Mastering Carotid Intervention
What you need to know before performing your next CAS procedure.
To view the figures and tables related to this article, please refer to the print version of our September issue, page 65.
Mastery of carotid interventional techniques can be achieved by all vascular specialists. It is, however, an endeavor that requires embrace, focused dedication, and sufficient ongoing experience. The following is a complete, albeit brief, description of the fundamental technical steps necessary for performing carotid angioplasty-stenting (CAS) in the treatment of stenotic disease of the carotid bifurcation and internal carotid artery (ICA). These technical steps have evolved from our 10-year experience with more than 400 procedures.
Femoral access is the common denominator in all carotid intervention procedures. The target is the infrainguinal common femoral artery (Figure 1). We have found use of the Micropuncture Kit (Cook Inc., Bloomington, IN) to be a superior technique, and we highly recommend it.
Aortic Arch Angiography
Aortic arch angiography is a very important aspect of the procedure because arch anatomy is the single most crucial determinant of technical difficulty with CAS intervention. In most patients, arch angiography can be achieved optimally using a 30º left anterior oblique angle of visualization and 15 to 20 X 30 rate of injection (power injector)—meaning a rate of 15 mL/s to 20 mL/s for a total volume of 30 mL. Arch anatomy has been classified into three categories (A, B, or C) vis-à-vis the anticipated ease or complexity of selective catheterization of the innominate/right common carotid (IA/RCCA) and/or left common carotid artery (LCCA). The degree of difficulty varies with the position of the target vessel origin in relation to the arch apex; selective catheterization and intervention become increasingly difficult (from A to C) with lowering levels (Figure 2). Anatomical variability of branch anatomy is another factor that can significantly impact this intervention; common origin of the IA and LCCA and “bovine” configurations are some of the most frequently encountered.
Selecting the Target Arch Branch (IA/RCCA or LCCA)
Catheter choices are numerous, and every interventionist has his/her own personal preferences. We have found the relatively simple-to-use JB1 or vertebral catheters quite adequate in approximately 90% of our cases. Other choices (among many possibilities) would include the JR4, Cobra, or Vitek (Cook) catheters. Complex shapes and tight angles (eg, Vitek) tend to facilitate engagement but make subsequent advancement more difficult and require stiffer wires. We use an angled 0.035-inch Glidewire (Terumo Medical Corporation, distributed by Boston Scientific Corporation, Natick, MA) with the JB1 and vertebral catheters.
Multiplane Bilateral Angiography
Detailed, multiplane bilateral angiography of the cervical and intracranial vasculature is, of course, a most important aspect in all CAS procedures.
Wiring of the External Carotid Artery
Once a decision to proceed with intervention has been made, and full heparin anticoagulation has been induced, wiring of the external carotid artery (ECA) is the next technical step. This involves placement of a good-support 0.035-inch guidewire (ie, Storq or Wholey type) deep into the ECA and branches. This ECA-anchored wire becomes the rail for advancement of a long interventional sheath (or guiding catheter) into the distal CCA.
An ?access conduit? must now be placed between the puncture access site (femoral artery) and the target common carotid artery. We prefer to use a 6-F or 7-F sheath in most cases; some interventionists would elect to use a guiding catheter (8-F or 9-F). The sheath is advanced to the distal portion of the CCA just short of the bifurcation. Small puffs of radiocontrast material (or road-mapping) can be used to determine adequacy of sheath placement. A 30º to 40º ipsilateral oblique angle often provides the best visualization of the carotid bifurcation and ICA to proceed with intervention. In some cases, optimal imaging of bifurcation anatomy requires lateral, anteroposterior, cranial tilts, or other angles.
Distal Embolic Protection Device
The distal embolic protection device is now advanced across the ICA stenosis, and deployed in the distal (petrous) portion of the cervical ICA. Careful assessment of ICA anatomy must precede deployment of the distal embolic protection device; severe angulations and tight ICA coils are the second most common reason for not performing CAS intervention in our experience (Figure 3).
Predilatation of the ICA Stenosis
Predilatation of the ICA stenosis is strongly favored by most leading CAS investigators; we adhere to such a policy and use it routinely. Several coronary (0.014-inch) and small-vessel (0.018-inch) PTA catheters make good potential choices; balloon diameters of 3 mm to 4 mm in diameter and 20 mm to 40 mm in length are used widely. With embolic protection in place, predilatation has few if any downsides, but it offers significant advantages (vessel sizing and avoidance of snow-plowing when the stent delivery system is advanced across the lesion).
Stent deployment follows predilatation. Nitinol self-expanding devices are preferred by most. Some controversy remains with regard to the extent of vessel coverage and whether the stent should be deployed across the bifurcation and ECA origin. We (and many others) feel strongly that, in the majority of instances, stents should be placed to encompass a 30-mm to 40-mm length of carotid artery, from the distal CCA to the proximal or mid-ICA well past the lesion (Figure 4).
Postdilatation is necessary in most cases, but should be performed only when residual stenosis is >20% after stent placement. A 5-mm or 5.5-mm PTA balloon should be used; larger balloons should only rarely (if ever) be considered.
Cosmetic perfection need not (and should not) be a goal in CAS intervention. This issue is especially significant when dealing with soft/friable carotid lesions that are more likely to embolize. The importance and potential value of limiting manipulations and technical maneuvers are self-evident.
COMMON TECHNICAL CHALLENGES AND PITFALLS
The femoral arteries may not be accessible. In such rare cases, transbrachial CAS intervention is a possible alternative, using the right brachial for the left carotid artery and vice versa. Anatomy of the arch and branches must be assessed critically for such techniques; only those interventionists with significant experience (>100 carotid procedures) should venture into it. Devices and techniques used in aortoiliac crossover and renal artery procedures can be used quite effectively for this purpose (ie, crossover sheaths, renal double curve guiders, etc.).
“C” aortic arches may demand a modified technique. When deep cannulation of the RCCA or LCCA is not possible, one can still attempt CAS through the use of a different strategy that relies on engagement of the origin of the arch branch with an appropriately shaped 8-F or 9-F guiding catheter (H1, AL1, etc.). The intervention can proceed smoothly and in much the same manner from this point on, provided that guiding catheter engagement of the CCA origin is stable (Figure 5).
Dealing with severe angulations and tortuosity of the CCA can be challenging. Attaining stability and positioning of the sheath in the distal CCA in such situations may require keeping the ECA-anchored, 0.035-inch guidewire in place during several steps of the CAS intervention. Use of a 7-F sheath (instead of 6-F) would be helpful because it can better accommodate multiple wires side-by-side.
Tortuosity and marked angulations in the ICA can be a problem. The “buddy wire” technique is used widely for troubleshooting, enabling placement of the distal embolic protection device and stent deployment. Our wire of choice for such maneuvers is the Balance Heavy Weight (Guidant Corporation, Indianapolis, IN). Once again, it is helpful to have a 7-F sheath (or 9-F guiding catheter) to accommodate the various devices all at once.
In the absence of vast experience, CAS intervention should be avoided in the following situations: unfavorable arch anatomy (B+ and C arches), marked angulations/tortuosity of the CCA, heavy circumferential or “coral-reef” calcification of the bifurcation/lesion, and severely angulated ICAs (Figure 6).
Antiplatelet therapy is of paramount importance. Patients are started on clopidogrel 75 mg daily at least 4 days before the planned CAS intervention. At a minimum, the patient must receive a 300-mg loading dose of clopidogrel 2 hours prior to intervention. This therapy is continued for a minimum of 30 days.
The procedures are performed under local anesthesia and are supplemented with little if any sedation. Blood pressure control is also a significant issue. We usually ask patients not to take their antihypertensive medications the morning of the procedure; a starting systolic blood pressure in the 140 mm Hg to 170 mm Hg range is preferred. Pharmacologic interventions to lower and raise blood pressure are often necessary. In the case of hypotension, volume expansion with intravenous saline is the first line of therapy.
Full anticoagulation with intravenous heparin is a routine and important aspect of the CAS procedure. The target activated clotting time is 250 seconds to 300 seconds. Postintervention blood pressure monitoring with an intra-arterial line is performed for a minimum of 2 hours. Patients are allowed to sit up in bed and ambulate a short time afterward.
Frank J. Criado, MD, is Director for the Center of Vascular Intervention and Chief of Vascular Surgery, Union Memorial Hospital–MedStar Health, Baltimore, Maryland. He is a consultant for Cordis and Medtronic AVE. Dr. Criado may be reached at (410) 235-6565; email@example.com.