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Medical Therapy Alone May Not Prevent Substantial Asymptomatic Carotid Stenosis

Key findings

  • Complete vessel occlusion was the culprit in 43% of carotid-related strokes in patients who previously had no symptoms
  • Among previously asymptomatic patients who suffered a carotid-related stroke, those on antiplatelet plus lipid-lowering therapy were significantly less likely than those on other drug regimens to experience severe impairment
  • Yet even patients receiving appropriate risk-reduction medical therapy were at risk of carotid-mediated stroke

Optimal management of patients with asymptomatic carotid stenosis is currently controversial. Some experts argue that given the improvements in medical therapy for stroke prevention, carotid endarterectomy or angioplasty with stenting should be reserved for symptomatic patients.

In a large retrospective study, researchers at Massachusetts General Hospital determined just the opposite. Medical therapy alone is unlikely to provide sufficient stroke prevention for patients with significant carotid stenosis.

Researchers including Derek Klarin, MD, resident in surgery, Mark Conrad, MD, director of Clinical Research, Division of Vascular and Endovascular Surgery, published these findings in the Journal of Vascular Surgery as an editors' choice from the 2017 meeting of the New England Society for Vascular Surgery.

The researchers reviewed the records of 3,382 patients admitted for first-time ischemic stroke between 2005 and 2015. They focused their study on the 219 patients (7%) whose infarct was ipsilateral to the side of ≥50% carotid artery stenosis and had been judged by the admitting neurology team to be carotid-related.

Medical Therapy Can Reduce Stroke Severity

Of these patients, 145 had a National Institutes of Health stroke score (NIHSS) assigned in the emergency room. Altogether, 103 (71%) of them were judged to have had a moderately or severely debilitating stroke (NIHSS ≥5). In that group, patients who had been receiving both antiplatelet and lipid-lowering therapy were significantly less likely than those receiving other therapies to have experienced a debilitating stroke (44% vs 78%; P=.006).

Yet, 35% of the 219 patients who had carotid strokes were taking both an antiplatelet agent and lipid-lowering therapy, the regimen considered appropriate for stroke prevention and atherosclerotic risk modification.

Furthermore, before their stroke admission, only 7% of the patients had carotid stenosis visualized ipsilateral to the subsequent infarct on at least one imaging examination (duplex ultrasonography, magnetic resonance angiography or computed tomography angiography). The researchers emphasize that asymptomatic carotid disease often goes unrecognized, and the first manifestation can be a stroke.

High Prevalence of Complete Occlusion

The affected carotid arteries in the patients were categorized as >50% to 70% stenosed, >70% stenosed, or completely occluded. Close to half of patients (43%) had an occluded vessel as the cause of their stroke, the researchers found, and only 9.5% had 50% to 70% stenosis.

Patients with stroke due to an occluded carotid artery are ineligible for later revascularization, the researchers note. Moreover, previous research has shown that unilateral occlusion increases future stroke risk—and may exacerbate the perioperative risk if contralateral carotid revascularization ever becomes necessary.

When assessing the risks and benefits of carotid revascularization in asymptomatic patients, interventionists should consider this inability to salvage carotid perfusion in patients with occlusion, the authors recommend.

Advice for Clinicians

The researchers conclude that although appropriate medical therapy can reduce the severity of carotid atherosclerotic disease, it does not completely eliminate stroke risk in patients with substantial stenosis.

They advise proper identification of stenosis, initiation of medical therapy, proper surveillance for progression, and revascularization as important ways to minimize progression to carotid-related stroke.

7%
of ischemic strokes were carotid-related

35%
of patients had carotid strokes despite optimal medical therapy

93%
of patients had no imaging of carotid stenosis prior to stroke

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