System and method for guiding catheter in blood vessel

Abstract

Systems and methods for guiding a catheter through a blood vessel including an intracranial vein vascular access are described. Further, systems and methods for treating vasculature conditions are described, including aspiration from the cerebral venous sinus. Generally, the system includes a coaxial combination of a microguidewire, a support catheter having an elliptical section, and an aspiration catheter. Methods of advancing the system through a vascular system, including a venous vascular system having a stenosis section, are also described.

Description

Systems and methods for guiding catheters within blood vessels Technical Field

[0001] Systems and methods for guiding catheters through blood vessels, including intracranial venous access, are described. Furthermore, systems and methods for treating vascular system conditions, including aspiration from cerebral venous sinuses, are described. Typically, the system comprises a coaxial combination of a microguidewire, a support catheter with an elliptical cross-section, and an aspiration catheter. Methods for advancing the system through vascular systems, including venous systems with stenotic segments, are also described. Background Technology

[0002] Cerebral venous thrombosis (CVT) refers to the occlusion of venous pathways within the cranial cavity. These can generally be subdivided into dural venous sinus thrombosis (DVST), cortical venous thrombosis, and deep cerebral vein thrombosis. These conditions often coexist, and their clinical presentations can be very similar and nonspecific. Furthermore, diagnostic imaging features can be subtle.

[0003] DVST is the most common condition. It is most likely to affect women taking birth control pills. However, other risk factors include lifestyle factors, other hormonal factors, medications, anatomical / trauma, and medical conditions. Therefore, more specific risk factors may include smoking, pregnancy, the postpartum period, steroids and hyperthyroidism, prethrombotic blood disorders (including protein S deficiency and polycythemia), COVID-19 and COVID-19 vaccination, local factors (including skull abnormalities, infections (especially mastoid-dural sinus obliterans) and head injuries (especially skull fractures extending to the dural venous sinuses), and systemic diseases (including dehydration, sepsis, malignancies, and connective tissue diseases). DVST can also be caused by idiopathic factors.

[0004] Clinical presentation is variable, ranging from asymptomatic to coma and death. Typically, patients complain of headache, nausea, and vomiting. Neurological deficits are variable. Because DVST obstructs venous outflow from the brain, increased venous pressure and back pressure buildup can lead to brain swelling. Subsequent venous hypertension can cause edema and hemorrhage.

[0005] Once diagnosed, treatment can be challenging. Currently, systemic anticoagulation therapy (such as heparin and warfarin) remains the first-line treatment for dural venous sinus thrombosis. Anticoagulation therapy is usually required even in cases of venous bleeding.

[0006] Interventional treatments include microcatheter thrombolysis or thrombectomy (mechanically removing thrombus material from cerebral veins and sinuses using microcatheters and other endovascular tools). As discussed in more detail below, microcatheter intervention can be challenging with currently available catheter systems. That is, because venous thrombosis is relatively rare (compared to ischemic stroke), there are no catheters specifically designed for venous thrombectomy, and physicians must use catheter systems designed and / or manufactured for cerebral arterial access and thrombectomy.

[0007] However, the details of CVT and cranial venous anatomy have specific characteristics that limit the effectiveness of arterial access / thrombectomy catheters in the venous system.

[0008] Structurally, arterial access catheters are characterized by a maximum outer diameter (OD) of approximately 8F (2.67 mm) (and are typically much smaller). That is, due to the characteristics of ischemic stroke (including the gradual narrowing of distal arteries and blood pressure in the arterial system), the maximum diameter of a larger distal access catheter (DAC) is approximately 8F. Therefore, arterial recanalization surgery typically uses various combinations of biaxial, triaxial, and quadriaxial catheter systems to gradually access more distal regions of the cerebral arteries where thrombosis may have occurred.

[0009] For reference, Table 1 shows a comparison of the legal, metric, and imperial units used in the catheter.

[0010]

[0011]

[0012] The design of arterial access catheters is specific to arterial anatomy, and various features and properties are incorporated into the arterial catheter to enable it to successfully advance into the cranial vascular system for various recanalization procedures.

[0013] In contrast, the cranial venous system has its own specific anatomical features, which present unique challenges for guiding catheters into the venous vascular system. Similarly, DVST differs morphologically from arterial thrombosis.

[0014] For example, as schematically shown in Figures 1 and 1B, the dural sinus has a relatively large diameter (approximately 0.8–1 cm), and DVST can present as substantial damage to this vessel along its length of up to 20 cm. Furthermore, when DVST thrombi form in situ, they typically present as damage along this distance within the dural sinus lumen (rather than complete blockage). The clot can also extend into the cortical vein and / or be present at the junction between the dural sinus and the cortical vein.

[0015] The residual lumen can be as small as 1 mm. Therefore, inserting an arterial access catheter into the dural sinus and aspirating the clot using an 8F (2.67 mm) distal access catheter may only produce a relatively small channel through the clot, which does not significantly reduce the clot burden or alleviate symptoms, as shown in Figures 1C and 1D. That is, the clot Y in the superior sagittal sinus (SSS) can have a diameter of about 0.8–1 cm, and the aspiration catheter AC has a diameter of 2.67 mm, so that when aspiration is applied to clot Y, only a relatively small hole H is produced in clot Y.

[0016] Arachnoid granulations also pose challenges to catheter access and guidance. As shown in Figure 1, arachnoid granulations (AG) exist in the form of bulges that deform the superior sagittal sinus (SSS), and this localized narrowing can severely obstruct catheter advancement.

[0017] Therefore, there is a need for a catheter system specifically designed for and possessing the following functions: effective positioning within the cerebral venous system to achieve DVST treatment, and the ability to guide the unique features of the cerebral venous system. Summary of the Invention

[0018] A catheter system is described for assisting in guiding a catheter through a patient's vascular system in a narrow or tortuous segment of a vessel. The catheter system comprises: an external catheter (OC) having a distal end with a distal internal diameter (ID) and a distal internal circumference (IP); and a supporting catheter (SC) having a distal tip, a proximal end, and a dilation section adjacent to the distal tip, the dilation section having a distal cone, a proximal cone, and an external circumference (OP) substantially corresponding to the distal internal circumference of the external catheter. The dilation section is used to flatten the distal end of the external catheter during catheter insertion.

[0019] In various embodiments:

[0020] • The expansion section has an elliptical cross-section.

[0021] • The external catheter is an aspiration catheter (AC).

[0022] • The dilation section of the support catheter has a long axis and a short axis, with a ratio of 1.5:1.

[0023] • The distal conical portion is 4-12 cm long.

[0024] • The proximal conical portion is 4-12 cm long.

[0025] • The expansion zone is 4-12cm.

[0026] • The expansion segment has a longitudinal axis, and the distal end of the expansion segment can be twisted about the longitudinal axis relative to the proximal end of the expansion segment.

[0027] • The distal tip of the aspiration catheter includes one or more radiopaque dot markers adjacent to the distal tip.

[0028] • Dot markers are at least two dot markers that form a discontinuous band around the circumference of the suction catheter near the distal tip.

[0029] In another embodiment, a catheter system is described for assisting in guiding a catheter through a narrow or tortuous segment of a patient's vascular system. The catheter system comprises: an external catheter (OC) having a distal end with a distal internal diameter (ID) and a distal internal circumference (IP); a support catheter (SC) having a distal tip, a proximal tip, and an elliptical expansion section adjacent to the distal tip, the expansion section having a distal cone, a proximal cone, and an external circumference (OP) substantially corresponding to the distal internal circumference of the external catheter, the expansion section being used to flatten the distal end of the external catheter during catheter insertion; and one or more radiopaque dot markers adjacent to the distal tip of the external catheter.

[0030] In various embodiments, the distal cone is 4-12 cm, the proximal cone is 4-12 cm, and / or the expansion section is 4-12 cm.

[0031] On the other hand, a method for advancing a catheter system as described herein through a patient’s blood vessel with a narrowing segment is described, comprising the steps of: a) introducing the catheter system into the patient at an entry point; b) advancing a support catheter and an external catheter from the entry point toward the narrowing segment; and c) engaging the external catheter on the dilation segment to deform the distal tip of the external catheter into an elliptical shape and pushing the supported distal tip of the external catheter through the narrowing segment.

[0032] The method may also include steps of collecting and cleaning the recovered blood and returning the recovered and cleaned blood back into the patient. Attached Figure Description

[0033] Various objects, features, and advantages of this disclosure will become apparent from the following description of specific embodiments illustrated in the accompanying drawings. The drawings are not necessarily drawn to scale, but rather focus on illustrating the principles of various embodiments of the invention. Similar reference numerals denote similar parts.

[0034] Figures 1, 1A, and 1B are schematic diagrams of cerebral vascular anatomy, showing the venous vascular system and the characteristic DVST thrombus (Figure 1) and the arachnoid granulation (AG) protruding against the superior sagittal sinus (SSS) (Figure 1A). Figure 1B shows the aspiration catheter (AC) being advanced within the SSS.

[0035] Figures 1C and 1D are schematic diagrams illustrating the problem of aspirating large-diameter clots from large blood vessels using small-diameter aspiration catheters.

[0036] Figure 2 is a schematic diagram of a typical microguidewire, microcatheter, and distal access catheter that can be used for arterial recanalization surgery according to the prior art. The diagram illustrates the separation problem between the internal microcatheter / microguidewire and the external catheter, which may be difficult to advance through areas of high tortuosity and / or narrowing in the vascular system.

[0037] Figure 2A is a schematic diagram of the venous vascular system, illustrating the problem of advancing distal access catheters over microcatheters in areas of high tortuosity.

[0038] Figure 3 is a schematic diagram of a venous access system according to one embodiment.

[0039] Figures 3A-3F are perspective views of the catheter system and the guidance process.

[0040] Figures 3G and 3H are perspective views of the elliptical support section of the catheter system and the distal tip of the supporting catheter.

[0041] Figure 4A is a schematic diagram illustrating the problem of guiding a catheter through a narrow section of the vascular system.

[0042] Figure 4B is a schematic diagram showing how an elliptical segment can be guided through a narrow segment of the vascular system.

[0043] Figures 5A and 5B are schematic diagrams illustrating radiopaque markers according to the prior art and the present disclosure. Detailed Implementation

[0044] The accompanying drawings describe a system and method for accessing cerebral venous thrombosis.

[0045] Key structures within the human vascular system (including venous anatomy) make it difficult to guide large-diameter catheters into body parts, including the brain. For the purposes of this specification, the catheter system is described with reference to the venous cerebrovascular system; however, it should be understood that the systems and methods described herein can be used in other parts of the body to treat conditions specific to those sites.

[0046] In a typical procedure, an available arterial-cerebral access catheter is used, with access to the cerebral venous system obtained via the femoral vein. The catheter is advanced into the inferior vena cava, passes through the right atrium, and enters the superior vena cava (SVA). From the SVA, it enters the internal jugular vein (IVA), then the sigmoid sinus, transverse sinus, confluence of sinuses (torcula), and superior sagittal sinus. Alternatively, direct access to the internal jugular vein via percutaneous cervical puncture is also feasible.

[0047] Guiding larger diameter catheters from the typically more flexible neck vessels (i.e., the internal jugular vein) to the contained cerebral vessels (i.e., the sigmoid sinus) is the most challenging. The flexibility and tortuosity of the vessels pose problems for guiding larger diameter catheters.

[0048] Cerebral venous thrombosis (CVT) is a relatively rare form of stroke occurring in the venous system. As schematically shown in Figure 1, a clot Y can form in situ within the cerebral venous system (e.g., the superior sagittal sinus), causing narrowing or occlusion of the veins and restricting blood flow from the brain (dashed lines). These clots can be larger in diameter / length and volume compared to brain clots. During recanalization, guiding the catheter system to the superior sagittal sinus and / or transverse and / or straight sinuses (common sites of dural sinus thrombosis) typically involves advancing from the internal jugular vein, passing through the sigmoid sinus, and entering the superior sagittal sinus. In particular, guidance from the internal jugular vein to the sigmoid sinus can be difficult due to the tortuosity and flexibility of the vessels.

[0049] Furthermore, the relative size of brain conduit systems compared to veins can be problematic, as the relatively small diameter and design of brain conduit systems can present issues, as schematically illustrated in Figures 2 and 2A. Specifically, a gap 17 may exist between the distal edge 18a of the larger conduit and the smaller guiding conduit, making it difficult to traverse areas of high tortuosity and / or areas where the vessel is flexible, as the distal tip may strike sharp corners and potentially become stuck.

[0050] In addition, the presence of arachnoid granules (AG) can cause local narrowing of blood vessels, thus creating a significant guiding obstacle to catheter advancement, as shown in Figures 1A and 4A.

[0051] Arachnoid granulations are rigid, hard projections of the dura mater that bulge into cerebral veins and sinuses. Typically, the diameter of these veins / sinuses is significantly narrowed by these granulations, decreasing by 50% or more. Arachnoid granulations are incompressible; therefore, catheters that could normally fit into cerebral veins / sinuses often become stuck at the granulations, which act as protrusions and prevent further catheter movement. Because granulations cannot be compressed by catheters, if they are present near a site of occlusion, the catheter cannot reach that site.

[0052] Large arachnoid granules are particularly common in the transverse sinus and superior sagittal sinus, which are the most common sites of cerebral venous thrombosis.

[0053] In the first embodiment, as shown in Figures 3 and 3A-3F, the cerebral venous catheter system (CVCS) 10 includes a microguidewire 30, a support catheter (SC) 32, and an aspiration catheter (AC) 34. Each component includes a distal tip 30a, 32a, 34a that can be manipulated, advanced, or pulled back from the proximal end (30b, 32b, 34b).

[0054] As shown in Figure 3B, the microguidewire 30 includes a distal tip 30a and a proximal tip 30b. The microguidewire is typically torsion-compatible and has a deformable or bendable distal tip that allows the tip to be oriented toward a specific blood vessel and then advanced into that vessel.

[0055] As shown in Figure 3B, the support catheter has a distal tip 32a, a proximal end 32b, a distal conical portion 32c, an elliptical segment 32d, a proximal conical portion 32e, and a proximal segment 32f. The support catheter can be advanced on a guidewire.

[0056] Each of the distal conical portion, the elliptical segment, and the proximal conical portion is designed to support a larger-diameter aspiration catheter (AC) or external catheter (OC) that can be advanced over a support catheter and a guidewire, and specifically, to enable the aspiration catheter to be advanced through localized narrowings of blood vessels, such as arachnoid granulations, and / or to prevent the formation of gaps 17 between the aspiration catheter and the support catheter.

[0057] As shown in Figure 4A, localized narrowing sections, such as arachnoid granules, can impede catheter advancement. The combination of distal tapered and elliptical sections allows both the support and aspiration catheters to be advanced through the localized narrowing sections (e.g., arachnoid granules) by transitioning to a flatter (e.g., elliptical) profile. This flatter (e.g., elliptical) profile can more effectively fill the narrowed sections without the distal tips of the support and aspiration catheters getting stuck.

[0058] Referring to Figures 3B-3F, the system and the method of advancing the system through the arachnoid granules are described. For illustrative and clarity purposes, the vessel wall through which the system is advanced is not shown. The arachnoid granules are representatively shown and understood as the narrowing portions as illustrated in Figures 1, 1A, 4A, and 4B. It should also be understood that the advancement of each of the guidewire, support catheter, and aspiration catheter may be sequential, wherein each is advanced in an iterative sequence known to those skilled in the art, prior to reaching the narrowing portion.

[0059] The following description pertains to the sequence of steps for advancing the aspiration catheter through the narrowing, and in particular the structure of the supporting catheter to achieve this. For the purposes of description, it is assumed that the blood vessel has a diameter of approximately 8 mm, the aspiration catheter has an outer diameter of 6 mm (18F), the narrowing extends into the blood vessel to approximately 4 mm, and the guidewire has an outer diameter of 1 mm.

[0060] As shown in Figure 3A, the guidewire 30 is initially advanced through the arachnoid particles. The distal tip of the guidewire can be easily advanced through the narrowing section.

[0061] As shown in Figure 3B, the support catheter 32 is advanced over the guidewire. The distal tip of the support catheter has an outer diameter of approximately 2-3 mm, allowing it to follow the guidewire through arachnoid particles. As shown, in one embodiment, the distal tapered portion 32c transitions from a circular cross-section to an elliptical cross-section within approximately 3 cm. At the proximal end of the distal tapered portion, the support catheter has an elliptical cross-section with a major axis dimension of approximately 6 mm and a minor axis dimension of approximately 3 mm.

[0062] As the distal cone begins to engage with the arachnoid granule, it can also deflect / orient itself relative to the granule, allowing the elliptical segment to fill the unobstructed space shown in Figure 4B and be propelled through the granule. In other words, the distal cone and the elliptical segment can be slightly twisted / rotated to find the optimal position / orientation for movement through the granule.

[0063] As shown in Figure 3C, the aspiration catheter 34 can then be pushed onto the support catheter. The aspiration catheter has a circular cross-section that is larger than the cross-section of the proximal portion of the support catheter.

[0064] As the aspiration catheter is pushed forward, the distal tip 34a engages with the proximal conical portion 32e of the support catheter, which, like the distal tip, transitions from a circular cross-section to an elliptical cross-section. When the distal tip engages with the proximal conical portion, the proximal conical portion stretches / deforms the distal tip 34a, causing the distal tip region of the aspiration catheter to exhibit a potential elliptical shape, as shown in Figures 3D and 3E. The aspiration catheter can then be propelled through the arachnoid granules by advancing the aspiration catheter and support catheter together or by sliding the aspiration catheter over the support catheter.

[0065] The combined system of arachnoid particles can now be pushed / guided to the desired location to initiate surgery, such as aspiration.

[0066] Once in place, as shown in Figures 3F and 3G, the support catheter and guidewire can be retracted, and suction can begin. Upon retraction of the support catheter, the distal tip 34a of the suction catheter will return to a circular shape along its length, but may deform around the arachnoid granules (where the suction catheter rests on the arachnoid granules).

[0067] It is worth noting that aspiration catheters typically have radiopaque markers in the form of a metal band or ring at their distal tip, as shown in Figure 5A. This metal band increases the catheter stiffness at the distal tip and prevents the catheter tip from slipping into an elliptical shape while supporting the catheter. That is, the ring can have stiffness that resists deformation from a circular shape, as indicated by the arrow in Figure 5A. Therefore, to facilitate the ability of the distal tip to deform in elliptical sections, radiopaque markers include discontinuous marking systems, such as multiple metal dots on the outer surface or embedded within the distal tip, as shown in Figure 5B, with sufficiently wide gaps to allow the catheter tip to deform and assume an elliptical shape.

[0068] Support catheters are typically designed such that the outer circumference of the elliptical section corresponds to the inner circumference of the aspiration catheter, with sufficient tolerance to allow the aspiration catheter to slide on the elliptical section. The ratio of the relative lengths between the major and minor axes of the elliptical section is approximately 1.5 to 1, for example, a major axis of 6 mm and a minor axis of 4 mm.

[0069] The lengths of the distal and proximal conical portions are typically about 3 cm, and the total length of the elliptical segment is about 6 cm, although these dimensions can be larger or smaller, as shown in Table 2.

[0070] As shown in Figure 3H, the distal tip of the support catheter is rounded, but in some embodiments, it may be other cross-sectional shapes, including elliptical (dashed line).

[0071] Each of the guidewire, support catheter, and aspiration catheter typically has a total length of approximately 1.1–1.2 m and is originally long enough to be advanced from the femoral vein to the cerebral vein. Shorter catheters may be used if designed for access to the jugular vein or other parts of the vascular system.

[0072] Typically, the length difference between the internal and external catheter components will be in the range of 10-20 cm. That is, the internal component will be about 10-20 cm longer than the external component.

[0073] As described above, the distal conical and elliptical sections of the support catheter provide support for the wider inner diameter of the aspiration catheter. In addition to its ability to advance the aspiration catheter through stenotic areas, the system can also be used to facilitate movement through areas of high vascular curvature and / or flexibility, where there would otherwise be a risk of a gap 17 between the distal tip of the aspiration catheter and the narrower section of the support catheter.

[0074] In other words, if there is a section with a high degree of tortuosity, the suction cannula can be advanced in an elliptical section to prevent the gap from opening.

[0075] Furthermore, it should be noted that elliptical segments typically exhibit greater flexibility along their minor axis than along their major axis. Therefore, in sections with sharp bends, elliptical segments often tend to self-align, aligning their minor axis towards the bend center and providing greater flexibility around sharp corners.

[0076] How to use

[0077] As described above, this system can be used to access the intracranial occlusion site via the patient's venous vascular system. Typically, after the surgeon accesses the patient's vascular system via the femoral vein, the following general procedures are followed:

[0078] a. Advance the internal and external components from the femoral vein to the inferior vena cava.

[0079] b. Advance the internal and external components through the right atrium into the superior vena cava. During steps a and b, the physician will typically use an internal guidewire (usually 0.035 inches) to advance these components sequentially together for guidance.

[0080] c. Access to the internal jugular vein. At this stage, the physician may advance the internal component before the external component, then hold the internal component in place before advancing the external component. During this step, the physician will ensure that the internal and external components are maintained at an appropriate distance to ensure proper engagement of the dilated surfaces.

[0081] d. The procedure will continue through the sigmoid sinus and other structures to reach the desired location for recanalization. As described above, the procedure moves through tortuous or narrowed areas.

[0082] e. Removal of internal components and recanalization surgery, typically performed via aspiration catheter. Once the external catheter is in place within the clot, other adjunctive recanalization techniques (such as thrombolytic agents and / or mechanical agents, such as ultrasonic liquefaction of the clot) can be introduced through the external catheter.

[0083] f. Variations may include triaxial or quadriaxial systems with continuously larger suction cannulas, and are technically adapted accordingly.

[0084] g. Aspiration can be performed manually with a syringe or by a mechanical pump known for the removal of arterial clots.

[0085] CVCS advantages

[0086] The significant advantages of this solution are:

[0087] a. Preloading internal components into the distal access catheter will reduce surgical preparation time.

[0088] b. This system enables the safe placement of larger aspiration catheters, which are specifically designed for the venous system, into larger veins.

[0089] c. Larger diameter catheters allow for the aspiration of clots across the vessel diameter, which is not possible with arterial aspiration catheters.

[0090] d. Importantly, aspirating venous thrombi from the patient can trigger a natural repair / cleaning process to reduce the clot load. If the thrombus load is adequately reduced through thrombectomy, the body's inherent thrombolytic enzymes will dissolve any remaining thrombus residue. Therefore, even if the thrombus cannot be completely removed, minimizing the thrombus load is desirable.

[0091] e. By aspirating the clot or introducing other techniques or agents into the clot to liquefy it, this system enables larger aspiration catheters to be used as catheters for other therapeutic techniques.

[0092] In a variation of this method, the blood removed via the aspiration catheter can be returned to the body after cleaning to remove any blood clot fragments. This step is preferable given the relatively large volume of blood being aspirated due to the larger diameter of the blood vessels and the larger diameter of the catheters.

[0093] The units of measurement used in this manual are consistent with those used in endovascular surgery. That is, both imperial and metric units are used, with length typically expressed in metric units and diameter in imperial units.

[0094] Key features of the cerebral venous duct system (CVCS) are shown in Table 2.

[0095] Table 2 - Typical Dimensions and Properties

[0096]

[0097] Each catheter will preferably include proximal markers and external markers on its body corresponding to opposite end points of the catheter, to help the physician understand the relative position of each catheter to each other during the procedure.

[0098] The corresponding changes in the length of the system designed for internal jugular access can be achieved.

Claims

1. A catheter system for assisting in guiding a catheter through a blood vessel in a patient's vascular system having a narrow or tortuous segment, the catheter system comprising: An external catheter (OC) having a distal end having a distal inner diameter (ID) and a distal inner circumference (IP); A support catheter (SC) having a distal tip, a proximal end, and a dilation section adjacent to the distal tip, the dilation section having a distal taper, a proximal taper, and an outer circumference (OP) substantially corresponding to the distal inner circumference (IP) of the external catheter (OC), the dilation section being used to flatten the distal end of the external catheter (OC) during catheter insertion.

2. The catheter system according to claim 1, wherein, The expansion section has an elliptical cross-section.

3. The catheter system according to claim 1, wherein, The external catheter (OC) is a suction catheter (AC).

4. The catheter system of claim 1 further includes a microguidewire configured to move within the support catheter (SC).

5. The catheter system according to claim 2, wherein, The expansion section of the support catheter (SC) has a long axis and a short axis, and the ratio of the long axis to the short axis is 1.5:

1.

6. The catheter system according to claim 1, wherein, The distal conical portion is 4-12 cm long.

7. The catheter system according to claim 1, wherein, The proximal conical portion is 4-12 cm long.

8. The catheter system according to claim 1, wherein, The expansion section is 4-12cm.

9. The catheter system according to claim 1, wherein, The expansion section has a longitudinal axis, and the distal end of the expansion section is capable of twisting about the longitudinal axis relative to the proximal end of the expansion section.

10. The system of claim 1, further comprising one or more radiopaque dot markers adjacent to the distal tip.

11. The system according to claim 9, wherein, The dot markers are at least two dot markers that form a discontinuous band-like distribution around the circumference of the suction catheter near the distal tip.

12. A catheter system for assisting in guiding a catheter through a blood vessel in a patient's vascular system having a narrow or tortuous segment, the catheter system comprising: An external catheter (OC) having a distal end having a distal inner diameter (ID) and a distal inner circumference (IP); A support catheter (SC) having a distal tip, a proximal end, and an elliptical expansion section adjacent to the distal tip, the expansion section having a distal taper, a proximal taper, and an outer circumference (OP) substantially corresponding to the distal inner circumference (IP) of the external catheter, the expansion section being used to flatten the distal end of the external catheter (OC) during catheter insertion; And one or more radiopaque dot markers, the one or more radiopaque dot markers being adjacent to the distal tip.

13. The catheter system according to claim 12, wherein, The distal conical portion is 4-12 cm long.

14. The catheter system of claim 12, wherein, The proximal conical portion is 4-12 cm long.

15. The catheter system according to claim 12, wherein, The expansion section is 4-12cm.

16. A method of advancing a catheter system through a patient's blood vessel with a narrowed segment, using the catheter system according to claim 2, the method comprising the steps of: a) Introduce the catheter system into the patient at the entry point; b) Advance the support catheter (SC) and external catheter (OC) from the entry point toward the narrowing section; c) Engage the external catheter (OC) onto the expansion section to deform the distal tip of the external catheter (OC) into an elliptical shape and push the supported distal tip of the external catheter (OC) through the narrowing section.

17. The method of claim 16, further comprising the steps of collecting and cleaning the recovered blood and returning the recovered and cleaned blood back into the patient.

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