Revascularization of Asymptomatic High-Grade Carotid Stenosis Is Still Indicated in Some Cases
A 61 year-old man with an asymptomatic ICA stenosis (ACS) greater than 80%.
(1) Should prophylactic carotid revascularization be considered in this patient to reduce future stroke risk?
(2) Should tests like transcranial Ultrasound for microemboli detection or vascular reserve assessment be used to stratify ACS patients at high risk for stroke who would be more likely to benefit from revascularization?
(3) Is revascularization more beneficial than modern best medical therapy (antiplatelets, ACE inhibitors, and statins) in this patient?
Revascularization of asymptomatic high-grade carotid stenosis is still indicated despite contemporary stroke prevention medical therapy.
Up to 20% of ischemic stroke is caused by carotid artery disease. Robust evidence shows that operating for symptomatic carotid stenosis prevents stroke if performed early after the ischemic event, but the majority of strokes due to carotid stenosis are not preceded by minor stroke or transient ischemic attack. One approach to preventing stroke in this group of patients is to operate before symptoms occur, that is, on asymptomatic carotid stenosis (ACS).
Results from 2 large well-conducted randomized controlled trials have shown that carotid endarterectomy (CEA) for ACS reduces the risk of further stroke.1,2 Despite highly significant results, the use of this preventive therapy has been questioned for 2 main reasons. First, the risk of recurrent stroke in the trials was low, as would be expected for ACS, at approximately 2% per annum. This resulted in a large number needed to treat; it was estimated that 40 operations were needed to prevent 1 disabling or fatal stroke after 5 years.3 After the trials, there was controversy as to whether this treatment benefit was worthwhile for the individual patient and also whether it was value for the money considering the many competing demands on health services. The controversy has intensified with more recent data suggesting stroke risk in medically treated patients with ACS is now significantly lower than that reported in the randomized clinical trials.4 It has been suggested that this negates any benefit of surgery or could even make surgery dangerous.
Confirming this will require trials comparing CEA with current best medical therapy such as statins and rigorous control of blood pressure. Trials are currently evaluating CEA against stenting for ACS and it is important that these include a medical arm so that we can derive this information. However, such data will not be available for many years. What should the practicing clinician do in the interim?
ACS presents to many different clinical specialties, including neurology and stroke, cardiology, and vascular surgery. It is important each institution has a preagreed policy. After reviewing the data in conjunction with our vascular surgeons, we concluded that operating on all ACSs was not worthwhile. However, subgroup analysis from the randomized trials has suggested there is a greater benefit in men aged ≤74 years.3 Therefore, in men <75 years, we discuss the potential benefits and risks of operation, emphasizing that this is only 1 part of a treatment package that includes intensive treatment of cardiovascular risk factors and lifestyle modification. In our experience, approximately a half of such patients opt to proceed with CEA. In older men and women with ACS, we would suggest medical treatment alone.
The reason treatment benefits are so small in ACS is because we are operating on a group of patients whose risk of stroke, if left untreated, is low. An attractive concept is to identify a subgroup who are at higher risk, who may particularly benefit from the intervention, and conversely spare those at lower stroke risk from the risks of CEA. A number of markers of increased risk have been suggested, including the presence of CT infarction, degree of stenosis, plaque morphology on ultrasound or MRI, impaired cerebral hemodynamics, and asymptomatic embolization detected by transcranial Doppler ultrasound. Prospective studies have suggested plaque morphology and the presence of emboli are most promising.5,6 The recent Asymptomatic Carotid Emboli Study (ACES) found asymptomatic embolization, detected on either of 2 1-hour baseline recordings, was a highly significant predictor of risk over the subsequent 2 years.5 A meta-analysis of ACES with previous studies confirmed this finding.5 Transcranial Doppler ultrasound is a simple, noninvasive technique. However, there is a need for reliable automated systems, which can be easily used in clinical practice, for identification of the embolic signals; such systems have been developed for the larger emboli seen in symptomatic disease, but further work is required to confirm they can reliably identify the less intense signals seen in patients with ACS. Until these are available, it is likely to remain primarily a research technique.
So what would I do in this 61-year-old man? I would explain to him the small potential benefits from CEA, counsel him about the risks, and, if he chooses to go ahead with the operation, refer him to our vascular surgeons. At the same time, I would emphasize to him the importance of lifestyle advice and treatment of cardiovascular risk factors and explain that the carotid stenosis is a reflection of a widespread disease process, which could result in stroke elsewhere in the brain and myocardial infarction.
The opinions expressed in this article are not necessarily those of the editors or of the American Heart Association. This article is Part 1 in a 3-part series. Parts 2 and 3 appear on pages 1154 and 1156, respectively.
- Received December 30, 2010.
- Revision received January 21, 2011.
- Accepted February 10, 2011.
- © 2011 American Heart Association, Inc.
- Rothwell PM,
- Goldstein LB
- Abbott AL
- Nicolaides AN,
- Kakkos SK,
- Kyriacou E,
- Griffin M,
- Sabetai M,
- Thomas DJ,
- Tegos T,
- Geroulakos G,
- Labropoulos N,
- Doré CJ,
- Morris TP,
- Naylor R,
- Abbott AL