Medical device for voluntarily creating a remedial atrial septal defect

Abstract

A mechanical device for voluntarily creating a remedial atrial septal defect, a sheathed vascular dilator that includes the mechanical device, and methods of voluntarily creating a remedial atrial septal defect in an atrial septum using the mechanical device. The mechanical device includes leading and trailing flanges separated by a circular gap with a circular sharp on the leading flange projecting towards the circular gap.

Description

MEDICAL DEVICE FOR VOLUNTARILY CREATING A REMEDIAL ATRIAL SEPTAL DEFECTBACKGROUND

[0001] Atrial shunts have long been explored as a remedial therapy for various medical conditions.

[0002] In canine models, atrial septal defects were created in a beating heart directly as described by Das et al (Circulation.l993;88(part 1 ): 1754- 1764). The heart was exposed and using purse string sutures in the right atrial wall a simple punch device was introduced into the right atrial cavity. An index finger was passed through a purse string suture in the left atrial appendage to guide the positioning of the tip of the punch at the right spot in the atrial septum. The punch was then used to pierce the atrial septum and the punch opened by an assistant with a screw mechanism. When the atrial septum was seated in the slot for cutting, the punch was screwed back in the original position and a clean hole was punched out. The purse string sutures were tightened to remove the finger and the punch, and the chest repaired, leaving a surgically created atrial septal defect. Such a surgically created atrial septal defect in a beating canine heart was useful for testing transcatheter septal defect occluders.

[0003] The possibility of atrial shunts created through catheter devices in humans is under consideration for treating certain medical conditions. In patients with heart failure with a preserved ejection fraction, where the contractility of the heart may be normal, the etiology is one of increased stiffness of the left ventricle. This leads to heart failure with a preserved ejection fraction (HFpEF). Of the approximately 6 million patients with heart failure in the USA, approximately 50% have HFpEF. Medical therapy is generally the only option for these patients, which therapy is typically complicated by the existence of multiple underlying comorbidities in such patients.

[0004] Hence, a need exists for a medical device capable of perforating the cardiac atrial septum and leaving an atrial septum passage of predetermined and known size, operable for reducing a condition of elevated pressure in the left atrium by shunting a small volume of blood to the right atrium and relieving symptoms of breathlessness and heart failure, without a need for open heart surgery and without a need for a permanent implant.SUMM RY OF THE INVENTION

[0005] A first aspect of the invention is a mechanical device operable for voluntarily creating a remedial atrial septal defect.

[0006] The device comprises an axially elongated cutter operable for incorporation into a vascular dilator that includes at least a leading axial length, a trailing axial length and an intermediate length between the leading axial length and trailing axial length. Each of the leading axial length and trailing axial length have a leading flange and a trailing flange of defined diameter respectively, proximate a transition point to the intermediate length. The intermediate length has a diameter less than the defined diameter of each of the leading flange and the trailing flange so as to provide a cylindrical gap between the leading flange and the trailing flange. The leading flange has a circular sharp defining a knife edge axially projecting towards the cylindrical gap.

[0007] A second aspect of the invention is a sheathed vascular dilator that includes the mechanical device of the first aspect of the invention.

[0008] A third aspect of the invention is a method of voluntarily creating a remedial atrial septal defect in an atrial septum separating a right atrium and a left atrium.

[0009] A first embodiment of the third aspect of the invention includes the steps of (i) creating a transeptal puncture in the atrial septum, (ii) positioning the cutter of the first aspect of the invention within the transeptal puncture until the atrial septum in seated within the cylindrical gap of the cutter, and (iii) withdrawing the cutter to effect cutting of an orifice in the atrial septum with the circular sharp on the cutter.

[0010] A second embodiment of the third aspect of the invention includes the steps of (i) creating a transeptal puncture into the left atrium using a sheathed trans-septal puncture catheter carrying a guidewire passed into the right atrium, (ii) exchanging out the sheath while leaving the guidewire extending through the puncture site and into the left atrium, (iii) loading the sheathed vascular dilator of the second aspect of the invention onto the guidewire,(iv) pushing a tip of the sheathed vascular dilator across the atrial septum a distance to ensure seating of a leading end of the vascular dilator within the left atrium with the cylindrical gap between the leading flange and the trailing flange of the cutter still located in the right atrium,(v) withdrawing the sheath to expose the cylindrical gap, (vi) advancing the vascular dilator until the atrial septum in seated within the cylindrical gap, (vii) withdrawing the vasculardilator to effect cutting of an orifice in the atrial septum with the circular sharp, and (viii) retracting the cutter into the sheath.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a side perspective view of one embodiment of the invention.

[0012] Figure 2 is a side perspective view of the vascular dilator component of the invention depicted in Figure 1.

[0013] Figure 3 is a side perspective view of the punch component of the invention depicted in Figure 1.

[0014] Figure 4 is a cross-sectional view of a human heart with a trans-septal puncture catheter positioned at the inter-atrial septum.

[0015] Figure 5 is a cross-sectional view of the human heart depicted in Figure 4 after trans-septal puncture of the inter-atrial septum with the trans-septal puncture catheter is completed.

[0016] Figure 6 is a cross-sectional view of the human heart depicted in Figure 5 after withdrawal of the trans-septal puncture tipped catheter and leaving a trans-septal guidewire.

[0017] Figure 7 is a cross-sectional view of the human heart depicted in Figure 6 with the invention depicted in Figure 1 passed over the guidewire and inserted into the left atrium over the guidewire.

[0018] Figure 8 is a cross-sectional view of the human heart depicted in Figure 7 after withdrawal of the sheath component of the invention so as to expose the punch component of the invention.

[0019] Figure 9 is a cross-sectional view of the human heart depicted in Figure 8 after the exposed punch component of the invention is pushed into position with the inter-atrial septum surrounding the trans-septal puncture extending into the cutting chamber gap defined by the punch.

[0020] Figure 10 is a cross-sectional view of the human heart depicted in Figure 9 after the punch has been pulled through the trans-septal puncture whereby the circular sharp (knife) on the punch has cut an atrial septal orifice through the inter-atrial septum.

[0021] Figure 11 is a cross-sectional view of the human heart depicted in Figure 10 after withdrawal of the guidewire.

[0022] Figure 12 is an orthogonally shifted cross-sectional view of the human heart depicted in Figure 11 to provide an enhanced view of the atrial septal orifice cut through the inter-atrial septum.DETAILED DESCRIPTION OF A PREFERRED EMBODIMENTNomenclatureCONSTRUCTION

[0023] The invention is a sheathed vascular dilator punch 100 effective for creating a remedial atrial septal defect between the right atrium RA and left atrium LA of a heart H without involving or impact to the right or left ventricles RV and LV or the heart valves (not numbered).

[0024] An atrial shunt or atrial septal orifice ASO 6 to 8 mm in diameter allows the left atrium LA to shunt some blood directly to the right atrium RA - leading to a reduction of the left atrium LA pressure and hence alleviation of symptoms of dyspnea and heart failure.

[0025] Atrial shunts ASO do not have the side effects associated with medical therapy, such as dehydration, kidney injury or electrolyte imbalance. They do not lower the blood pressure or produce orthostatic hypotension. Hence there are attractive benefits.

[0026] The invention is a sheathed vascular dilator punch 100 that includes a cutter or punch 160 incorporated into a commercially available sheathed vascular dilator 140, such as a long 85 cm vascular dilator 140, capable of cutting or punching a definitive hole or orifice in the atrial septum AS without the need for a permanent implant. Since there is no device left behind, there is no potential for device thrombosis, infection, dislodgement, or erosions into the surrounding tissues. If subsequently the atrial septal defect is to be closed, it can be easily closed with standard septal defect occluders that are commercially available.

[0027] Referring to FIG 1 , the component is a punch 160 having a leading threaded length 161, a trailing threaded length 162 and an intermediate length 163. The entire punch 160 can be about 30 mm long. A lumen 169 passes through the axial length of the punch 160 with a diameter sufficient to permit passage of a guidewire GW, typically about 0.04” in diameter.

[0028] The leading and trailing threaded lengths 161 and 162 can be about 10 mm long with ANSI # 4- 40 threads. The threaded leading length 161 threads clockwise facing the right while the threaded trailing length 162 threads clockwise facing the left.

[0029] The leading and trailing threaded lengths 161 and 162 are separated by the intermediate length 163 having an axial length of approximately 9 mm. The leading and trailing threaded lengths 161 and 162 have a leading flange 164a and a trailing flange 164b respectively, at the transition to the intermediate length 163. An intermediate length 163 of about 9 mm is generally suitable. The diameter of the flanges 164 should be selected to fit within the vascular dilator 140. For example, flanges 164 having a diameter of 6 mm will fit within in a 6 mm (18 Fr.) vascular dilator 140 having an outer diameter of 6 mm. The leading flange 164a has a circular sharp (knife edge) 165. The sharp (knife edge) 165 may be serrated for better cutting of tissue. The trailing flange 164b should not be machined.

[0030] The intermediate length 163 can be knurled to permit the punch 160 to be held firmly with an appliance / tool (not shown) when it is threaded onto the vascular dilator 140 and slid into the sheath 120.

[0031] The intermediate length 163 has a smaller diameter than the flanges 164 so as to create a cylindrical cutting chamber gap 168. The leading flange 164a has a circular sharp (knife blade) 165 along the periphery of the inner facing surface. This can be attained by machining a circular groove within the edge.ASSEMBLY

[0032] The punch 160 can be incorporated into a vascular dilator 140 by (i) cutting the vascular dilator 140 about 10 cm from the leading end or tip 141 of the vascular dilator 140, (ii) drilling an appropriately sized axial extending hole into the center of both portions of the vascular dilator 140 from the cut end, and (iii) threading the leading and trailing lengths 161 and 162 of the punch 160 into the drilled holes in each of the leading and trailing lengths 141 and 142 of the vascular dilator 140 respectfully until snug.

[0033] The leading threaded length 161 of the punch 160 can be identified by the circular sharp (knife edge) 165 on the associated leading flange 164a. The lumen 169 through the punch 160 will be in continuity with the central lumen 149 through the vascular dilator 140. Hence, the whole system can be introduced into the body over a guidewire GW.

[0034] The vascular dilator 140 with incorporated punch 160 can be introduced into the lumen 149 of the sheath 120.USE TO PRODUCE CARDIAC ATRIAL SEPTAL DEFECT AND SHUNT

[0035] A sheathed trans-septal puncture catheter PTC carrying a guidewire GW is used with image guidance to create a transeptal puncture (FIGs 4 and 5). The puncture site should be spaced at least 5 mm in each cardinal direction from the edges of the atrial septum AS to prevent adverse impact upon the overall structural integrity of the heart H after removal of tissue surrounding of the puncture site. For instance, to prevent perforation of the walls of the atrium or perforation into the aorta.

[0036] The sheath 120 is exchanged out leaving the guidewire GW extending through the puncture site and into the left atrium LA (FIG 6). The tip of the guidewire GW can be precurved to prevent unintentional perforation of the left atrium LA once unsheathed. The patient should be heparinized at this point.

[0037] The sheathed vascular dilator punch 100 can be loaded onto the guidewire GW outside the body. Using a side-arm, the sheathed vascular dilator punch 100 should be flushed with saline to remove air bubbles.

[0038] The sheathed vascular dilator punch 100 can be introduced into the right femoral vein (not shown) and slowly passed until the tip of the vascular dilator 140 is against the atrial septum AS.

[0039] The tip of the vascular dilator 140 can be pushed across the atrial septum AS a distance to ensure seating of the leading end 141 of the vascular dilator 140 within the left atrium LA (FIG 7) but with the cutting chamber gap 168 of the punch 160 still located in the right atrium RA, at which time the sheath 120 can be withdrawn a sufficient distance, typically about 10 mm, to expose the cutting chamber gap 168 of the punch 160 in the right atrium RA (Fig 8). The vascular dilator 140 can then be slowly advanced while holding the sheath 120 and vascular dilator 140 together until the atrial septum AS is seated within the cutting chamber gap 168 (Fig 9). Imaging can be used to ensure that the atrial septum AS is well seated within the cutting chamber gap 168.

[0040] The sheath 120 can then be slowly advanced until it is at the atrial septum AS.

[0041] The vascular dilator 140 can then be withdrawn with a firm but steady force while holding the sheath 120 in position to cut an orifice into the atrial septum AS with the circular sharp (knife) 165 on the punch 160 and retract the punch 160 back inside the sheath 120.

[0042] The entire length of the vascular dilator 140 can then be withdrawn to the right atrium RA (Fig 10) leaving the guidewire GW in place across the atrial septal orifice ASO cut into the atrial septum AS. Once the atrial septal orifice ASO has been confirmed to be of the appropriate size, the guide wire GW can be removed. (Figs 11 and 12).

[0043] Once sheathed vascular dilator punch 100 is fully removed, firm pressure can be applied to the external puncture site to ensure hemostasis and anticoagulation reversed using a suitable antidote such as Protamine.

Claims

We claim:

1. A mechanical device operable for voluntarily creating a remedial atrial septal defect, the device comprising an axially elongated cutter operable for incorporation into a vascular dilator, the cutter including at least a leading axial length, a trailing axial length and an intermediate length between the leading axial length and trailing axial length, wherein:(a) each of the leading axial length and trailing axial length have a leading flange and a trailing flange of defined diameter respectively, proximate a transition point to the intermediate length,(b) the intermediate length has a diameter less than the defined diameter of each of the leading flange and the trailing flange so as to provide a cylindrical gap between the leading flange and the trailing flange, and(c) the leading flange has a circular sharp defining a knife edge axially projecting towards the cylindrical gap.

2. The mechanical device of claim 1 further comprising an axially extending lumen through the mechanical device configured and arranged to accommodate passage of a guidewire.

3. The mechanical device of claim 1 wherein the leading and trailing lengths are threaded.

4. The mechanical device of claim 3 wherein the leading and trailing lengths are threaded counter to one another.

5. The mechanical device of claim 1 wherein the intermediate length has an axial length of approximately 9 mm.

6. The mechanical device of claim 1 wherein the knife edge is serrated.

7. The mechanical device of claim 1 wherein the intermediate length is knurled.

8. A sheathed vascular dilator that includes the mechanical device of claim 1.

9. A method of voluntarily creating a remedial atrial septal defect in an atrial septum separating a right atrium and a left atrium, comprising the steps of:(a) creating a transeptal puncture in the atrial septum,(b) positioning the cutter of claim 1 within the transeptal puncture until the atrial septum in seated within the cylindrical gap of the cutter, and(c) withdrawing the cutter to effect cutting of an orifice in the atrial septum with the circular sharp on the cutter.

10. A method of voluntarily creating a remedial atrial septal defect in an atrial septum separating a right atrium and a left atrium, comprising the steps of:(a) creating a transeptal puncture into the left atrium using a sheathed trans-septal puncture catheter carrying a guidewire passed into the right atrium,(b) exchanging out the sheath while leaving the guidewire extending through the puncture site and into the left atrium,(c) loading the sheathed vascular dilator of claim 8 onto the guidewire,(d) pushing a tip of the sheathed vascular dilator across the atrial septum a distance to ensure seating of a leading end of the vascular dilator within the left atrium with the cylindrical gap between the leading flange and the trailing flange of the cutter still located in the right atrium,(e) withdrawing the sheath to expose the cylindrical gap,(f) advancing the vascular dilator until the atrial septum in seated within the cylindrical gap,(g) withdrawing the vascular dilator to effect cutting of an orifice in the atrial septum with the circular sharp, and(h) retracting the cutter into the sheath.

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