Arterial disease in humans involves the build up of plaque deposits in arterial walls. The plaque deposits can obstruct blood flow and thus limit the ability of the body to adequately deliver oxygen to tissue. In some instances, blood flow may stop completely. In addition, as flow is diminished, blood clots can form and be released. Plaque rupture may cause loose plaque or a blood clot to migrate down stream to the brain and cause a stroke. Accordingly, it is desirable to treat such plaque deposits (also called lesions) before they cause such problems.
Diagnostic means such as angiography or external ultrasound may be used to determine the extent of arterial disease and may be used to make a recommendation on treatment. Typical treatment may involve a surgical procedure know as carotid endarterectomy whereby plaque is surgically removed, or a less invasive means of treatment called carotid artery stenting. In carotid artery stenting, a nitinol self-expanding cylindrical structure is delivered to the lesion site via an intravascular catheter where the stent is held by the catheter in a collapsed state. A sheath may be used to cover the stent such that, when the sheath is pulled proximally, the stent expands, for example, to press against the inside of the artery. A balloon angioplasty catheter may be used to expand the stent to compress the plaque and restore flow by enlarging the diameter of the artery increasing blood flow at the lesion site. The stent then maintains the enlarged diameter. A nitinol stent (unlike stainless steel stents) has an added benefit that, should the stent be subjected to a collapsing external force, it will restore itself to the previous diameter once the force is removed.
Arterial access for interventional devices such as stent delivery and angioplasty catheters may be achieved through the femoral artery in the groin area. Specifically, access to the carotid arteries may be gained through the femoral artery. The left carotid artery generally extends from the aortic arch to the left side of the neck and into the head. The right carotid artery generally originates as a branch artery from the brachiocephalic trunk which originates at the top of the aortic arch, and extends to the right side of the neck and into the head. Therefore, to reach the carotid artery lesions, catheters must pass from the femoral artery through the descending aorta, into the aortic arch and either directly into the left carotid or through the brachiocephalic artery to the right carotid artery (see FIG. 1).
The treatment of carotid artery disease by stenting is an extension of the prior treatment of coronary artery lesions by stenting. The devices used for access of carotid arteries have their root in those used for coronary angioplasty and stenting. However, the devises used in coronary angioplasty and stenting are not optimal for the more tortuous anatomy of the carotid arteries. Accordingly, efforts have been made to develop devices capable of navigating the anatomy of the carotid arteries.
In coronary angioplasty and stenting, femoral access is typically achieved by use of a needle through the skin to the femoral artery. Blood flowing through the needle indicates that access to the artery has been achieved. This may be referred to as a blood flow indication. One arterial access method, the Seldinger Technique, as applied to accessing the coronary arteries, is as follows:
A guidewire is placed through the needle into the artery and the needle is removed. A dilator and introducer sheath are advanced over the guidewire until the sheath is within the artery. Commonly, the sheath is a 6 French (2 mm inside diameter) sheath, but may be a 5 to 8 French. The dilator and guidewire are then removed. A hemostasis valve, provided at the proximal end of the sheath, may be used to prevent blood loss from the artery.
A guidewire is manipulated through the sheath, through the femoral artery, iliac artery, descending aorta, and aortic arc. A guide catheter with a soft distal tip comprising pre-shaped curve is advanced over the guidewire through the sheath. The guidewire prevents the distal tip from assuming the pre-shaped curve. After advancement of the guide catheter, the guidewire is removed, thus permitting the guide catheter distal end to curve as pre-shaped. The guide catheter is advanced and manipulated until the soft distal tip engages the ostium of the coronary left or right artery. A guidewire is then advanced through the guide catheter and across the lesion. An angioplasty balloon or stent delivery catheter (or other treatment device) is advanced over the guidewire and the stent released in the lesion. Pre or post dilation of the lesion with a balloon catheter may be done over the same guidewire.
A similar technique may be used in accessing the carotid arteries but the curve geometry of the guide catheter and the tortuous pathway through the carotids limits the acceptability/suitability of this approach.
As a result of lower success using a coronary access system, a typical procedure for accessing the carotids now involves the needle access to the femoral artery but places a longer guidewire in the artery before needle removal. The guidewire is advanced to the aortic arch. A diagnostic catheter with a pre-shaped bend in the distal end is advanced over the guidewire until the distal end is near the aortic arch carotid access. The guidewire at this point extends a short distance out the diagnostic catheter distal tip or may be retracted proximally of the curved end of the diagnostic catheter. The diagnostic catheter is manipulated until the distal tip engages the desired artery ostium. The guidewire is then advanced through the carotid artery and the diagnostic catheter is removed. A long dilator having a sheath thereover, is passed over the guidewire into the femoral artery and then advanced into the carotid artery.
An alternative to this procedure is to introduce a long guidewire into the femoral artery, remove the needle, and advance a dilator with a pre-mounted long sheath over the guidewire. The guidewire, dilator, and sheath are then advanced together to a position near the aortic arch. The dilator is removed over the guidewire and a diagnostic catheter is advanced through the sheath over the guidewire until the end of the diagnostic catheter is near the guidewire end (1-2 cm). The diagnostic catheter is advanced and manipulated to gain tip access to the desired ostium and the guidewire is advanced through the diagnostic catheter into the desired carotid artery. The sheath is thus over the diagnostic catheter and guidewire through the carotid artery to a position proximal the lesion of treatment. The guidewire and diagnostic catheter are then removed to allow for introduction of one or more treatment devices.
Although these procedures work for many patients, they are time consuming and involve significant device manipulation and exchanges. Further, these methods of arterial access do not work for all patients. This is typically because of angles at the ostium, anatomical variation, degree of arterial plaque buildup, and/or degree of tortuousity (see FIG. 1). In difficult cases, drag in advancement of the sheath over the diagnostic catheter may cause the diagnostic catheter to prolapse into the aorta, pulling the wire out of the carotid. Similarly a guide catheter may prolapse while attempting to pass a treatment device. This requires a re-start of the procedure for obtaining access. Guide catheters may generally be difficult for use in gaining carotid access due to the size of the aorta, difficulty of engagement into the ostium, and inadequate back up support. Also, because of their size and stiffness, there is a chance that the guide catheter or diagnostic catheter may dislodge plaque in the ostium and cause a stroke from the embolism before a filter can be deployed up stream to capture emboli.
Accordingly, there is a need for an improved systematic approach to carotid artery access.