considered for inclusion in this study. Exclusion criteria encompassed patients with non-contrast studies or those with poor-quality images. Data was primarily derived from an initial contrast-enhanced CT scan of each patient taken following LVAD implantation. This study received institutional IRB approval at Houston Methodist Hospital and patient data was de-identified prior to transfer to Texas A&M University. In assembling patient data, a comprehensive chart review was conducted, covering pre-implant demographics, medical and social history, device type, pertinent clinical variables, post-implant observations, and any documented adverse events. Specially, in this study CT scans were obtained for ninety (90) heart failure patients with LVADs implanted at Houston Methodist Research Hospital. They were analyzed to determine outflow angle. Stroke occurrence within two years of implantation were reported for each patient and statistical tests were performed to identify whether correlations exist between measurements and outcome. Outflow angle was found to be a significant predictor of risk of stroke.

[0090] The principal focus of this analysis centered on adverse neurological events (ANE). For precise evaluation, each outcome was subjected to meticulous scrutiny by a board-certified vascular neurologist. This study excluded cases of acute encephalopathy, delirium without stroke, hemorrhage, and seizures. Ischemic stroke was distinctly characterized as the sudden onset of neurological signs or symptoms that aligned with a focal or multivascular territory within the brain, spinal cord, and retina. Patients who exhibited clinical criteria indicative of ischemic stroke, even in the absence of radiological changes, were also included at the discretion of the reviewing neurologist. Hemorrhage, on the other hand, encompassed categories comprising both asymptomatic and symptomatic intracerebral hemorrhage, subarachnoid hemorrhage, and subdural hemorrhage. Although the primary analysis revolved around ANE, a separate analysis was pre-specified to investigate stroke outcomes, excluding patients who exclusively manifested seizures as ANE. ANE occurrences within 30 days post-implantation were excluded from this analysis. The secondary outcomes under scrutiny included stroke (encompassing both ischemic and hemorrhagic stroke), all-cause mortality, and a composite adverse outcome encompassing ANE, pump thrombosis, gastrointestinal bleeding, and all-cause death.

[0091] Cardiac computed tomography (CT) scans were executed employing a 192-slice dual-source multi-detector third-generation Siemens Somatom FORCE scanner (Siemens Healthineers, Forchheim, Germany). Image acquisition occurred in the craniocaudal direction, commencing from the thoracic inlet and extending to the abdomen, encompassing all pertinent components of the left ventricular assist device (LVAD). The scans were performed utilizing prospective gating at mid-diastole, specifically at 75% of the R-R interval. Subsequently, the image dataset underwent reconstruction at 10% intervals, followed by analysis employing Philips IntelliSpace Portal 9.0 software (Koninklijke Philips Electronics NV, Andover, Massachusetts).

[0092] A measurement methods described herein evaluate LVAD orientation while promoting consistency and repeatability between observers. The measurements as shown FIG. 2 were selected after discussion with a cardiologist at Houston Methodist Research Hospital. The measurements are defined in more detail in Table 1 below.

[0093] These measurements were performed in 3D Slicer, an open-source software that allows for importation and study of medical scans. Measurements for each patient were performed by at least 3 observers so that measurements could be evaluated for consistency and repeatability. Each observer imported data for the patient in question and selected the highest quality diastolic scan by confirming that the mitral valve was fully opened and the aortic valve was fully closed. The observer would then identify and mark points in the scan as shown in Table 2.

[0094] With particular reference to FIGS. 3-9, using the segmentation based method, observers identified point locations by producing segmentations of the outflow graft, aorta, and pump within the best diastolic scan of each patient. Segmentation involves the separation of a digital image into individual segments that may then be treated as digital solid bodies. Each observer would segment the three components from each scan using their own judgment and knowledge of expected patient anatomy. Once the three components were segmented, the observer would place each point listed in Table 1 in the “most appropriate” location on the relevant segmented body using the 3D view in 3D Slicer as shown in FIGS. 4-9.

[0095] Additionally referring to FIG. 10, the only point that was not identified using the segmentations was the Mitral Center. This point was identified by using the axial view of the scan and identifying the plane where the mitral valve began. Then, the observer would scroll through the slices, counting each slice, until the opposite edge of the mitral valve was identified. The slice count was divided by two, then the observer would count back towards the center of the valve until that value was reached, indicating the “middle” of the mitral valve had been located. The observer would place the Mitral Center point at what appeared to be the midpoint between the leaflets visible in the image.

[0096] After all points were placed, 3D Slicer was used to select the key points and measure distances and angles as described in Table 1. Each observer would then record the measurements in a spreadsheet where values could be compared to evaluate the repeatability of the segmentation based method.

[0097] Referring to FIGS. 11-14 the point based method includes placing the key anatomical points listed in Table 2 using the axial, coronal, and sagittal views of each CT scan. The point based method may remove dependence on segmentation and judgment and ability of each observer to place the points around the segmentation accurately.

[0098] The anastomosis superior was found looking at the axial view (FIG. 11). After identifying the anastomosis, the most superior cross section where the outflow graft and the aorta are not in contact was noted and the “anastomosis top” point was placed at the joint.

[0099] The anastomosis inferior was found when looking in the axial view. After identifying the anastomosis, the lowest cross section where the outflow graft and the aorta are in contact was noted and the “anastomosis bottom” point was placed at the joint.

[0100] The aortic valve venter was identified in the coronal view (FIG. 13 A). First, the two leaflets that are in the same cross sections were identified and then the observer scrolled “towards” the third leaflet. After identifying the cross section just before the third leaflet is visible, the point for the aortic valve center was placed at the point between the two visible leaflets.

[0101] The aortic center at graft was found after placing both of the anastomosis points (superior and inferior), by counting the number of cross sections between the most superior and most inferior points. The number of cross sections was divided by two (if odd value, value rounded up), and that value was counted back from the superior anastomosis point towards the inferior anastomosis point and the “Aorta Center at Graft” was placed in the middle of the visible aorta cross section (FIGS. 12 andl3B).

[0102] The outflow graft was labeled by locating the anastomosis within the axial view (FIG. 1 ID). Then the observer moved to a cross section that was at least 20 mm inferior to that point. If 20 mm exactly could not be achieved, the observer chose the next value greater than 20 mm. A point was placed at the center of the graft, and checked by other views to ensure it is aligned with the longitudinal axis of the graft.

[0103] The inflow tip was located in the sagittal view (FIG. 14). First, the cannula edge was identified by moving from left to right through the patient. From that cross section, the number of cross sections it took for the sharp points at the top of the cannula to join again was counted. The number of cross sections was divided by two (if odd value, value rounded up), and that value was counted back towards the center of the inflow cannula. A “inflow tip” point was placed at the midpoint between the two tip edges.

[0104] The inflow base was located in manner similar to the inflow tip. First, in the sagittal view, the pump of the LVAD was located. A point was placed so that it is in line with the axis of the cannula, and at the same “height” in the pump as the first major change in diameter at the base of the inflow cannula. The point was observed in all views to ensure the point is along the axis of the cannula, and is centered.

[0105] The mitral center was located in the axial view. Specifically, the cross section was located where the chamber wall of the heart is separating the atrium and the ventricle. Moving a few cross sections up, a point was placed in the center of the chamber. Two other points were placed, one on top of the chamber and one on the bottom. In approximately every ten cross sections in both directions, the process was repeated, placing two points in the top and bottom, until the valve ends were reached. A “circle” measurement was taken, from all the placed points. These points were then used to calculate the coordinates of the mitral valve center point by averaging all the coordinates in each direction. A new point was placed with those coordinates, as shown in FIG. 14.

[0106] Once the key points were placed in the CT scans of each patient, 3D Slicer annotation tools were used to measure distances and angles between the key points. Each CT scan was measured by the same three observers to help account for interobserver variability and process repeatability errors. Each individual recorded one value for each measurement performed.

[0107] Referring generally to FIGS. 15-22, once measurements were performed, The mean, standard deviation and 95% confidence interval (CI) were provided for each measurement. The relative CI (confidence interval divided by the mean), henceforth referred to as the measurement variation, was evaluated to compare interobserver variability and repeatability of the measurement method. Specifically, Student’s t-tests were performed between the averages of each measurement (across all observers) performed for each method, as well as the measurement variation values for each measurement produced by each method.

[0108] Clinical data related to patient demographics, comorbidities, and adverse events were maintained by Houston Methodist Research Hospital, and analyses related to this data were performed by biostatisticians from that institution. Measurements were completed and compared to patient outcomes as of October 2021. Patients were divided into groups based on occurrence of the outcomes discussed above. Differences between groups were determined by Chi-square or Fisher’s exact tests for categorical variables and Wilcoxon rank-sum test continuous variables as appropriate. The optimal cut point of anastomosis diameter and outflow cannula angle in predicting the primary outcome was determined by the receiver-operating characteristic curve (ROC) analysis with Youdenindex. Incidence of neurologic outcomes were depicted by the Kaplan-Meier curves and stratified by subgroups of outflow cannula angle. Differences between groups was compared by the log-rank test. Cox regression analysis was performed to determine the characteristics associated with having any neurologic outcomes after LVAD implantation. The performance of the measurement method described herein and the method previously used by a cardiology research team at Houston Methodist Research Hospital were compared using the C-statistic improvement. Variables for the multivariable models were selected based on the clinical importance and also by the Stata’s Lasso technique with the cross-validation selection option. The performance of the models was determined by the area under the receiver operating characteristic curve (AUC, for logistic regression models) or Harrell’s C-statistic (for Cox proportional hazard models). All analyses were performed using Stata version 17.0 (StataCorp LLC, College Station, TX, USA). A p value of <0.05 was considered statistically significant.

[0109] With particular reference to FIGS. 15-20, histograms of the measurement confidences for each measurement parameter showing the confidence distribution for each measurement method, with the segmentation based method (shown with upwards hatching) and the points based method (shown with downward hatching). As shown, point-based measurement method consistently produced measurement confidences at 10% or below, while the segmentation-based method may result in a higher ranging of measurement confidences depending on parameter is under review. Results of the Student’s t-tests comparing measurement averages and confidences between each measurement method which indicated statistically significant differences in the segmentation based method (Table 3) and the points based method (Table 4) are shown in Tables 3 and 4 below.

[0110] As shown in FIGS. 15-20 and Tables 3 and 4, the point based method tended to yield measurements within the acceptable statistical threshold more consistently than the segmentation based method. When the segmentation based method was employed, the measurement confidences for this parameter exhibited a considerable range, spanning from just over 10% to exceeding 105% across observers for a single patient. This variability may be attributed to the fact that the inflow angle may be quite small in certain patients, at times measuring less than 5 degrees. Consequently, even slight variations in recorded values among different observers could result in extremely high measurement confidence values (indicating high inconsistency) for this parameter.

[0111] FIGS.15-20 demonstrate that the Point-Based Method consistently yielded measurement confidences within the threshold of acceptance for each parameter. Specifically, concerning pertinent parameters such as distance from aortic valve to the graft, outflow angle, anastomosis diameter, and inflow depth, the points-based method consistently yielded acceptable measurement confidences for 100% of the scans.

[0112] Of the ninety (90) patients in the study, twenty patients had 32 adverse events, including stroke (ischemic n=9, ischemic with hemorrhagic conversion n=3, ischemic stroke with sub arachnoid hemorrhage n= 2), hemorrhage (intracerebral hemorrhage n=5, subdural hemorrhage n=2), and seizures (n=5). The median time between implantation and occurrence of an adverse event was 7 months. Six patients experienced more than one adverse event. Five patients died as a result of the adverse event for which they were admitted to the hospital. Forty-eight patients experienced composite adverse outcomes, with 18 experiencing stroke, 10 experiencing pump thrombosis, 16 experiencing GI bleeding, and 24 dying within the study time frame.

[0113] LVAD outflow graft angles measured with the point based method described above were significantly different in patients with and without adverse events. Greater angles were associated with higher risk of adverse events. The average outflow graft angle in the group with no adverse events was 77.4 (73.4 - 82.8) degrees, whereas the average angle in the group with adverse events was 86.7 (80.3 - 91.9) (p=0.01). When analyzing only correlations related to stroke, the average angle in non-stroke patients was 78.1 (73.5 - 82.9) degrees and 85.2 (80.1 - 92.8) degrees in stroke patients (p=0.01). The outflow graft angles showed a statistically significant difference for the composite outcome, measuring 73.4 (68.9 - 82.9) degrees on average in outcome-free patients versus 81.5 (76.4 - 88.8) degrees in patients who experienced outcomes (p=0.03).

[0114] Receiver Operating Characteristics (ROCs) were constructed for the angle measurements in order to determine the optimal angle cut offs for the study population. The optimal angle cut off wasfound to be 83 degrees with the best discrimination for occurrence of adverse events vs no events recorded (AUC = 0.73 for both adverse neurological events and stroke). Based on that optimal cut off angle, patients with a measured major angle less than 83 degrees were at a significantly lower risk level of adverse neurological events (Hazards ratio for adverse neurological events and stroke 4.43 (1.51-13.02) and 1.21 (0.48, 3.01), respectively, as shown in the Kaplan-Meier survival curve (FIG. 21). The outflow graft angle remained a significant predictor of composite outcome as well, with hazards ratio HR 2.80 (1.26 -6.2) respectively but not for all-cause death (FIG. 21).

[0115] As discussed above, patient-specific LVAD orientation is a potential influence on risk of negative outcomes, such as stroke, in heart failure patients with this device-based therapy. Specifically, the measurement methods as described above showed that outflow graft angle may be a significant predictor of risk of stroke and other negative outcomes. Despite the associated complications with outflow graft angle, current surgical methods result in a large outflow graft angle range across patients, even when the procedure is performed by the same clinician. These factors indicate that outflow graft attachment in LVAD patients could be in need of improvement to provide clinicians with more control to produce their desired outflow graft angle. Further, repeatable production of outflow graft angles may allow clinicians to quantify an “ideal” outflow angle to reduce the occurrence negative outcomes.

[0116] Referring to FIG. 22, histograms of anastomosis diameter, major outflow angle, and minor outflow angle in forty (40) patients with LVADs are shown. This data was acquired using the methods described above. The range for major outflow angle is as large as 50 degrees, while the range for minor outflow angle is as large as 40 degrees. This is the case despite the clinicians that implanted the LVADs indicating an preoperative plan to position the outflow graft approximately 45 degrees relative to the ascending aorta. While more analysis is necessary before concluding that any particular angle is ideal with regard to patient outcome, it is clear that the conditions at the anastomosis site during surgery prevent clinicians from deploying the outflow graft as planned prior to the surgery. Such conditions that may limit the ability of the clinician to visually determine the outflow graft angle may include, but is not limited to, limited visibility of the aorta or motion of the aorta or graft due to beating of the heart.

[0117] Referring to FIG. 23, current standard for creating the outflow graft anastomosis during LVAD implantation includes the use of a vascular clamp 10, e.g., a partial occlusion clamp, to partially occlude the aorta, create the incision in the occluded area, visually approximate how and where the outflow graft should be cut, and suture the outflow graft without allowing blood to leavethe site. The occlusion is created by the occlusion portion 12 of the vascular clamp 10. Mor This procedure provides clinicians little to no control over outflow graft angle when implanting LVADs in heart failure patients, and they also have minimal control over precise and correct length of the outflow graft in order to prevent kinking or tension on the anastomosis site. As such, a need exists for surgical devices that allow for clinicians to control the outflow graft angle. Further, such surgical devices should be low cost, intuitive for clinicians to integrate into existing practices, an allow for flexibility in placement of the anastomosis along the aorta.

[0118] Referring generally to FIGS 24-42, several graft assistance apparatuses in accordance with embodiments of the present disclosure are described hereinbelow. Each of the graft assistance apparatuses described herein are configured to assist clinicians in controlling the outflow graft angle of a graft during a LVAD implantation procedure. Each of the graft assistance apparatuses may be disposable or sterilizable. A kit including a vascular clamp, a graft clamp, and one or more of the graft assistance apparatus is contemplated in accordance with embodiments disclosed herein. The kit may be aseptically sealed with a vascular clamp, a graft clamp, and one or more of the graft assistance apparatus contained therein for use during an LVAD implantation procedure.

[0119] Referring now to FIG. 24 an example graft assistance apparatus 100 in accordance with embodiments of the present disclosure is shown. The graft assistance apparatus 100 includes a securement segment 110, and arm 120, and angle readout 130, and a graft clamp 140. The securement segment 110 secures the graft assistance apparatus 100 to a body portion 14 of the vascular clamp 10. More specifically, the securement segment 120 defines a securement axis S-S. The securement segment 110 may is secured to the body portion 14 with the securement axis S-S parallel to a longitudinal body axis L-L of the body portion 14, as shown. The arm 120 extends from the securement segment 110. The arm 120 may be adjustable to position the graft clamp 140 relative to an incision location on the aorta. The angle readout 130 indicates the out flow angle of a piece of graft material clamped by the graft clamp 140 relative to the occluded portion of the aorta when the vascular clamp 10 clamps on the aorta. The graft clamp 140 is configured to grip the piece of graft material and seal an entire diameter of the graft. Sealing the entire diameter of the graft may allow for the graft to be filled with blood or saline to allow a clinician to estimate the final length of the graft. The graft clamp 140 defines a receiver axis G-G. The graft clamp 140 may be adjustable to adjust a graft angle a defined between the receiver axis and an occlusion axis 0-0 of the occlusion portion 12. The occlusion portion 12 may extend from the body portion 14 about the occlusion axis O-O. The occlusion axis 0-0 may be at an angle in a range of 0 degrees to 90 degree, e.g., 30, 40, 45, 60, or 90degrees, from the longitudinal body axis L-L of the body portion 14. The graft angle a may be calibrated to correspond to the outflow graft angle of the graft material.

[0120] Referring to FIGS. 25 and 26, another example graft assistance apparatus 200 in accordance with embodiments of the present disclosure is shown. The current standard for allowing access to the surgical volume during LVAD implantation and other invasive cardiac procedures is to saw through the patient’s ribs and then install rib spreaders 20 to hold them open to ensure the clinician has as much access to the surgical site as possible. The graft assistance apparatus 200 is attached to the rib spreaders 20 and the clinician may position the graft as desired relative to the aorta. The graft assistance apparatus 200 includes a graft securing arm 210 and an angle arm 220. The graft securing arm 210 is and adjustable arm used to clamp the outflow graft. The graft securing arm 210 is flexible but resists forces that would result in unintentional adjustments. The angle arm 220 is used to hold an optical guide, e.g., a protractor, for indicating the axis of the ascending aorta and the relative angle of the outflow graft. The angle arm 220 is flexible but resists forces that would result in unintentional adjustments.

[0121] Referring to FIG. 27, another example graft assistance apparatus 300 is in accordance with embodiments of the present disclosure is shown. The graft assistance apparatus 300 removably secures directly to the ascending aorta. The graft assistance apparatus 300 includes hooks 310, an angle guide 320, and a graft clamp 330. The hooks 310 secure the graft assistance apparatus 300 to the aorta. The hooks 310 may wrap around the posterior side of the aorta to secure the graft assistance apparatus 300 thereto. In embodiment, the hooks 310 may be replaced with a strap. The angle guide 320 shows a clinician the approximate outflow graft angle relative to the ascending aorta. The graft clamp 330 holds the outflow graft at the desired outflow graft angle. The graft clamp 330 may be slidingly attached to the angle guide 320. In such an embodiment, the graft clamp 330 may slide to the desired outflow graft angle along the angle guide 320.

[0122] Referring to FIG. 28, another example graft assistance apparatus 400 in accordance with embodiments of the present disclosure is shown. The graft assistance apparatus 400 includes a clip 410 and a graft clamp 420. The clip 410 is configured to secure the graft assistance apparatus 400 to the vascular clamp 10. The clip 410 defines a securement axis S-S that may be parallel to longitudinal body axis L-L of the body portion 14 of the vascular clamp 10 when secured thereto. The graft clamp 420 is configured to clamp the graft during an surgical procedure. The graft clamp 420 may be disposed on an end of an arm 430. The graft clamp 420 may be movably disposed on the end of the arm 430 to selective adjust the outflow graft angle of the piece of graft material clamped thereinrelative the aorta during surgical procedure. The graft clamp 420 may define a receiver axis G-G. The receiver axis G-G may The receiver axis G-G may be perpendicular to the securement axis.

[0123] Referring to FIGS. 29 and 30, another example graft assistance apparatus 500 in accordance with embodiments of the present disclosure is shown. The graft assistance apparatus 500 includes a clip 510, an arm 520, and a graft clamp fixture 530. The clip 510 is configured to secure the graft assistance apparatus 500 to the vascular clamp 10. The clip 510 defines a securement axis S-S that may be parallel to the longitudinal body axis L-L of the body portion 14 of the vascular clamp 10 when secured thereto, as shown in FIG. 30. The clip 510 may removably secure to the arm 520 and the vascular clamp 10. As such, the graft assistance apparatus 500 may be moved closer or farther from the occlusion portion 12 of the vascular clamp 10. The graft clamp fixture 530 may secure a graft clamp 540 to the graft assistance apparatus 500. The graft clamp 540 may be a conventional hemostat or other atraumatic vascular clamp for holding the graft. The graft clamp fixture 530 may be configured for adjustment of the graft clamp 540 relative the occlusion portion 12 of the vascular clamp 10 and, thus, the aorta. The graft clamp fixture may define a receiver axis G-G. Adjustment of the graft clamp fixture 530 may allow the adjustment of the graft angle a with respect to the occlusion axis 0-0 defined by the occlusion portion 12.

[0124] Referring to FIG. 31, another graft assistance apparatus 600 in accordance with embodiments of the present disclosure is shown. The graft assistance apparatus 600 includes a securement segment 620 and a clamping segment 640. The securement segment 620 and the and clamping segment 640 are pivotally coupled to each other about a pivot axis P-P. The securement segment 620 secures the graft assistance apparatus 600 to the vascular clamp 10. The securement segment 620 may include a securement arm 622 that extends therefrom and is configured to secure the graft assistance apparatus 600 to the vascular clamp 10. The securement arm 622 defines a passage 624 about a securement axis S-S. The clamping segment 640 defines a receiver 642 that receives a graft clamp 660, e.g., a bulldog clamp, (FIG. 33). The graft clamp 660 may define a clamp axis C-C along its longitudinal length. The receiver 642 is defined about a receiver axis G-G. When the graft clamp 660 is within the receiver 642, the receiver axis G-G and the clamp axis C-C may be parallel. In some embodiments, the clamp axis C-C and the receiver axis G-G may be colinear. The receiver axis G-G may intersect the securement axis S-S or the pivot axis P-P. When the securement segment 620 is secured to the vascular clamp 10, the clamping segment 640 may be pivoted about the pivot axis P-P to selectively position the graft clamp 660 with respect to the vascular clamp 10. Specifically, when the clamping segment 640 is pivoted about the pivot axis P-P the graft angle a may be adjusted.In such embodiments, the graft angle a may be defined between the clamp axis C-C and the occlusion axis 0-0.

[0125] Referring to FIGS. 32 and 33, another graft assistance apparatus 700 in accordance with embodiments of the present disclosure is shown. The graft assistance apparatus 700 includes a securement segment 720 and a clamping segment 740. The securement segment 720 and the and clamping segment 740 are pivotally coupled to each other about a pivot axis P-P. The pivot axis P-P of the graft assistance apparatus 700 may be located centrally along a length of the clamping segment 740. Locating the pivot axis P-P centrally along the clamping segment 740 may shorten the moment arm of the clamping segment 740 and aid in adjusting the clamping segment 740 relative to the vascular clamp 10. The securement segment 720 secures the graft assistance apparatus 700 to the vascular clamp 10. The securement segment 720 may include a securement arm 722 that extends therefrom and is configured to secure the graft assistance apparatus 700 to the vascular clamp 10. The securement arm 722 may extend directly, e.g., straight outward, from the securement segment 720, as shown in FIG. 32. In some embodiments, the securement arm 722 may extend from the securement segment 720 at an offset angle from a first or front surface 721 of the securement segment 720, as shown in FIGS. 33, 35, and 38. The offset angle may be in a range of 5 degrees to 90 degrees, e.g., 20 degrees, 35 degree, 45 degrees, or 75 degrees. In such embodiments, the offset securement arm 722 may secure the securement segment 720 to the vascular clamp 10 such that the front surface 721 is parallel to the occlusion portion 12 of the vascular clamp 10. Specifically, the offset securement arm 722 may secure the securement segment 720 to the vascular clamp 10 such that the front surface 721 is parallel to occlusion axis O-O. In certain embodiments, the securement arm 722 may include a lock knob 723 configured to lock the position of the graft assistance apparatus 700 on the vascular clamp 10, as shown in FIG. 33. The securement arm 722 defines a passage 724 about a securement axis S-S. When the securement arm 722 is secured to the body portion 14 of the vascular clamp 10 the securement axis S-S may be parallel the body portion 14. The clamping segment 740 defines a receiver 742 that receives the graft clamp 660. The receiver 742 defines a receiver axis G-G. The graft angle a may be defined between the clamp axis C-C and the occlusion axis O-O. When the securement segment 720 is secured to the vascular clamp 10, the clamping segment 740 may be pivoted about the pivot axis P-P to selectively position the graft clamp 660 with respect to the vascular clamp 10. Specifically, the graft angle a may be adjusted by pivoting the clamping segment 740. When the graft clamp 660 clamps a piece graft material, a given graft angle a may correspond to anoutflow graft angle of the piece of graft material when the piece of graft material is grafted to the aorta.

[0126] Referring to FIG. 34, another graft assistance apparatus 800 in accordance with embodiments of the present disclosure is shown. The graft assistance apparatus 800 is substantially similar to the graft assistance apparatus 600. For reasons of brevity only differences between the graft assistance apparatus 800 and the graft assistance apparatus 600 will be described with like elements given like terms and labels with the leading “6” replaced with a leading “8”. The graft assistance apparatus 800 includes a securement segment 820, a clamping segment 840, and a pivot break 850. The securement segment 820 and the and clamping segment 840 are pivotally coupled to each other about a pivot axis P-P. The securement segment 820 secures the graft assistance apparatus 800 to the vascular clamp 10. The securement segment 820 may include a securement arm 822 that extends therefrom and is configured to secure the graft assistance apparatus 800 to the vascular clamp 10. The clamping segment 840 defines a receiver 842 that receives the graft clamp 660. When the securement segment 820 is secured to the vascular clamp 10, the clamping segment 840 may be pivoted about the pivot axis P-P to selectively position the graft clamp 660 with respect to the vascular clamp 10. The pivot break 850 selective fixes the rotational position of the clamping segment 840. The pivot break 850 include a clutch 852 and a prong 854. The clutch 852 may be disposed on the securement segment 820. The clutch 852 may define a plurality of notches 856 that may receive the prong 854 therein. The prong 854 may be disposed on the clamping segment 840. When the clamping segment 840 pivots about the pivot axis P-P, the prong 854 may be received within a respective notch 856 to rotationally fix the clamping segment 840 relative to the securement segment 820. In such embodiments, each respective notch 856 may correspond to a respective outflow graft angle.

[0127] Referring to FIGS. 35-37, another graft assistance apparatus 900 in accordance with embodiments of the present disclosure is shown. The graft assistance apparatus 900 is substantially similar to the graft assistance apparatus 700. For reasons of brevity only differences between the graft assistance apparatus 900 and the graft assistance apparatus 700 will be described with like elements given like terms and labels with the leading “7” replaced with a leading “9”. The graft assistance apparatus 900 includes a securement segment 920, a clamping segment 940, and a pivot break 950. The securement segment 920 and the and clamping segment 940 are pivotally coupled to each other about a pivot axis P-P. The pivot axis P-P of the graft assistance apparatus 900 may be located centrally along a length of the clamping segment 940. Locating the pivot axis P-P centrally along the clamping segment 940 may shorten the moment arm of the clamping segment 940 and aid in adjustingthe clamping segment 940 relative to the vascular clamp 10. The securement segment 920 secures the graft assistance apparatus 900 to the vascular clamp 10. The securement segment 920 may include a securement arm 922 that extends therefrom and is configured to secure the graft assistance apparatus 900 to the vascular clamp 10. The clamping segment 940 defines a receiver 942 that receives the graft clamp 660. When the securement segment 920 is secured to the vascular clamp 10, the clamping segment 940 may be pivoted about the pivot axis P-P to selectively position the graft clamp 660 with respect to the vascular clamp 10. The pivot break 950 selective fixes the rotational position of the clamping segment 940. The pivot break 950 includes a clutch 952 and a prong 954. The clutch 952 may be disposed on the securement segment 920. The clutch 952 may define a plurality of notches 956 that may receive the prong 954 therein. The clutch 952 may have a circular profile, as shown in FIG. 35. In some embodiments, the clutch 952 may have a semicircular profile, as shown in FIGS. 36 and 37. The notches 956 may extend entirely around the circumference or perimeter of the clutch 952 or may extend less than the entire perimeter. The prong 954 may be disposed on the clamping segment 940. When the clamping segment 940 pivots about the pivot axis P-P, the prong 954 may be received within a respective notch 956 to rotationally fix the clamping segment 940 relative to the securement segment 920. In such embodiments, each respective notch 956 may correspond to a respective outflow graft angle.

[0128] Referring to FIGS. 38-39, another graft assistance apparatus 1000 in accordance with embodiments of the present disclosure is shown. The graft assistance apparatus 1000 is substantially similar to the graft assistance apparatus 900. For reasons of brevity only differences between the graft assistance apparatus 1000 and the graft assistance apparatus 900 will be described with like elements given like terms and labels with the leading “9” replaced with a leading “10”. The graft assistance apparatus 1000 includes a securement segment 1020, a clamping segment 1040, and a pivot break 1050. In some embodiments, the graft assistance apparatus 1000 may be a transparent or translucent material to minimize visual obstructions to the clinician. The securement segment 1020 and the and clamping segment 1040 are pivotally coupled to each other about a pivot axis P-P. The pivot axis P- P of the graft assistance apparatus 1000 may be located centrally along a length of the clamping segment 1040. Locating the pivot axis P-P centrally along the clamping segment 1040 may shorten the moment arm of the clamping segment 1040 and aid in adjusting the clamping segment 1040 relative to the vascular clamp 10. The securement segment 1020 secures the graft assistance apparatus 1000 to the vascular clamp 10. The securement segment 1020 may include a securement arm 1022 that extends therefrom and is configured to secure the graft assistance apparatus 1000 to the vascularclamp 10. The arm 1022 defines passage 1024 about a securement axis S-S. When the securement arm 1022 is secured to the body portion 14 of the vascular clamp 10 the securement axis S-S may be parallel the body portion 14. Specifically, the securement axis S-S may be parallel to the longitudinal body axis L-L. In some embodiments, the securement axis S-S and the longitudinal body axis L-L may be colinear. The clamping segment 1040 defines a receiver 1042 that receives the graft clamp 660. The receiver 1042 is defined about a receiver axis G-G. The graft angle a may be defined between the clamp axis C-C and the occlusion axis O-O. When the securement segment 1020 is secured to the vascular clamp 10, the clamping segment 1040 may be pivoted about the pivot axis P- P to selectively position the graft clamp 660 with respect to the vascular clamp 10. Specifically, the graft angle a may be adjusted by pivoting the clamping segment 1040. When the graft clamp 660 clamps a piece graft material, a given graft angle a may correspond to an outflow graft angle of the piece of graft material when the piece of graft material is grafted to the aorta.

[0129] The pivot break 1050 selective fixes the rotational position of the clamping segment 1040. The pivot break 1050 includes a clutch 1052 and a prong 1054. The clutch 1052 may be disposed on the securement segment 1020. The clutch 1052 may define a plurality of notches 1056 that may receive the prong 1054 therein. The clutch 1052 may have an arcuate profile, as shown in FIG. 38. The prong 1054 may be disposed on the clamping segment 1040. When the clamping segment 1040 pivots about the pivot axis P-P, the prong 1054 may be received within a respective notch 1056 to rotationally fix the clamping segment 1040 relative to the securement segment 1020. In such embodiments, each respective notch 1056 may correspond to a respective outflow graft angle. The notches 1056 may include outflow angle indicators 1058. The outflow angle indicators 1058 may indicate the outflow graft angle of a piece of graft material held in the graft clamp 660 relative to the aorta when the vascular clamp 10 is clamped thereon.

[0130] Referring to FIG. 42A-42D, other graft assistance apparatuses 1100a, 1100b, 1100c, and HOOd in accordance with embodiments of the present disclosure are shown. The graft assistance apparatuses 1100a, 1100b, 1100c, and HOOd are configured to hold the graft clamp 660 at a fixed angle with respect the occlusion portion 12 of the vascular clamp 10. The fixed angle may be in a range of 30 degrees to 90 degrees, e.g., 45 degrees. Moreover, when the vascular clamp 10 is clamped on the aorta 1102, with the occlusion portion 12 substantially parallel to the longitudinal axis of the aorta 1102, and the graft clamp 660 may hold the graft 1104 at fixed angel to set the outflow graft angle of the graft 1104, as shown in FIGS. 42A-42D. For example, in FIG. 42A, the graft assistance apparatus 1100a is shown holding the graft 1104 an outflow graft angle of 40 degrees with respect tothe aorta 1102. In FIG. 42B, the graft assistance apparatus 1100b is shown holding the graft 1104 an outflow graft angle of 50 degrees with respect to the aorta 1102. In FIG. 42C, the graft assistance apparatus 1100c is shown holding the graft 1104 an outflow graft angle of 60 degrees with respect to the aorta 1102. In FIG. 42D, the graft assistance apparatus 1 lOOd is shown holding the graft 1104 an outflow graft angle of 70 degrees with respect to the aorta 1102. As shown, the graft angle a of each of graft assistance apparatuses 1100a, 1100b, 1100c, and HOOd is calibrated to correspond to an outflow graft angle of the aorta 1102. For example, when the vascular clamp 10 is clamped on the aorta with the occlusion axis 0-0 substantially parallel to a longitudinal axis of the aorta 1102, as shown, the graft angle a and the outflow graft angle defined between the piece of graft material 1104 and the aorta 1102 may be complementary angles, e.g., angles that sum to 90 degrees. In such an embodiment, the graft material 1104 may be clamped by the graft clamp 660 with a longitudinal axis of the piece of graft material 1104 substantially perpendicular to the clamp axis C-C. In embodiments, the graft angle a and the outflow graft angle may be equal to each other. For example, in embodiment where the graft angle a is 45 degrees, the outflow graft angle may also be 45 degrees. In some embodiments, the graft angle a and the outflow graft angle may different. For example, in embodiment where the graft angle a is 30 degrees, the outflow graft angle may be 60 degrees.

[0131] Although the method steps are described in a specific order, it should be understood that other steps may be performed in between described steps, described steps may be adjusted so that they occur at slightly different times, or the described steps may occur in any order unless otherwise specified.

[0132] While several embodiments of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Any combination of the above embodiments is also envisioned and is within the scope of the appended claims. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope of the claims appended hereto.

[0133] Referring now to FIGS. 43-49, experimental procedures and results of implantation of several grafts using a graft assistance apparatus, e.g., the graft assistance apparatus 1000, in accordance with embodiment of the present disclosure are described. In the experiment, twelve pig hearts and the attached aortic arches were procured from the Texas A&M Meat Sciences program. These specimens were harvested directly from slaughter. Specimens were originally delivered withheart, aorta, trachea, lungs, and connective tissue still intact. The hearts and aortas were isolated and separated from the rest of the tissue, which was then disposed of. The specimens were bagged and stored at 4 degrees Celsius until the time of testing. Four Texas A&M veterinarians and veterinary residents (Veterinarian 1, Veterinarian 2, and Residents) volunteered to assist and offer their surgical training. Each veterinarian worked individually while the residents worked as a pair. For each specimen, the veterinarians and residents attached a vascular graft to the ascending aorta following their study of the performance of this procedure in humans using publicly available video footage the human procedures.

[0134] As shown in FIG. 43A-43D, The specimens were divided into 4 Test Groups - the latest prototype for each angle was used in the procedure: 80 degrees (FIG. 43C), 60 degrees (FIG. 43B), and 40 degrees (FIG. 43 A). For the Control Group (FIG. 43D) no graft assistance device was used. The veterinarians were asked to estimate a 45-degree outflow angle, per testimony from cardiothoracic clinicians who are experienced in the procedure.

[0135] Veterinarian 1, Veterinarian 2, and the pair of residents each performed the procedure on one specimen in the control group and each of the test groups. The following procedure was followed for each specimen: A 32-quart plastic bin was padded with wet paper towels to provide some stabilization of the specimen. A heart with aorta was placed into the bin, along with a partial occlusion clamp and a 15-30 cm segment of vascular graft. A variety of diameters and brands of grafts were used after they were donated by the Center for Device Innovation. The clinician placed the partial occlusion clamp onto the ascending aorta, attempting to clamp parallel to the edge of the vessel. The vascular graft was submerged in water to simulate being wet with blood, to allow as similar a behavior as possible.

[0136] For the test groups, the appropriate graft assistance apparatus and an atraumatic vascular clamp were provided. The atraumatic vascular clamp was applied to an end of the vascular graft, perpendicular to the graft. The graft assistance apparatus was snapped onto the partial occlusion clamp and slid up the clamp to ensure a secure fit. The atraumatic vascular clamp was slid into its slot in the graft assistance apparatus. The graft was stretched gently across the clamped edge of the aorta, then cut parallel to that edge.

[0137] For the control group, the clinician was asked to cut the end of the graft at their best estimate of a 45 degree angle. An incision the same length as half the circumference of the cut end of the graft was made in the clamped edge of the aorta. The cut edge of the graft and the incision in the aorta were sutured together using 5-0 Redilene polypropylene suture. After the attachment was created, allclamps and prototypes were removed. Final suturing was performed if necessary to ensure the attachment was secure.

[0138] The vascular graft was allowed to drape naturally on the heart, and then it was cut and sutured approximately halfway between the anastomosis and the apex of the heart. Extra graft was cut off. This was done to preserve graft material as well as ensure that the anastomosis would not be unintentionally manipulate during transportation and preparation and performance of imaging.

[0139] Imaging of the specimens was performed by the Texas A&M Cardiovascular Pathology Laboratory. After the specimens were retrieved from testing, they were cleaned (flushed, and connective tissue was removed) to improve quality of imaging. The apexes were cut to enable more stability when they were then suspended upright (apex-side pointed down) in buckets to ensure the aorta, graft, and anastomosis would not be disturbed before or during fixation. Formalin was poured into the buckets, then drained. The formalin remaining on the specimen was left to set for multiple days prior to imaging, as shown in FIG. 44.

[0140] Referring to FIG. 45, image files were received from the Cardiovascular Pathology Lab for analysis. These images were then loaded into 3D Slicer. As shown, the outflow graft angle was measured using methods described herein: actionable angle, outflow major angle, and graft cutoff angle.

[0141] In measuring the actional able, the most superior and inferior points of the attachment between the outflow graft and the aorta was identified. The center point between the two was also identified. The image slice 2 centimeters inferior from the center point was located, and a point was placed at the medial edge of the outflow graft cross section and the aorta cross section. The lines from the graft to the inferior attachment point, and the aortic edge and the inferior attachment point produced the actionable angle.

[0142] In measuring the outflow major angle, the method used was the same as described above. At the center point of the anastomosis, a point was also placed in the center of the aorta. Two centimeters inferior from the center point of the anastomosis, a point was placed in the center of the outflow graft. The angle from the outflow graft point to the center of the aorta at the anastomosis and down to the center of the distal aorta is the outflow major angle.

[0143] Referring now to FIGS. 46-49, box and whisker plots are shown for the angles analyzed for each specimen, as shown in FIGS. 46-48, and standard deviations are graphically shown between specimen in each group in FIG. 49. While the groupings may not be quite at the desired angles based on the devices used for each test group, the angles produced by each device had clear separation of atleast 10 degrees, and within 10 degrees of the desired angle, even including variation in clinician performing the procedure. In contrast, the control groups consistently show at least 20-degree variations, and none of them come close to the desired angle of 45 degrees.

[0144] Paired Samples T-Tests were performed between each test group. Each pair was found to be statistically significant, with p-values of <0.001 (40 vs 60), 0.007 (40 vs 80), and 0.031 (60 vs 80), indicating that a significant difference was found between each group. F tests were also performed to determine which groups had statistically significantly different variations compared to the control group.

[0145] With reference to FIGS. 50-52, experimental procedures and results of the ability of the graft assistance apparatuses described herein to fix graft clamps and atraumatic vascular clamps under the range of forces that could be expected throughout the creation of the outflow anastomosis during LVAD implantation are described.

[0146] Particularly referring to FIG. 50, the fixation of a graft clamp was experimentally tested. The independent variable was displacement (mm) - change in position between the graft assistance apparatus and the graft clamp. The dependent variable was force (N) - tension applied to the attachment between the graft assistance apparatus and the graft clamp. Review of relevant literature found that forces during suturing and sharp penetration of vascular tissue fell within 5 + / - 5 Newtons. Because of this, an acceptance criteria for the following experimental procedure of 10N maximum force was identified. The procedure includes:• Install the clamp into the prototype.• Mount the base fixture to the test frame base with 10-32 screws.• Mount the hook fixture to the actuator.• Secure the prototype to the base fixture with zip ties.• Lower the actuator until the hook can be secured around the spring on the clamp. See FIG. 50.• Run the test protocol.• Raise the actuator at a rate of 2 inches per minute.• Record the maximum force before separation between the clamp and prototype component.

[0147] Referring to FIG. 51, the fixation of a vascular clamp, e.g., a partial occlusion clamp, was experimentally tested. The independent variable was displacement (mm) - change in position between the graft assistance apparatus and the vascular clamp. The dependent variable was force (N) - tension applied to the attachment between the graft assistance apparatus and the vascular clamp. Review of the relevant literature found that forces during suturing and sharp penetration of vascular tissue fellwithin 5 + / - 5 Newtons. Because of this, an acceptance criteria for the following experimental procedure of ION maximum force was identified. The procedure includes:• Install the clamp into the prototype.• Mount the base fixture to the test frame base with 10-32 screws.• Mount the hook fixture to the actuator.• Secure the prototype to the base fixture with zip ties.• Lower the actuator until the hook can be secured around the spring on the clamp. See FIG. 51.• Run the test protocol.• Raise the actuator at a rate of 2 inches per minute.• Record the maximum force before separation between the clamp and prototype component.

[0148] Referring to FIG. 52, testing of the graft clamp fixation was performed on a Mark- 10 testing frame with an M5-500 force gauge. Ten trials were performed and the fixation force exceeded IO N for every trial. For one trial, the force was allowed to reach 30 N before the test was stopped to avoid failure of the testing fixtures or of the graft clamp (atraumatic vascular clamp) itself.

[0149] Due to technical limitations, testing the fixation of the vascular clamp (partial occlusion clamp) as described above could not be carried out precisely. It was replicated instead as shown herein, by weighing down the fixture for the partial occlusion clamp, installing the device with a ziptie loop, and using a fishing scale hooked around the zip tie to apply force. Force was slowly increased until 10 N was exceeded, 10 times in a row. The device remained fixed to the partial occlusion clamp throughout testing, showing it may meet the acceptance criteria explained in the testing protocol above.

[0150] The description of the embodiments as set forth herein is illustrative and non-limiting and modifications to structure, dimensions, materials, and methodologies may be made without departing from the scope of the present teachings. Features of various embodiments may be combined with other embodiments within the contemplation of this disclosure. Variations and modifications of the embodiments disclosed herein are possible and practical alternatives to and equivalents of the various elements of the embodiments would be understood to those of ordinary skill in the art upon study of this disclosure. While several embodiments of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the foregoing description should not be construed as limiting, but merely as exemplifications of particularembodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.

Claims

What is Claimed:

1. A system for implanting a graft, the system comprising: a vascular clamp including body portion and an occlusion portion extending from the body portion, the occlusion portion configured to clamp a blood vessel to at least partially occlude a portion of the blood vessel, the body portion disposed along a longitudinal body axis and the occlusion portion disposed along an occlusion axis, the occlusion axis offset from the longitudinal body axis in a range of 0 degrees to 90 degrees; a graft clamp configured to clamp a piece of graft material therein, the graft clamp disposed along a clamp axis; and a graft assistance apparatus secured to the vascular clamp, the graft assistance apparatus comprising: a securement segment including a securement arm extending therefrom to secure the graft assistance apparatus to the body portion of the vascular clamp, the securement arm defining a passage that is disposed about a securement axis, the passage secured about the body portion of the vascular clamp such that the longitudinal body axis is parallel with the securement axis; and a clamping segment defining a receiver that is disposed about a receiver axis, the graft clamp received in the receiver such that the clamp axis is parallel to the receiver axis, the clamping segment pivotally coupled to the securement segment such that the graft clamp is positioned at a graft angle defined between the occlusion axis of the occlusion portion of the vascular clamp and the clamp axis of the graft clamp.

2. The system according to claim 1, wherein the graft assistance apparatus includes a pivot break that selectively fixes a rotational position of the clamping segment with respect to the securement segment to position the graft clamp at the graft angle.

3. The system according to claim 2, wherein the pivot break comprises a clutch disposed on the securement segment and a prong disposed on the clamping segment, the clutch defining a plurality of notches, the prong selectively receivable in each notch of the plurality of notches to fix the rotational position of the graft clamp at the graft angle.

4. The system according to claim 3, wherein pivot break includes outflow angle indicators that visually indicate the graft angle when the prong is received in a respective notch.

5. The system according to claim 3, wherein the clutch has an arcuate profile.

6. The system according to claim 1, wherein the graft angle is in a range of 30 degrees to 90 degrees.

7. The system according to claim 1, wherein the securement arm extends from the securement segment at an offset angle from a first surface of the securement segment.

8. The system according to claim 7, wherein the offset angle of the securement arm is such that the securement arm secures the securement segment to the body portion of the vascular clamp with the first surface parallel to the occlusion axis of the occlusion portion of the vascular clamp.

9. The system according to claim 1, wherein the vascular clamp is a partial occlusion vascular clamp.

10. The system according to claim 1, wherein the graft clamp is a bulldog vascular clamp.

11. The system according to claim 1 , wherein the graft clamp is configured to fluidly seal an entire diameter of the piece of graft material clamped therein.

12. The system according to claim 1, wherein the graft assistance apparatus is sterilizable.

13. The system according to claim 1, wherein the securement arm forms a snap fit to the body portion of the vascular clamp to secure the securement segment thereto.

14. The system according to claim 1, wherein the securement arm includes a lock knob that locks the position of the graft assistance apparatus on the body portion of the vascular clamp.

15. The system according to claim 1, wherein the graft angle is calibrated to correspond to an outflow graft angle of the piece of graft material when the piece of graft material is grafted to the blood vessel.

16. The system according to claim 1, wherein the graft assistance apparatus is formed of a transparent or a translucent material.

17. A graft assistance apparatus for grafting a piece of graft material to a blood vessel, the graft assistance apparatus comprising: a securement segment including a securement arm extending therefrom, the securement arm defining a securement axis, the securement arm configured to secure the securement segment to a body portion of a vascular clamp having an occlusion portion extending therefrom that defines an occlusion axis; and a clamping segment defining a receiver configured to receive a graft clamp therein, the receiver defining a receiver axis, the clamping segment pivotally coupled to the securement segment and configured to position the graft clamp at a graft angle defined between the receiver axis and the occlusion axis when the graft clamp is received in the clamping segment and the securement segmentis secured to the vascular clamp, the graft angle calibrated to correspond to an outflow graft angle of the piece of graft material when the piece of graft material is grafted to the blood vessel.

18. A surgical kit comprising: a vascular clamp; a graft clamp; and a graft assistance apparatus according to claim 17.

19. A method of implanting a graft, the method comprising: clamping a portion of a blood vessel of a patient with a vascular clamp to partially occlude blood flow through the blood vessel; fixing a securement segment of a graft assistance apparatus to the vascular clamp; clamping a piece of graft material in a graft clamp; fixing the graft clamp to a clamping segment the graft assistance apparatus; and pivoting the clamping segment relative to the securement segment to a graft angle such that the piece of graft material is positioned at an outflow graft angle relative to the partially occluded portion of the blood vessel.

20. The method according to claim 19, wherein clamping the portion of the blood vessel occurs before fixing the securement segment to the graft assistance apparatus.

21. The method according to claim 19, wherein fixing the graft clamp includes inserting the graft clamp into a receiver defined by the clamping segment.

22. The method according to claim 19, further comprising making an incision in the blood vessel at the partially occluded portion of the blood vessel.

23. The method according to claim 19, further comprising grafting the piece of graft material on to the blood vessel at the partially occluded portion of the blood vessel.

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