For Referring Physicians
Newsletter

January 2003

Cerebrovascular Disease

Every 53 seconds, someone in America has a stroke. Stroke mortality reached 160,000 in 1998 and is the nations 3rd leading cause of death. Today it is estimated that there are 4,500,000 stroke survivors, which is a principal cause of long-term disability. Stroke is the number one cause of adult disability in the United States, costing the nation more than $40 billion a year.

There are several reasons that strokes occur. The sudden cessation of blood flow to certain areas of the brain accounts for more than 80% of all strokes. Intracerebral hemorrhage and subarachnoid hemorrhage account for a 10% and 5% stroke rate respectively. Of the strokes related to cessation of blood flow, the majority of these are linked to complications associated with plaque formation at the carotid artery bifurcation.

There are many indications for studying the carotid arteries. An asymptomatic cervical bruit is associated with a 20% incidence of a significant plaque formation at the carotid bifurcation. Episodes of cerebral ischemia (transient ischemic attack, TIA, recently termed brain attack) carry a very ominous set of consequences with the incidence of a stroke following a TIA of approximately 12% in the first year. This is followed by a 6% incidence for each year thereafter, so that within 5 years, at least one third of the patients will have a permanent neurological deficit.

Traditionally, x-ray angiography has been used as the primary method to image the blood vessels. However duplex ultrasound, MR angiography and CT angiography are now being used more and more for the diagnosis of carotid artery disease. Duplex imaging remains the best choice for carotid artery evaluation due to its proven reliability and low cost ($150 -$200) when compared to the other modalities. MR angiography is an excellent study but many times over-estimates the degree of stenosis. Turbulence distal to a carotid plaque creates a flow signal void and the magnitude of the plaque is enhanced, therefore appearing more significant than it really is. CT angiography of the carotid vessels has yet been proven reliable and most likely will not be as cost effective as duplex ultrasonography.

Treatment of asymptomatic carotid artery disease is dependent on the amount of stenosis found at the carotid bifurcation. If an asymptomatic carotid lesion is less than 80%, medical therapy including risk factor modification and drug therapy using platelet antiaggragates should be followed. It must be remembered that while these drugs will reduce the incidence of TIA's as well as reducing stroke risk, they do nothing for slowing or stopping the progression of the carotid plaque. Therefore, once patients are started on the medical regimen, follow-up duplex ultrasound studies are imperative to evaluate for progression of disease.

Studies have shown that moderate plaque in the 50 - 79% range will progress to a critical (>80%) stenosis in 1/4 of patients within a 7-year period. Plaques with stenosis less than 50% showed a 21% rate of progression to the moderate range (50 - 79%) and only a 4% progression to the critical stenosis or occlusion in the same 7-year period. It would therefore seem that patients in the moderate range should be followed quite aggressively. Once progression to greater than 80%, 3/4 of the patients were occluded completely within 7 years and 20% will have a stroke.

Any patient who suffers an episode of transient cerebral ischemia, even if just a single episode, is found to have greater than 60% stenosis or an irregular, ulcerated plaque, should experience significant benefit by surgical intervention. Patients experiencing recurrent transient cerebral attacks who are on antiplatelet therapy, and patients with multiple TIA's regardless of plaque severity would also seem to be good candidates. Patients with good recovery following a significant stroke experience no reduction in stroke risk with aspirin therapy alone. The recurrent risk of stroke can be reduced to 2% per year with surgical intervention when compared to the 9 - 16% per year incidence of recurrent stroke with medical treatment alone.

Carotid endarterectomy was introduced in 1954 as a logical procedure for the removal of atherosclerotic plaque from the carotid bifurcation. Several studies have shown the superiority of surgical treatment over medical management in both the symptomatic and asymptomatic patient.

The North American Symptomatic Carotid Endarterectomy Trial (NASCET) confirmed the effectiveness of carotid endarterectomy in preventing stroke in 659 symptomatic patients who had TIA's or minor strokes with stenosis of the carotid bifurcation of 60 -99%. In addition, long-term outcome was better for surgically treated patients who also had an occluded contralateral carotid artery.

The Asymptomatic Carotid Atherosclerosis Study (ACAS) clinical trial evaluated the combined use of carotid endarterectomy, aspirin therapy and medical risk factor reduction in patients younger than 80 years who had asymptomatic carotid artery stenosis of 60% or more. Based on a five-year projection, the ACAS showed that carotid endarterectomy significantly reduced the relative risk of stroke and death by 53%. The surgical benefit incorporated a low perioperative stroke and death rate of only 2.3%.

Because of the low risk of stroke in asymptomatic patients, we at Apple Hill Vascular Associates follow well established guidelines and only perform carotid endarterectomy when there is well documented progression of the atherosclerotic carotid plaque to 80% or greater.

For patients with blocked carotid arteries, endarterectomy has long been the treatment of choice. But the newest treatment modality - carotid stenting - has researchers trying to figure out which procedure is the best for which patients. So far, the answers are far from clear.

Carotid angioplasty and stenting is currently under investigation in several randomized trials. Current data indicate that the results regarding success and complication rates may be similar to surgery. The largest trial, Carotid Revascularization Endarterectomy versus Stenting Trial (CREST) recently underway is planned for a four-year evaluation time. Many other trials have yet to get underway. Unfortunately, the results of these studies will not reflect the state-of-the-art because new stents and new distal artery protection devices will become available during these studies. Therefore, in clinical practice the decision to perform which type of procedure must be determined on an individual patient basis. Patient with comorbidities considered to be at surgical risk may benefit from carotid angioplasty and stenting while patients with diffuse carotid disease may be a better candidate for surgery.

As always, time will tell!

We at Apple Hill Vascular Associates, Ltd are committed to providing the highest quality of vascular services. Please don't hesitate to call us if there is anything we can do to be of further service to you and your patients. Best wishes for a healthy and prosperous New Year.

Thank you for your continued support!