Carotid stenting offers new interventional practice option

As carotid artery stenting becomes an accepted tool for stroke prevention in appropriate patients, interventional radiologists and neuroradiologists are determining where this procedure fits into their practice. Some have already developed an active carotid artery stenting practice, but others are looking for resources to help them begin to offer this service. Consideration of many elements is required to offer a high-quality service.

Even though cardiologists and vascular surgery practitioners have skills and practices that may lend themselves to carotid artery stenting (CAS), IRs and interventional neuroradiologists could potentially offer high-quality service to patients and referring physicians. Their background with cervical and cerebral diagnosis and interventions should allow them to compete effectively in this arena.

Most interventional radiologists have significant training in catheter and guidewire skills. Many also have specific skills in catheterizing brachiocephalic vessels and extensive experience in treating atherosclerotic disease with balloons and stents, as well as in related procedures such as cerebral artery angioplasty and transcatheter intracranial thrombolysis. These basic IR skills will transfer to CAS. Depending on specific training and experience, additional work to develop skills in maneuvering catheters, wires, and sheaths into diseased aortic arches and brachiocephalic vessels may be needed. Absolute comfort with catheterizing these vessels, particularly when diseased, is necessary before therapeutic interventions can be contemplated. Interventionalists entering this field may develop familiarity with the use of 0.014-inch wires and rapid exchange catheters and balloons.

Also essential are absolute familiarity with brachiocephalic and cerebral anatomy, the ability to recognize anatomic variants and pathology other than carotid bifurcation stenosis, and skill at performing and interpreting diagnostic tests to assess neurovascular disease, including Doppler ultrasound and MR-, CT-, and catheter-based angiography. It is necessary to understand cerebral artery anatomy and functional mapping of the brain in order to appreciate the clinical significance of complications of CAS and what steps to take should complications occur.

There is an art to stenting areas of stenosis in vessels. Skill in delivering stents includes not only the actual deployment of the stent, but also knowledge and understanding of which lesions will be best suited for treatment with stents. Necessary skills and knowledge include the use of balloons, maneuvering of wires through tortuous and stenotic vessels, and use of 0.014-inch-based systems, rapid exchange technology, and embolic protection devices (EPDs). These skills are obtained through both training and clinical and technical experience.

Interventional radiologists must have skills and training in neurologic assessment and evaluation of patients. Medical, carotid endarterectomy, and carotid stent trials outline the risks and benefits of various carotid disease treatment options. The physician seeing patients in consultation for carotid disease must be able to take a neurologic history to determine whether the patient is symptomatic, and if so, what vascular distribution accounts for the symptoms. Assessment of the patient's neurologic status before, during, and after the procedure is necessary to determine whether neurologic changes are occurring during or after the procedure that require immediate treatment to prevent stroke. Rapid treatment of complications of the procedure includes management of bradycardia and hypotension, acute stroke, angina, groin complications, and fluid requirements.

To assure they are able to deliver the high-quality care required for effective evaluation and management of CAS patients, interventional radiologists should determine what areas require further knowledge and training. Device-specific training is also a prerequisite for successful treatment of carotid stenosis with CAS. Depending on your skill level, you may need only a simple lesson with the sales rep a few minutes before the procedure, or more formal didactic training, observation of cases, and/or use of simulators.

Didactic training can be Web-based, in person, or a combination. The FDA has mandated formal training on approved devices. As more devices are approved, specific training with each EPD and stent will likely be required prior to use. Depending upon previous experience with CAS, proctoring may be necessary for a certain number of cases as well. This may be FDA-mandated, Centers for Medicare and Medicaid Services-mandated, and/or locally mandated by credentialing criteria. Local product representatives should be resources for obtaining specific information on FDA-mandated training.

Familiarity with equipment that may be necessary for the procedure is essential, along with access to tools needed to negotiate difficult anatomy or to successfully complete the procedure despite technical challenges.

Training can also include neurologic evaluations to fine-tune assessment of subtle changes in neurologic exams and ensure ability to respond should the patient experience a neurologic event during or after the procedure.

The physician must be experienced or familiar with drugs that may be necessary to safely complete the procedure, including preprocedure medications such as aspirin and clopidogrel; intraprocedure drugs such as conscious sedation agents, heparin, atropine, pressors, and vasodilators; and postprocedure drugs.

In many practices, the interventionalist is expected to oversee the patient during the hospitalization. This may require management of hypertension, hypotension, diabetes, renal insufficiency, and cardiac arrhythmias. Management of these comorbid conditions may involve consultion with the appropriate specialists, but the interventionalist is often responsible for asking for these consultations and for managing the overall care of the patient. This can include following the patient in the ICU (or regular hospital postprocedure care area) and discharging the patient, arranging for follow-up, writing prescriptions for drugs, and communicating with the referring doctor and/or primary-care doctor directly.

CLINICAL PRACTICE

Building a CAS practice requires a referral stream. CAS has a longer learning curve than some IR procedures, and an interventionalist, even one with an active vascular practice treating other peripheral vessels, probably needs to perform this procedure on a regular basis to achieve the best outcomes. The referral base will vary, depending upon who manages stroke patients and who else is offering therapeutic services for carotid disease. The IR must develop a quality service and then market this service to referring physicians, emphasizing his or her abilities and knowledge, not only of the CAS procedure, but also of the underlying disease, appropriate workup, and all treatment options.

The importance of a clinical office practice cannot be overstated. For referring physicians to see the IR as a consultant, the IR needs to be able to see the patient, direct the patient evaluation, consider all treatment options, and make recommendations to the patient and referring physician. The IR must be able to follow the patient, assess for long-term outcomes, monitor for further manifestations of the underlying disease, and treat the underlying disease. This can be done only with a clinical office practice.

Screening patients in a peripheral vascular clinic may lead to the discovery of significant disease in patients at risk for carotid stenosis and stroke. Screening includes taking a neurologic history, listening to the carotids with a stethoscope, and sometimes instigating noninvasive testing. Discovery of asymptomatic carotid stenosis that is below the threshold for treatment at the time of diagnosis merits appropriate lifestyle management and medical therapy for vascular disease, as well as follow-up of this patient with serial noninvasive testing, since these stenoses tend to progress. These steps are part of the general management of peripheral vascular disease, which is a systemic condition and should be treated as such.

In general, referrals come from primary-care physicians who find a bruit on physical examination or see patients for transient ischemic attacks. Neurologists, cardiologists, vascular surgeons, and emergency room physicians are all potential sources of referrals. Diagnostic radiology partners or IRs themselves may be able to gain referrals from noninvasive diagnostic imaging studies of carotids including Doppler ultrasound, CTA, and MRA. Screening programs offered in the community may identify patients with carotid stenosis at risk for stroke, and these can also be a source of referrals.

Giving talks to physician groups during grand rounds or section meetings can provide an introduction to these physicians and educate them about services available. News stories may attract the attention of patients or families, particularly those who have been told they are not good candidates for surgery.

FACILITY CRITERIA

Medicare has issued criteria for facilities that must be met for CMS reimbursement of CAS.¹ As of 2005, Medicare covers CAS only when performed in in-patient facilities. Documentation of the facility's abilities must be submitted to CMS prior to performance of CAS procedures, and the facility must be listed by CMS as an approved provider site. The facility must meet requirements in several areas:

- Physical facility and personnel. The facility requirements cover the interventional suite equipment and personnel, pre- and postprocedure units and staff, intensive care units and staff, neurology staff, and possibly vascular surgery or neurosurgery should bailout be required. In general, the appropriate personnel must be in place to assure quality patient care. Staff must have had training specific to the CAS procedure and potential complications. The appropriate personnel should be educated in pre- and postprocedure care, including development of pathways for care in the hospital to help ensure continuity of high-quality patient care. Development of standard preprocedure and postprocedure orders in conjunction with pharmacy and nursing will help in preventing and monitoring complications. Some personnel may be familiar with carotid surgeries but will need additional training regarding CAS. This may require provision of in-service training and help in writing policy and procedure for CAS. The interventionalist must become the information source for nurses, hospital administration, and technologists, as well as referring physicians.

- Interventional suite. Imaging equipment capable of providing the high-quality images required for CAS must be available. While CMS does not cite specific requirements for imaging, outcomes will depend on accurate imaging. Digital subtraction angiography is considered an absolute requirement for successful CAS by most interventional radiologists. The ability to perform DSA imaging of intracranial vessels both before and after CAS placement is also essential.

Radiologic technologists and nurses must be trained to become familiar with the procedure and the necessary catheters, guidewires, and other equipment as well as drugs, neurologic assessments, and potential complications. The staff needs recent and frequently updated in-service training in the carotid stent and protection device. Training needs depend on the volume of cases being performed and the number of staff performing the procedure. At least initially, it is best to keep a small core group of staff dedicated to CAS to allow them to become adept at the procedure.

The lab must be stocked with a wide variety of catheters, guidewires, sheaths, femoral closure devices, and drugs to enable response to a multitude of challenges that may arise during a procedure.

- Critical care units. Access is required to appropriately staffed and equipped critical care units. Patients undergoing CAS are often fragile, and many have one or more underlying medical comorbidities. Patients may develop prolonged hypotension requiring pressor infusions and monitoring, cardiac problems, groin complications, and neurologic complications. CCUs should be familiar with management of all of these potential complications. Education of the nursing staff will help assure the best patient care.

- Quality assurance. Facilities are required to monitor outcomes of CAS procedures in order to qualify for CMS reimbursement. While national databases are being developed, they are not available as of this writing. The local facility is responsible for instituting a method for following outcomes and reporting those as required to CMS. The facility is also required to have a formal credentialing process in place for CAS in order to qualify for Medicare reimbursement. This can be relatively easy to establish, but it may be difficult if political issues lead to significant disagreement. Documents are available that can help hospitals write credentials criteria.^2-4

- Neurologic consultation. The need for neurologic consultation may vary, depending on the patient and the interventional radiologist. Neurologic evaluation will be needed at some points, however, so access to neurology is necessary. This can be obtained through neurologists, neurosurgeons, and/or ancillary personnel trained in neurologic assessments. Neuro assessment (typically with the National

Institutes of Health Stroke Scale or other defined stroke scale) is important to document the patient's condition before and after the procedure. It should be performed by a healthcare professional who is not the CAS operator.

- Follow-up. Patients who have undergone CAS are at risk for late complications such as restenosis or thrombosis at the stent site. They are also at risk for development of disease in the other carotid or in other vessels, and they require follow-up to manage the atherosclerotic disease. Most patients who have undergone CAS are continued on antiplatelet therapy. This typically includes use of clopidogrel (or ticlopidine) for 30 to 90 days, then aspirin indefinitely. The regimen may also include statins for lipid management, as well as other routine cardiovascular risk reduction methods. If patients have been hypotensive immediately following CAS, their antihypertensive drugs may require short-term management in the immediate postdischarge period.

Patients are typically seen in the office a week after the procedure and then at four to six weeks. At that time, a history and physical exam specific to the CAS procedure are done. The follow-up exam includes checking the groin, performing a baseline Doppler of the affected carotid, and listening for a bruit. A gross neurologic exam is performed. If the patient is recovering well, a follow-up visit, including carotid duplex exam, is scheduled, typically on an annual basis.

- Research personnel. The population of patients covered by Medicare is narrow. Medicare covers patients who are symptomatic with > 70% stenosis and are at high risk for carotid endarterectomy. Only small numbers of patients will qualify for Medicare coverage for this procedure outside of clinical trials. To develop an active CAS practice, therefore, it may be helpful to participate in these clinical trials. This will increase the number of treatable patients and can help establish referral patterns by expanding the pool of patients who would otherwise not qualify for treatment. Participation in clinical research trials requires access to research personnel (clinical research coordinator) and an institutional review board. Ongoing CAS trials will include postmarket surveillance trials for each CAS system, as mandated by FDA, and these will involve a variety of centers and levels of operator experience. There are also ongoing randomized trials for low-risk patients, including the NIH-sponsored CREST and the Abbott-sponsored ACT I low-moderate risk trial. Some of these trials are likely still recruiting investigators.

The development of a carotid stent practice is an extension of the general vascular practice, but with very specific new skills and cognitive background required. Laying the proper foundation with referring physicians, imaging colleagues, hospital nurses, technicians, and hospital administration, will help lead to a rewarding CAS practice and avoid the pitfalls awaiting the unprepared.

References

1. http://www.cms.hhs.gov/med/viewdraftdecisionmemo.asp?id=128

2. Conners JJ, Sacks D, Furlan AJ, et al. Training, competency, and credentialing standards for diagnostic cervicocerebral angiography, carotid stenting, and cerebrovascular intervention. J Vasc Interv Radiol 2004;15:1347-1356.

3. Barr JD, Conners JJ, Sacks D, et al. Quality improvement guidelines for the performance of cervical carotid angioplasty and stent placement. J Vasc Interv Radiol 2003;14:1079-1093.

4. Creager MA, Goldstone J, Hirshfeld JW Jr, et al. ACC/ACP/SCAI/SVMB/SVS clinical competence statement on vascular medicine and catheter-based peripheral vascular interventions. JACC 2004;44:941-957.

Dr. Krol is director of interventional radiology at CorVasc MDs, St. Vincent Hospital, in Indianapolis. Dr. Raabe is director of radiology at Sacred Heart Medical Center in Spokane. Dr. Murphy is director of the Vascular Disease Research Center in Providence, and Dr. Wholey is chairman of the Pittsburgh Vascular Institute at the University of Pittsburgh Medical Center Shadyside.

Dr. Wholey is a consultant for Cordis, Guidant, Boston Scientific, Edwards Life Science, and Medrad and a stock shareholder of Setagon, Atache and PST.