Methods and systems for treatment of acute ischemic stroke

REFERENCE TO PRIORITY DOCUMENTS

This application claims priority to (1) U.S. Provisional Patent Application Ser. No. 61/919,945, filed Dec. 23, , entitled 'Methods and Systems for Treatment of Acute Ischemic Stroke'; (2) U.S. Provisional Patent Application Ser. No. 62/083,128, filed Nov. 21, , entitled 'Methods and Systems for Treatment of Acute Ischemic Stroke'; (3) U.S. Provisional Patent Application Ser. No. 62/029,799, filed Jul. 28, , entitled 'Intravascular Catheter with Smooth Transitions of Flexibility'; (4) U.S. Provisional Patent Application Ser. No. 62/075,101, filed Nov. 4, , entitled 'Transcarotid Neurovascular Catheter'; (5) U.S. Provisional Patent Application Ser. No. 62/046,112, filed Sep. 4, , entitled 'Methods and Devices for Transcarotid Access'; and (6) U.S. Provisional Patent Application Ser. No. 62/075,169, filed Nov. 4, , entitled 'Methods and Devices for Transcarotid Access.' The disclosures of the provisional patent applications are incorporated by reference in their entirety and priority to the filing dates is claimed.

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BACKGROUND

The present disclosure relates generally to medical methods and devices for the treatment of acute ischemic stroke. More particularly, the present disclosure relates to methods and systems for transcarotid access of the cerebral arterial vasculature and treatment of cerebral occlusions.

Acute ischemic stroke is the sudden blockage of adequate blood flow to a section of the brain, usually caused by thrombus or other emboli lodging or forming in one of the blood vessels supplying the brain. If this blockage is not quickly resolved, the ischemia may lead to permanent neurologic deficit or death. The timeframe for effective treatment of stroke is within 3 hours for intravenous (IV) thrombolytic therapy and 6 hours for site-directed intra-arterial thrombolytic therapy or interventional recanalization of a blocked cerebral artery. Reperfusing the ischemic brain after this time period has no overall benefit to the patient, and may in fact cause harm due to the increased risk of intracranial hemorrhage from fibrinolytic use. Even within this time period, there is strong evidence that the shorter the time period between onset of symptoms and treatment, the better the results. Unfortunately, the ability to recognize symptoms, deliver patients to stroke treatment sites, and finally to treat these patients within this timeframe is rare. Despite treatment advances, stroke remains the third leading cause of death in the United States.

Endovascular treatment of acute stroke is comprised of either the intra-arterial administration of thrombolytic drugs such as recombinent tissue plasminogen activator (rtPA), mechanical removal of the blockage, or a combination of the two. As mentioned above, these interventional treatments must occur within hours of the onset of symptoms. Both intra-arterial (IA) thrombolytic therapy and interventional thrombectomy involve accessing the blocked cerebral artery via endovascular techniques and devices.

Like IV thrombolytic therapy, IA thrombolytic therapy alone has the limitation in that it may take several hours of infusion to effectively dissolve the clot. Mechanical therapies have involved capturing and removing the clot, dissolving the clot, disrupting and suctioning the clot, and/or creating a flow channel through the clot. One of the first mechanical devices developed for stroke treatment is the MERCI Retriever System (Concentric Medical, Redwood City, Calif.). A balloon-tipped guide catheter is used to access the internal carotid artery (ICA) from the femoral artery. A microcatheter is placed through the guide catheter and used to deliver the coil-tipped retriever across the clot and is then pulled back to deploy the retriever around the clot. The microcatheter and retriever are then pulled back, with the goal of pulling the clot, into the balloon guide catheter while the balloon is inflated and a syringe is connected to the balloon guide catheter to aspirate the guide catheter during clot retrieval. This device has had initially positive results as compared to thrombolytic therapy alone.

Other thrombectomy devices utilize expandable cages, baskets, or snares to capture and retrieve clot. Temporary stents, sometimes referred to as stentrievers or revascularization devices, are utilized to remove or retrieve clot as well as restore flow to the vessel. A series of devices using active laser or ultrasound energy to break up the clot have also been utilized. Other active energy devices have been used in conjunction with intra-arterial thrombolytic infusion to accelerate the dissolution of the thrombus. Many of these devices are used in conjunction with aspiration to aid in the removal of the clot and reduce the risk of emboli. Frank suctioning of the clot has also been used with single-lumen catheters and syringes or aspiration pumps, with or without adjunct disruption of the clot. Devices which apply powered fluid vortices in combination with suction have been utilized to improve the efficacy of this method of thrombectomy. Finally, balloons or stents have been used to create a patent lumen through the clot when clot removal or dissolution was not possible.

Disclosed are methods and devices that enable safe, rapid and relatively short transcarotid access to the cerebral and intracranial arteries to treat acute ischemic stroke. The methods and devices include one or more transcarotid access devices, catheters, and thrombectomy devices to remove the occlusion. Methods and devices are also included to provide aspiration and passive flow reversal for the purpose of facilitating removal of the occlusion as well as minimizing distal emboli. The system offers the user a degree of flow control so as to address the specific hemodynamic requirements of the cerebral vasculature. The disclosed methods and devices also include methods and devices to protect the cerebral penumbra during the procedure to minimize injury to brain. In addition, the disclosed methods and devices provide a way to securely close the access site in the carotid artery to avoid the potentially devastating consequences of a transcarotid hematoma.

In one aspect, there is disclosed a system of devices for treating an artery, comprising: an arterial access sheath adapted to introduce an interventional catheter into an artery, the arterial access sheath including a sheath body sized and shaped to be introduced into a common carotid artery via a carotid artery access site, the sheath body defining an internal lumen that provides a passageway for introducing a catheter into the common carotid artery when the first elongated body is positioned in the common carotid artery, wherein the sheath body has a proximal section and a distalmost section that is more flexible than the proximal section, and wherein a ratio of an entire length of the distalmost section to an overall length of the sheath body is one tenth to one half the overall length of the sheath body; an elongated dilator positionable within the internal lumen of the sheath body, wherein the arterial access sheath and the dilator can be collectively introduced into the common carotid artery; and a catheter formed of an elongated catheter body sized and shaped to be introduced via a carotid artery access site into a common carotid artery through the internal lumen of the arterial access sheath, the catheter body sized and shaped to be navigated distally to a intracranial artery through the common carotid artery via the access location in the carotid artery, wherein the catheter body has a length of 40 cm to 70 cm, and wherein the catheter body has a proximal most section and a distal most section wherein the proximal most section is a stiffest portion of the catheter body, and wherein the catheter body has an overall length and a distal most section length such that the distal most section can be positioned in an intracranial artery and at least a portion of the proximal most section is positioned in the common carotid artery during use.

Other features and advantages should be apparent from the following description of various embodiments, which illustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary embodiment of a system of devices for transcarotid access and treatment of acute ischemic stroke showing an arterial access device inserted directly into the carotid artery and a catheter.

FIG. 2 illustrates another embodiment of a system of devices for transcarotid access and treatment of acute ischemic stroke with a balloon-tipped arterial access device and a thrombectomy device.

FIG. 3 illustrates another embodiment of a system of devices for transcarotid access and treatment of acute ischemic stroke with a balloon-tipped guide catheter.

FIG. 4 shows an embodiment of a transcarotid initial access system.

FIG. 5 shows an embodiment of a transcarotid access sheath system.

FIGS. 6-11 show embodiments of a transcarotid arterial access sheath.

FIG. 12 shows an embodiment of an arterial access device which has two occlusion balloons and an opening between the two balloons

FIG. 13 shows an embodiment of a telescoping arterial access device.

FIGS. 14a and 14b show embodiments of an arterial access device with a sheath stopper.

FIG. 15-18 shows an example of an arterial access device comprised of a sheath that has an expandable distal tip.

FIGS. 19-21 show embodiments of dilators.

FIGS. 22-23 show embodiments of catheters.

FIGS. 24A-D show examples of catheters having non-square distal tips or distal edges.

FIGS. 25A and 25B show examples of catheters and tapered dilators in an artery.

FIG. 26 shows an example of a microcatheter with an anchor device.

FIG. 27 shows a guidewire with an anchor device.

FIG. 28 shows a catheter and an arterial access device combined in a single device.

FIGS. 29 and 30 show a catheter having a pair of lumens.

FIGS. 31A-31C show a telescopic catheter and arterial sheath system.

FIGS. 32-35 show examples of systems for treating an artery with active aspiration.

FIGS. 36 and 37 shows cross-sectional views of aspiration pump devices.

FIG. 38 shows an exemplary embodiment of a system that uses venous return to establish passive retrograde flow into the arterial access device.

FIG. 39 shows an exemplary thrombectomy device.

FIG. 40 shows a microcatheter that includes at least two lumens.

FIG. 41-42 illustrates embodiments of a distal perfusion catheter.

FIG. 43-45 illustrate different embodiments of distal perfusion catheters with an occlusion balloon.

FIG. 46 shows a distal region of a perfusion catheter with an expandable device.

FIG. 47 shows a proximal perfusion catheter being deployed distal of the occlusion via the arterial access device or catheter.

FIG. 48A-48D illustrates steps in usage of a distal balloon catheter configured to perfuse distal and/or proximal to the balloon.

FIGS. 49-50 shows an embodiment of an arterial access system which facilitates usage of a vessel closure device.

FIGS. 51-53 show thrombus disruption devices.

FIGS. 54 -57 show tables containing data related to the devices disclosed herein.

DETAILED DESCRIPTION

Interventions in the cerebral or intracranial vasculature often have special access challenges. Most neurovascular interventional procedures use a transfemoral access to the carotid or vertebral artery and thence to the target cerebral or intracranial artery. In recent years, interventional devices such as wires, guide catheters, stents and balloon catheters, have all been scaled down and been made more flexible to better perform in the neurovascular anatomy. Currently, access and treatment catheters to treat stroke range in length from 105 to 135 cm in length, with microcatheters up to 150 cm in length. These catheters access the arterial system from the femoral artery and must navigate the aortic arch and cervical and intracranial arteries to reach the occlusion in the cerebral artery. The access route is long, often tortuous and may contain stenosis plaque material in the aortic arch and carotid and brachiocephalic vessel origins, presenting a risk of embolic complications during the access portion of the procedure. In patients with tortuous anatomy, access to the occlusion may be difficult or impossible with existing catheters and devices. In addition, the cerebral vessels are usually more delicate and prone to perforation than coronary or other peripheral vasculature. Many neurovascular interventional procedures remain either more difficult or impossible because of device access challenges.

One severe drawback to current acute stroke interventions is the amount of time required to restore blood perfusion to the brain, which can be broken down to time required to access to the blocked cerebral artery, and time required to restore flow through the occlusion. Restoration of flow, either through thrombolytic therapy, mechanical thrombectomy, or other means, often takes hours during which time brain tissue is deprived of adequate oxygen. During this period, there is a risk of permanent injury to the brain tissue. In the setting of acute ischemic stroke where 'time is brain,' these extra difficulties have a significant clinical impact.

Another challenge of neurovascular interventions is the risk of cerebral emboli. In order to reach cerebral vessels from a transfemoral access site, catheters must traverse peripheral arteries, the aortic arch, and the carotid arteries. In many patients, there is disease in the form of atherosclerosis in these arteries. Navigating catheters across these arteries may cause fragments to break off and flow to the brain, causing cerebral emboli. Often these emboli lead to procedure-related strokes, but even sub-clinical embolic burdens to the brain have been known to lead to altered mental states.

Once a target site has been reached, there is still a risk of cerebral emboli. During the effort to remove or dissolve clot blockages in the cerebral artery, for example, there is a significant risk of thrombus fragmentation creating embolic particles which can migrate downstream and compromise cerebral perfusion, leading to neurologic events. In carotid artery stenting procedures CAS, embolic protection devices and systems are commonly used to reduce the risk of embolic material from entering the cerebral vasculature. The types of devices include intravascular filters, and reverse flow or static flow systems. Unfortunately, because of the delicate anatomy and access challenges as well as the need for rapid intervention, these embolic protection systems are not used in interventional treatment of acute ischemic stroke.

Some of the current mechanical clot retrieval procedures for stroke treatment use aspiration as a means to reduce the risk of emboli and facilitate the removal of the clot. For example, some clot retrieval procedures include attaching a large syringe to the guide catheter, and then blocking the proximal artery and aspirating the guide catheter during pull back of the clot into the guide. The guide catheter may or may not have an occlusion balloon. However, this step requires a second operator, may require an interruption of aspiration if the syringe needs to be emptied and reattached, and does not control the rate or timing of aspiration. This control may be important in cases where there is some question of patient tolerance to reverse flow. Furthermore, there is no protection against embolic debris during the initial crossing of the clot with the microcatheter and deployment of the retrieval device. Aspiration devices such as the Penumbra System utilize catheters which aspirate at the face of the clot while a separate component is sometimes additionally used to mechanically break up the clot. Aspiration methods and devices can have the potential to more rapidly restore flow and reduce the level of distal emboli, as there is no requirement to cross or disrupt the clot to remove it. However, the efficacy of aspiration with current catheter designs is limited and often requires multiple attempts and/or adjunct mechanical thrombectomy devices, thus diminishing the time and reduced distal emboli benefits.

Disclosed are methods and devices that enable safe, rapid and relatively short and straight transcarotid access to the carotid arteries and cerebral vasculature for the introduction of interventional devices for treating ischemic stroke. Transcarotid access provides a short length and non-tortuous pathway from the vascular access point to the target cerebral vascular treatment site, thereby easing the time and difficulty of the procedure, compared for example to a transfemoral approach. Additionally, this access route reduces the risk of emboli generation from navigation of diseased, angulated, or tortuous aortic arch or carotid artery anatomy. Further, this access route may make some or all aspects of the procedure faster, safer, and more accurate, as described in more detail below. The devices and associated methods include transcarotid access devices, guide catheters, catheters, and guide wires specifically to reach a cerebral target anatomy via a transcarotid access site, and associated stroke treatment devices which have been optimized for delivery through a transcarotid access site also known as a transcervical access site.

Disclosed also are methods and devices to provide aspiration and passive flow reversal either from the access sheath, a guide catheter, or a catheter for the purpose of minimizing distal emboli. Disclosed also are methods and devices that optimize clot aspiration through either transfemoral or transcarotid access approaches. Included in this disclosure are kits of various combinations of these devices to facilitate transcarotid neurovascular interventional procedures.

In another aspect, there is disclosed methods and devices for additionally providing active aspiration as well as passive retrograde flow during the procedure to minimize distal emboli. The system offers the user a degree of blood flow control so as to address the specific hemodynamic requirements of the cerebral vasculature. The system may include a flow controller, which allows the user to control the timing and mode of aspiration.

FIG. 1 shows a system of devices for accessing the common carotid artery (CCA) via a transcarotid approach and for delivering devices to the cerebral vasculature, for example an occlusion 10 in the cerebral artery. The system includes an arterial access device (sometimes referred to herein as an arterial access sheath) having an internal lumen and a port . The arterial access device is sized and shaped to be inserted into the common carotid artery via a transcarotid incision or puncture and deployed into a position that provides access to the cerebral vasculature, for example the common or internal carotid artery. The port provides access to the arterial access device's internal lumen, which is configured for introducing additional devices into the cerebral vasculature via the arterial access device .

FIG. 2 shows an alternate system embodiment, in which the arterial access device has an occlusion balloon that occludes the artery at the position of the sheath distal tip. As shown, the sheath is long enough to reach the distal cervical ICA from the transcarotid access site, but other embodiments may be shorter such that the occlusion balloon positioned in the CCA.

In an embodiment, transcarotid access to the common carotid artery directly with the arterial access device is achieved percutaneously via an incision or puncture in the skin. In an alternate embodiment, the arterial access device accesses the common carotid artery CCA via a direct surgical cut down to the carotid artery. In another embodiment, the arterial access device provides access to the basilar artery BA or posterior cerebral arteries PCA via a cut down incision in the vertebral artery or a percutaneous puncture of the vertebral artery for access to occlusions in the posterior cerebral vasculature such as the posterior cerebral artery or basilar artery. For entry into the common carotid artery, the arterial access device can be inserted into an opening directly in the common carotid artery, the opening being positioned above the patient's clavicle and below a bifurcation location where the patient's common carotid artery bifurcates into an internal carotid artery and external carotid artery. For example, the opening may be located at a distance of around 3 cm to 7 cm below a bifurcation location where the patient's common carotid artery bifurcates into an internal carotid artery and external carotid artery.

The system may also include an intermediate guide catheter. FIG. 3 shows a guide catheter that is inserted through an arterial access sheath via the access device proximal hemostasis valve . The guide catheter includes a proximal adaptor having a proximal port with a hemostasis valve to allow introduction of devices while preventing or minimizing blood loss during the procedure. The guide catheter may also include an occlusion balloon at the distal region.

The systems shown in FIGS. 1, 2 and 3 may also include one or more catheters to provide distal access for additional devices, localized fluid or contrast delivery, or localized aspiration at a location distal of the distal-most end of the arterial access device . A single catheter may be adequate for accessing and treating the occlusion or occlusions. A second, smaller diameter catheter may be inserted through the first catheter or exchanged for the first catheter if more distal access is desired and not possible with the initial catheter. In an embodiment, the catheter is sized and shaped or otherwise configured to be inserted into the internal lumen of the arterial access device via the port . The catheter may use a previously placed guide wire, microcatheter, or other device acting as a guide rail and support mechanism to facilitate placement near the site of the occlusion. The catheter may also utilize a dilator element to facilitate placement through the vasculature over a guidewire. Once the catheter is positioned at or near the target site, the dilator may be removed. The catheter may then be used to apply aspiration to the occlusion. The catheter or dilator may also be used to deliver additional catheters and/or interventional devices to the site of the occlusion.

The disclosed methods and devices also include devices to protect the cerebral penumbra during the procedure to minimize injury to the brain. A distal perfusion device may be used during the procedure to provide perfusion to the brain beyond the site of the occlusion, thereby reducing the injury to the brain from lack of blood. These perfusion devices may also provide a way to reduce the forward blood pressure on the occlusion in the vessel and thus assist in removing the occlusion, for example using either aspiration, a mechanical element, or both.

The system may also include accessory devices such as guidewires and microcatheters, and stroke treatment devices such as stent retrievers, snares, or other thrombectomy devices, which have been optimally configured for reaching a target cerebral or intracranial treatment site via a transcarotid access site. For example, the system may include a thrombectomy device . In addition, the disclosed methods and devices provide for securely closing the access site to the cerebral arteries to avoid the potentially devastating consequences of a transcarotid hematoma. The present disclosure provides additional methods and devices.

Exemplary Embodiments of Arterial Access Devices

Described herein are arterial access devices, also referred to herein as arterial access sheaths or sheath systems. U.S. Patent Publication No. /; and U.S. Provisional Application Ser. No. 62/075,169 entitled 'METHODS AND DEVICES FOR TRANSCAROTID ACCESS' and filed Nov. 4, ; and U.S. patent application Ser. No. 14/537,316 entitled 'METHODS AND DEVICES FOR TRANSCAROTID ACCESS' and filed Nov. 10, which are each incorporated by reference herein, also describe arterial access devices of consideration herein.

As described above, FIGS. 1, 2 and 3 illustrates embodiments of an arterial access sheath that is configured to be directly inserted into the common carotid artery (CCA) without use of a separate introducer sheath. The sheath can be inserted over a guidewire of an initial access system. FIG. 4 shows an embodiment of a transcarotid initial access system 100 or a micro access kit for establishing initial access to a carotid artery for the purpose of enabling introduction of a guide wire into the carotid artery. The access to the carotid artery can occur at an access site located in the neck of a patient such as in the region of the patient's carotid artery. The devices of the transcarotid initial access system 100 are particularly suited for directly accessing the carotid artery through the wall of the common carotid artery. The transcarotid initial access system 100 can include an access needle 120, access guidewire 140, and micropuncture cannula 160. The micropuncture cannula 160 can include a cannula body 162 and an inner dilator 168 slidably positioned within a lumen of the body 162. The inner dilator 168 can have a tapered tip and provide a smooth transition between the cannula and the access guidewire 140. The micropuncture cannula 160 can also include a radiopaque marker 164 near a distal tip of the cannula 160 to help the user visualize the tip location under fluoroscopy. The access guidewire 140 can include guide wire markings 143 to help the user determine where the tip of the guide wire 140 is with respect to the cannula 160. The access needle 120, access guidewire 140, and micropuncture cannula 160 are all adapted to be introduced via a carotid puncture into the carotid artery. The carotid puncture may be accomplished, for example, percutaneously or via a surgical cut down. Embodiments of the initial access system 100 may be adapted towards one or the other method of puncture.

In an alternate embodiment, the arterial access device may be configured for access to the common carotid artery CCA from a femoral artery access site, also without the use of a separate introducer sheath. As above, the access device includes a proximal adaptor with a proximal port with a hemostasis valve and a connection to a flow line (or shunt) which may be connected to means for passive or active reverse flow. The flow line has an internal lumen that communicates with an internal lumen of the arterial access device for shunting blood from the arterial access device. In both transfemoral and transcarotid embodiments, the connection to the flow line is optimized for aspiration of thrombus with flow lumens at least as large as the ID of the arterial access device .

Upon establishment of access to the carotid artery using the initial access system 100, an arterial access sheath of a sheath system such as those described herein may be inserted into the carotid artery at the access site. FIG. 5 shows an embodiment of a transcarotid access sheath system 200 of devices for inserting an access sheath into the carotid artery, for example, over a sheath guidewire of an initial access system. When inserted into the carotid artery, the access sheath system 200 allows for the introduction of at least one interventional device into the carotid artery via a lumen of the access sheath for the purpose of performing an interventional procedure on a region of the vasculature. The transcarotid access sheath system 200 can include an access sheath 220, a sheath dilator 260, and a sheath guidewire 300. The access sheath 220, sheath dilator 260 and sheath guidewire 300 are all adapted to be introduced via a carotid puncture into the carotid artery. The carotid puncture may be accomplished percutaneously or via a surgical cut down. Embodiments of the access sheath system 200 may be adapted towards one or the other method of puncture.

In an embodiment, some or all of the components of transcarotid initial access system 100 and the transcarotid access sheath system 200 may be combined into one transcarotid access system kit such as by combining the components into a single, package, container or a collection of containers that are bundled together.

The arterial access sheath systems described herein can include a distal portion configured to be inserted in the vessel and a proximal portion configured to extend outward from the access site when the distal portion of the arterial access sheath is positioned in the arterial pathway. For example with reference to FIG. 5, the arterial access sheath 220 has an elongated sheath body 222 sized and shaped such that at least a portion of the sheath body 222 is insertable into the artery during a procedure while the proximal portion remains outside the body. The elongated sheath body 222 is the portion of the arterial access sheath 220 that is sized and shaped to be inserted into the artery and wherein at least a portion of the elongated sheath body is actually inserted into the artery during a procedure. A proximal adaptor 224 can be positioned near a proximal end of an elongated sheath body 222 (see also, e.g. port of FIG. 1). The proximal adaptor 224 is configured to remain outside the body when at least a portion of the sheath body 222 is inserted into the artery. The proximal adaptor 224 can have a hemostasis valve 226 that communicates with the internal lumen of the sheath body 222. The hemostasis valve 226 that communicates with the internal lumen of the sheath body 222 allow for the introduction of devices therein while preventing or minimizing blood loss via the internal lumen during the procedure. The hemostasis valve 226 can be a static seal-type passive valve, or an adjustable-opening valve such as a Tuohy-Borst valve 227 or rotating hemostasis valve (RHV) (see FIG. 6). The hemostasis valve may be integral to the proximal adaptor 224, or the access sheath 220 may terminate on the proximal end in a female Luer adaptor to which a separate hemostasis valve component, such as a passive seal valve, a Tuohy-Borst valve or rotating hemostasis valve, may be attached. Further, one or more features can be positioned near the proximal end of the access sheath 220 to aid in securement of the sheath during the procedure. For example, the access sheath 220 may have a suture eyelet 234 or one or more ribs 236 molded into or otherwise attached to the adaptor 224, which would allow the operator to suture tie the sheath hub to the patient.

In an embodiment, the sheath body 222 can have an inner diameter of about 0.087' and an outer diameter of about 0.104', corresponding to a 6 French sheath size. In another embodiment, the sheath body 222 has an inner diameter of about 0.113' and an outer diameter of about 0.136', corresponding to an 8 French sheath size. In an embodiment, the sheath length is between 10 and 12 cm. In another embodiment, the sheath length is between 15 and 30 cm. The diameter and length most suitable to a particular embodiment is dependent on the location of the target site and nature of the devices and flow requirements through the lumen of the access device 200.

In some instances it is desirable to move the proximal port and/or the hemostasis valve away from the distal tip of the arterial access sheath effectively elongating or lengthening the proximal portion (also called a proximal extension herein) that is outside the body while maintaining the length of the insertable distal portion. This allows the user to insert devices into the proximal port of the proximal extension and from there into the lumen of the arterial access device from a point further away from the target site and from the image intensifier used to image the target site fluoroscopically thereby minimizing radiation exposure of the user's hands and also his or her entire body. The proximal extension can be configured such that the length between the proximal port and the arterial access site is between about 30 cm and about 50 cm. The proximal extension can be removable from the arterial access device. An example of a proximal extension design is described in co-pending U.S. Application Publication No. /, filed Aug. 12, , which is incorporated herein by reference. U.S. Pat. No. 8,574,245, U.S. Application Publication No. /, and U.S. Application Publication No. /, which each are also incorporated by reference herein.

FIG. 10 also illustrates an embodiment of an arterial access sheath 220 having a proximal extension portion 805. The proximal extension 805 can have a length suitable to meaningfully reduce the radiation exposure to the user during a transcarotid access procedure. For example, the proximal extension 805 is between about 10 cm and about 25 cm, or between about 15 cm and about 20 cm. Alternately, the proximal extension 805 has a length configured to provide a distance of between about 30 cm and about 60 cm between the hemostasis valve 226 and the distal tip of the sheath body, depending on the insertable length of the access sheath. A connector structure 815 can connect the elongated sheath body 222 to the proximal extension 805. In this embodiment, the connector structure 815 may include a suture eyelet 820 and/or ribs 825 to assist in securing the access sheath 220 to the patient. In an embodiment, the hemostasis valve 226 is a static seal-type passive valve. In an alternate embodiment the hemostasis valve 226 is an adjustable-opening valve such as a Tuohy-Borst valve 227 or rotating hemostasis valve (RHV). Alternately, the proximal extension 805 may terminate on the proximal end in a female Luer adaptor to which a separate hemostasis valve component may be attached, either a passive seal valve, a Tuohy-Borst valve or rotating hemostasis valve (RHV).

The proximal extension and/or proximal adaptor 224 can have a larger inner and outer diameter than the sheath body 222 or the portion of the access sheath configured to be inserted arterially. In instances where the outer diameter of the catheter being inserted into the sheath is close to the inner diameter of the sheath body, the annular space of the lumen that is available for flow is restrictive. Minimizing the sheath body length is thus advantageous to minimize this resistance to flow, such as during flushing of the sheath with saline or contrast solution, or during aspiration or reverse flow out of the sheath. Again with respect to FIG. 10, the sheath body 222 can have an inner diameter of about 0.087' and an outer diameter of about 0.104', corresponding to a 6 French sheath size, and the proximal extension has an inner diameter of about 0.100' to about 0.125' and an outer diameter of about 0.150' to about 0.175'. In another embodiment, the sheath body 222 has an inner diameter of about 0.113' and an outer diameter of about 0.136', corresponding to an 8 French sheath size, and the proximal extension has an inner diameter of about 0.125' and an outer diameter of about 0.175'. In yet another embodiment, the sheath body 222 is stepped with a smaller diameter distal section 605 to further reduce flow restriction, as in FIG. 8.

The proximal extension 905 on the arterial access sheath 220 may be removable. Typically, vessel closure devices requires an arterial access sheath with a maximum distance of about 15 cm between distal tip of the sheath body to the proximal aspect of the hemostasis valve, with sheath body of about 11 cm and the remaining 4 cm comprising the length of the proximal hemostasis valve; thus if the access sheath has a distance of greater than 15 cm it is desirable to remove the proximal extension at the end of the procedure. Again with respect to FIG. 10, the proximal extension 805 can be removable in such a way that after removal, hemostasis is maintained. For example, a hemostasis valve is built into the connector 815 between the sheath body 222 and the proximal extension 805. The hemostasis valve can be opened when the proximal extension 805 is attached to allow fluid communication and insertion of devices, but prevents blood flowing out of the sheath 220 when the proximal extension 805 is removed. After the procedure is completed, the proximal extension 805 can be removed, reducing the distance between the proximal aspect of the hemostasis valve and sheath tip from greater than 15 cm to equal or less than 15 cm and thus allowing a vessel closure device to be used with the access sheath 220 to close the access site.

The arterial access sheath systems described herein are suitable or particularly optimized to provide transcarotid arterial access for reaching various treatment sites from that access site. The working length of the arterial access sheath or sheath/guide catheter system described herein can be considerably shorter than that of long sheaths or sheath guide systems placed, for example, from an access location in the femoral artery. The distance from the femoral artery to the common carotid artery (CCA) is about 60-80 cm moving through the artery. Thus, arterial access devices using a CCA access site may be shorter by at least this amount. Femoral arterial access used to access or deploy a device in the cervical ICA (e.g. the Balloon Guide, Concentric, Inc.) are typically 80-95 cm in length. Femoral arterial access used to access or deploy a device in the petrous ICA (e.g. the Neuron 6F Guide, Penumbra, Inc.) are typically 95-105 cm in length. The shorter lengths of access devices disclosed herein reduces the resistance to flow through the lumen of these devices and increases the rate at which aspiration and/or reverse flow may occur. For example, in an embodiment, the elongated sheath body 222 has a length in the range of about 10 cm to about 12 cm. For access to a same target site from a femoral access site, the access sheaths are typically between 80 cm and 110 cm, or a guide catheter is inserted through an arterial access sheath and advanced to the target site. However, a guide catheter through an access sheath takes up luminal area and thus restricts the size of devices that may be introduced to the target site. Thus, an access sheath that allows interventional devices to reach a target site without a guide catheter has advantages over an access sheath that requires use of a guide catheter to allow interventional devices to the target site.

It should be appreciated that the length and inner diameter of the arterial access sheaths described herein can vary depending on the desired target position of the sheath distal tip. In one embodiment, an access sheath is adapted to be inserted into the common carotid artery (CCA) with the distal tip positioned in the CCA or proximal ICA. In this embodiment, the sheath can have an elongated sheath body 222 having a length in the range of from about 7 cm to about 15 cm, usually being from about 10 cm to about 12 cm. The length considered herein can be the length extending from the proximal adapter 224 to a distal tip of the elongated sheath body 222. For a sheath adapted to be inserted via the common carotid artery (CCA) to a more distal site in the mid or distal internal carotid artery the length of the elongated sheath body 222 can be in the range from about 10 cm to about 30 cm, usually being from about 15 cm to about 25 cm. In another example embodiment, the arterial access device has a length of about 10 cm to about 40 cm. In another embodiment, the length of the arterial access device is about 10.5 cm and a separate guide catheter inserted through the access device has a length of about 32 cm.

In some procedures it may be desirable to incorporate features on the arterial access sheath in order to minimize flow resistance through the insertable portion of the access sheath, for example, as described in U.S. Pat. No. 7,998,104 to Chang and U.S. Pat. No. 8,157,760 to Criado, which are both incorporated by reference herein. For example, FIG. 8 shows such an embodiment of the sheath body 222 having a stepped or tapered configuration such that the sheath body 222 has a reduced diameter distal region 705 (with the reduced diameter being relative to the remainder of the sheath). The distal region 705 of the stepped sheath can be sized for insertion into the carotid artery. The inner diameter of the distal region 705 can be in the range from 0.065 inch to 0.115 inch with the remaining proximal region of the sheath having larger outside and luminal diameters. The inner diameter of the remaining proximal region can typically be in the range from 0.110 inch to 0.135 inch. The larger luminal diameter of the remainder of the sheath body 222 minimizes the overall flow resistance through the sheath 220. In an embodiment, the reduced-diameter distal region 705 has a length of approximately 2 cm to 4 cm. The relatively short length of the reduced-diameter distal region 705 permits this section to be positioned in the common carotid artery CCA via a transcarotid approach with reduced risk that the distal end of the sheath body 222 will contact the bifurcation. In an alternate embodiment, the sheath body is configured to have an insertable portion that is designed to reach as far as the distal ICA. In this embodiment, the reduced-diameter distal section 605 has a length of approximately 10 cm to 15 cm, with a total sheath body length of 15-25 cm. The reduced diameter section permits a reduction in size of the arteriotomy for introducing the sheath into the artery while having a minimal impact in the level of flow resistance. Further, the reduced distal diameter region 705 may be more flexible and thus more conformal to the lumen of the vessel.

In some instances it may be desirable to connect the access sheath to a flow line, for example for the purposes of passive or active aspiration to reduce the risk of distal emboli during the procedure. In an embodiment shown in FIG. 11, the arterial access sheath 220 has a low resistance (large bore) flow line or shunt connected to the access sheath. The low resistance flow line 905 can be connected to an internal lumen of the sheath body 222 via a Y-arm 915 of the connector 815. The flow line 905 may be connected to a lower pressure return site such as a venous return site or a reservoir. The flow line 905 may also be connected to an aspiration source such as a pump or a syringe. As shown in FIG. 11, the flow line 905 can be located distal of the location where devices enter the proximal port 226 of the arterial access sheath 220. In an alternate embodiment, the flow line 905 is attached to the Y-arm of a separately attached Tuohy Borst valve.

The flow line can be connected to an element configured for passive and/or active reverse flow such that blood from the arterial access sheath can be shunted. Connecting the flow line to a lower pressure system, such as a central vein or a reservoir, is an example of passive reverse flow. The reservoir may be positioned on a table near the patient, for a pressure of approximately zero, or positioned below the table to create negative pressure. Examples of devices for active reverse flow are a syringe or other manual aspiration device, or an aspiration pump. The passive or active reverse flow device may be actuated via a stopcock or other flow control switch during critical periods of the procedure, for example when thrombus is being pulled out of the occluded area, into the sheath, and out of the patient. In an embodiment, the flow control switch is integral to the arterial access device. In an alternate embodiment, the flow control switch is a separate component. Because it may be desirable to remove all thrombus from the device with minimal to no chance of material being caught in irregular surfaces or connection surfaces, an embodiment of the access device is constructed such that there is a continuous inner surface with no ledges or crevices at the junction(s) between the lumen of the sheath body, the Y-arm, the flow control switch, the flow line, and the aspiration source.

In some instances, the arterial access sheath is configured to occlude the artery in which it is positioned, for examples in procedures that may create distal emboli. In these cases, occluding the artery stops antegrade blood flow in the artery and thereby reduces the risk of distal emboli that may lead to neurologic symptoms such as TIA or stroke. The arterial access device of FIG. 1 or FIG. 2 may have an occlusion balloon configured to occlude the artery when inflated. In turn, the arterial access device may also include a lumen for balloon inflation. This lumen fluidly connects the balloon, for example, to a second Y-arm on the proximal adaptor. This Y-arm is attached to a tubing which terminates in a one-way stopcock . An inflation device such as a syringe may be attached to the stopcock to inflate the balloon when vascular occlusion is desired. FIG. 9 shows an embodiment of an arterial access sheath 220 with an inflatable balloon 705 on a distal region that is inflated via an inflation line 710 that connects an internal inflation lumen in the sheath body 222 to a stopcock 229, which in turn may be connected to an inflation device. In this embodiment, there is also a Y-arm 715 that may be connected to a passive or active aspiration source to further reduce the risk of distal emboli.

In some configurations, an intermediate guide catheter may be inserted through the arterial access device to provide additional catheter support and potentially distal occlusion. FIG. 3 shows a system with a guide catheter inserted into the CCA through the proximal hemostasis valve of the arterial access device . The guide catheter includes a proximal adaptor having a proximal port with a hemostasis valve to allow introduction of devices while preventing or minimizing blood loss during the procedure. The guide catheter may also include a second Y-arm that communicates with a flow line . Introduction through the separate sheath allows removal of the guide catheter for flushing outside the patient and reinserting, or for exchanging the guide catheter with another guide catheter without removing the introducer sheath , thus maintaining access to the artery via the transcarotid incision. This configuration also allows repositioning of the occlusion balloon during the procedure without disturbing the arterial insertion site. The embodiment of FIG. 11 also allows removal of the arterial access device and then insertion of a vessel closure device through the introducer sheath at the conclusion of the procedure.

In yet another embodiment, as shown in FIG. 12, the arterial access device is a device with two occlusion balloons and and a side opening positioned between the two balloons. The distal occlusion balloon is located at or near the distal end of the arterial access device , and the proximal occlusion balloon is located between the distal end and the proximal end of the working portion of the arterial access device. The distal occlusion balloon is sized and shaped to be placed in the external carotid artery ECA and the proximal occlusion balloon is sized and shaped to be placed in the common carotid artery CCA. Such a dual balloon configuration stops flow into the internal carotid artery ICA from both the CCA and the ECA, which has an effect functionally the same as an occlusion balloon positioned in the ICA without inserting a device into the ICA. This may be advantageous if the ICA were diseased, whereby access may cause emboli to dislodge and create embolic complications, or the access to the ICA were severely tortuous and difficult to achieve, or both. The side opening in the working section of the arterial access device permits a device to be introduced via the arterial access device and inserted into the ICA via the side opening while flow is stopped or reversed, to reduce or eliminate the risk of distal emboli. This device may then be advanced to the location of the cerebral artery occlusion to treat the occlusion.

In yet another embodiment, as shown in FIG. 13 the arterial access device is a multi-part (such as two-part) telescoping system. The access sheath b and/or the distal extension c can be formed of two or more concentric, tubular sections that telescopically slide relative to one another to increase and/or decrease the entire collective length of the movably attached tubular sections. The first part is an access sheath b that is configured to be inserted directly into the CCA. The second part is a distal extension c which is inserted through the proximal end of the introducer sheath b and which extends the reach of the sheath into the ICA. The distal end of the sheath b and the proximal end of the extension c form a lap junction when the extension is fully inserted, such that there is a continuous lumen through the two devices. The lap junction may be variable length, such that there is some variability in the length of the combined telescoping system b. The distal extension c can include a tether which allows placement and retrieval of the distal extension c through the sheath b. In an embodiment, the distal extension c includes an occlusion balloon . In this embodiment the tether include a lumen for inflation of the balloon. This tether can be connected on the proximal end to a balloon inflation device. This configuration provides the advantages of sheath plus guide catheter system shown in FIG. 3, without compromising the luminal area.

The arterial access devices described herein may be configured so that it can be passed through or navigate bends in the artery without kinking. For example, when the access sheath is being introduced through the transcarotid approach, above the clavicle but below the carotid bifurcation, it is desirable that the elongated sheath body 222 be flexible while retaining hoop strength to resist kinking or buckling. This can be especially important in procedures that have limited amount of sheath insertion into the artery and/or where there is a steep angle of insertion as with a transcarotid access in a patient with a deep carotid artery and/or with a short neck. In these instances, there is a tendency for the sheath body tip to be directed towards the back wall of the artery due to the stiffness of the sheath. This causes a risk of injury from insertion of the sheath body itself, or from devices being inserted through the sheath into the arteries, such as guide wires. Alternately, the distal region of the sheath body may be placed in a distal carotid artery which includes one or more bends, such as the petrous ICA. Thus, it is desirable to construct the sheath body 222 such that it can be flexed when inserted in the artery, while not kinking. In an embodiment, the arterial access device can be and is passed through bends of less than or equal to 45 degrees wherein the bends are located within 5 cm, 10 cm, or 15 cm of the arteriotomy measured through the artery.

The working portion of the arterial access sheath, such as the sheath body which enters the artery, can be constructed in two or more layers. An inner liner can be constructed from a low friction polymer such as PTFE (polytetrafluoroethylene) or FEP (fluorinated ethylene propylene) to provide a smooth surface for the advancement of devices through the inner lumen. An outer jacket material can provide mechanical integrity to the inner liner and may be constructed from materials such as Pebax, thermoplastic polyurethane, polyethylene, nylon, or the like. A third layer can be incorporated that can provide reinforcement between the inner liner and the outer jacket. The reinforcement layer can prevent flattening or kinking of the inner lumen of the sheath body as the device navigates through bends in the vasculature. The reinforcement layer can also provide for unimpeded lumens for device access as well as aspiration or reverse flow. In an embodiment, the sheath body 222 is circumferentially reinforced. The reinforcement layer can be made from metal such as stainless steel, Nitinol, Nitinol braid, helical ribbon, helical wire, cut stainless steel, or the like, or stiff polymer such as PEEK. The reinforcement layer can be a structure such as a coil or braid, or tubing that has been laser-cut or machine-cut so as to be flexible. In another embodiment, the reinforcement layer can be a cut hypotube such as a Nitinol hypotube or cut rigid polymer, or the like.

The arterial access sheaths described herein can have a sheath body that varies in flexibility over its length. As described above, a distal-most portion of the arterial access device may be configured to be more flexible than a proximal section of the device. In one embodiment, there is a distal-most section of sheath body 222 that is more flexible than the remainder of the sheath body. The distal section may be at least 10% of the length of the working portion of the catheter wherein the working portion is the portion that is configured to be inserted into an artery. In other embodiments, the distal section is at least 20% or at least 30% of the length of the working portion of the catheter. The variability in flexibility may be achieved in various ways. For example, the outer jacket may change in durometer and/or material at various sections. A lower durometer outer jacket material can be used in a distal section of the sheath compared to other sections of the sheath. Alternately, the wall thickness of the jacket material may be reduced, and/or the density of the reinforcement layer may be varied to increase the flexibility. For example, the pitch of the coil or braid may be stretched out, or the cut pattern in the tubing may be varied to be more flexible. Alternately, the reinforcement structure or the materials may change over the length of the sheath body. For example, the flexural stiffness of the distal-most section can be one third to one tenth the flexural stiffness of the remainder of the sheath body 222. In an embodiment, the distal-most section has a flexural stiffness (E*I) in the range 50 to 300 N-mm2 and the remaining portion of the sheath body 222 has a flexural stiffness in the range 500 to N-mm2 , where E is the elastic modulus and I is the area moment of inertia of the device. For a sheath configured for a CCA access site, the flexible, distal most section comprises a significant portion of the sheath body 222 which may be expressed as a ratio. In an embodiment, the ratio of length of the flexible, distal-most section to the overall length of the sheath body 222 is at least one tenth and at most one half the length of the entire sheath body 222.

In some instances, the arterial access sheath is configured to access a carotid artery bifurcation or proximal internal carotid artery ICA from a CCA access site. As best shown in FIG. 5, the sheath body 222 can have a distal-most section 223 which is about 3 cm to about 4 cm and the overall sheath body 222 is about 10 cm to about 12 cm. In this embodiment, the ratio of length of the flexible, distal-most section to the overall length of the sheath body 222 is about one forth to one half the overall length of the sheath body 222. In another embodiment, there is a transition section 225 between the distal-most flexible section and the proximal section 231, with one or more sections of varying flexibilities between the distal-most section and the remainder of the sheath body. In this embodiment, the distal-most section is about 2 cm to about 4 cm, the transition section is about 1 cm to about 2 cm and the overall sheath body 222 is about 10 cm to about 12 cm, or expressed as a ratio, the distal-most flexible section and the transition section collectively form at least one fourth and at most one half the entire length of the sheath body.

In some instances, the sheath body 222 of the arterial access sheath is configured to be inserted more distally into the internal carotid artery relative to the arterial access location, and possibly into the intracranial section of the internal carotid artery. For example, a distal-most section 223 of the elongated sheath body 222 is about 2.5 cm to about 5 cm and the overall sheath body 222 is about 15 cm to about 30 cm in length. In this embodiment, the ratio of length of the flexible, distal-most section to the overall length of the sheath body is one tenth to one quarter of the entire sheath body 222. In another embodiment, there is a transition section 225 between the distal-most flexible section and the proximal section 231, in which the distal-most section is about 2.5 cm to about 5 cm, the transition section is about 2 cm to 10 cm and the overall sheath body 222 is about 15 cm to about 30 cm. In this embodiment, the distal-most flexible section and the transition section collectively form at least one sixth and at most one half the entire length of the sheath body.

In some instances it is desirable to keep the sheath tip as small as possible during sheath insertion to minimize the diameter of the arterial puncture, but to expand the opening of the sheath after it has been inserted into the vessel. At least one purpose of this feature is to minimize the effect or creation of distal emboli during pull back of an aspiration catheter or other thrombectomy device into the sheath. During a thrombectomy procedure, the thrombus may be 'pulled back' into a distal opening of the sheath on a device that has captured the thrombus. If the distal tip of the sheath is enlarged relative to its initial size, the chance of pieces of the thrombus breaking off and causing emboli is minimized because the larger size of the sheath tip is more likely to accommodate the emboli being drawn into it without being split into multiple pieces. This creates a better clinical outcome for the patient. In an embodiment of the arterial access device, the arterial access device is made of a material and/or constructed such that a tip of the sheath body of the access device can be expanded to a larger diameter once inserted into the artery and positioned in its desired location. In an embodiment, the distal region of the sheath has an ID of about 0.087' can be enlarged to a diameter of about 0.100' to 0.120' although the size may vary.

Examples of expanding distal tip constructions include covered braided tips that can be shortened to expand. Another example of an expanding distal tip construction is an umbrella or similar construction that can open up with mechanical actuation or elastic spring force when unconstrained. Other mechanisms of expandable diameter tubes are well known in the art. One particular embodiment is a sheath made of material that is deformable when expanded using a high pressure balloon.

FIG. 15 shows an example of an arterial access device comprised of a sheath that has an expandable distal tip. As in other embodiments, the sheath has an internal lumen sized and shaped to receive a dilator , which is shown protruding out of the distal end of the sheath . The proximal region of the sheath may be equipped with any of a variety of Y-arms, valves, actuators, etc. FIG. 16 shows an enlarged view of the distal region of the sheath with the dilator protruding outward. In the view of FIG. 16, the distal region of the sheath is unexpanded. The dilator is equipped with an expandable balloon that may be aligned at a desired location along the sheath by sliding the dilator forward or backward relative to the sheath . The dilator may have an inflation lumen and inflation device for inflating the balloon . When the dilator is inserted into the arterial access device sheath , the balloon can be aligned at a desired location of the sheath . When the balloon is inflated, a precise length or region of the sheath is expanded to a precise diameter as a result of the balloon expanding inside the sheath. Once the sheath tip is in its desired location, the balloon is inflated to a pressure that would expand the sheath, as shown in FIG. 17 where a distal region R of the sheath body has been expanded. FIG. 18 shows the sheath with the region R expanded as a result of the balloon being expanded while inside the sheath . In an embodiment, the distal region R is plastically expanded. The sheath body is constructed such that it could stretch to this larger diameter without tearing or breaking. The balloon material may be a non-compliant or semi-compliant material similar or identical to those used in angioplasty balloons, such as nylon. These materials may be inflated to a very high pressure without expanding past the engineered diameter. In a variation, the balloon inflation member is separate from the dilator or on a second dilator, and exchanged for the initial dilator used for sheath insertion, once the sheath is in its desired location. The expanding tip design may be used in place of or in conjunction with an occluding balloon on the sheath to minimize the risk of distal emboli.

The arterial access devices described herein can also be adapted to reduce, minimize or eliminate a risk of injury to the artery caused by the distal-most sheath tip facing and contacting the posterior arterial wall. In some embodiments, the sheath has a structure configured to center the sheath body tip in the lumen of the artery such that the longitudinal axis of the distal region of the sheath body is generally parallel with the longitudinal or center axis of the lumen of the vessel. The sheath alignment feature 508 can be one or more mechanical structures on the sheath body 222 that can be actuated to extend outward from the sheath tip (see FIG. 7). The sheath alignment feature 508 can be an inflatable, enlargeable, extendible bumper, blister, or balloon, located on an outer wall of the arterial access sheath 220. The sheath alignment feature 508 may be increased in size to exert a force on the inner arterial wall to contact and push the elongated body 222 of the arterial access sheath away from the arterial wall. In an embodiment, the sheath body 222 is configured to be inserted into the artery such that a particular edge of the arterial access is against the posterior wall of the artery. In this embodiment, the sheath alignment feature 508 can extend outward from one direction relative to the longitudinal axis of the sheath body 222 to lift or push the sheath tip away from the posterior arterial wall. The alignment feature 508 can be positioned on one side of the sheath body 222 as shown in FIG. 7 or on more than one side of the sheath body 222.

In another embodiment, at least a portion of the sheath body 222 is pre-shaped so that after sheath insertion the tip is more aligned with a long axis of the vessel within which it is inserted, even at a steep sheath insertion angle. In this embodiment, the sheath body 222 is generally straight when the dilator 260 is assembled with the sheath 220 during sheath insertion over the sheath guide wire 300, but once the dilator 260 and guidewire 300 are removed, the distal-most section of the sheath body 222 can assume a curved or angled shape. In an embodiment, the sheath body 222 is shaped such that the distal-most 0.5 cm to 1 cm section is angled from 10 to 30 degrees, as measured from the main axis of the sheath body 220, with a radius of curvature about 0.5'. To retain the curved or angled shape of the sheath body 220 after having been straightened during insertion, the sheath 220 may be heat set in the angled or curved shape during manufacture. Alternately, a reinforcement structure may be constructed out of nitinol and heat-shaped into the curved or angled shape during manufacture. Alternately, an additional spring element may be added to the sheath body 220, for example a strip of spring steel or nitinol, with the correct shape, added to the reinforcement layer of the sheath 220.

In some procedures, it may be desirable to limit the amount of sheath body 222 insertion into the artery, for example in procedures where the target area is very close to the arterial access site. In a stent procedure of the carotid artery bifurcation, for example, the sheath tip should be positioned proximal of the treatment site (relative to the access location) so that it does not interfere with stent deployment or enter the diseased area and possibly cause emboli to get knocked loose. In an embodiment of arterial sheath 220 shown in FIGS. 14A and 14B, a sheath stopper is slideably connected or mounted over the outside of the distal portion of the sheath body. The sheath stopper is shorter than the distal portion of the sheath, effectively shortening the insertable portion of the sheath body 222 by creating a positive stop at a certain length along the sheath body 222. The sheath stopper may be a tube that slidably fits over the sheath body 222 with a length that, when positioned on the sheath body 222, leaves a distal portion of the sheath body exposed. This length can be in the range about 2 cm to about 4 cm. More particularly, the length is about 2.5 cm. The distal end of the sheath stopper may be angled and oriented such that the angle sits flush with the vessel and serves as a stop against the arterial wall when the sheath is