Carotid stenosis is not a ‘ticking time bomb’ according to Schulich Medicine & Dentistry researcher
Dr. David Spence and a team of researchers have determined that preventing occlusion (blockage) of a carotid artery may not be a valid reason for surgical intervention in all patients with asymptomatic carotid stenosis (narrowing of the carotid artery, without symptoms).
Dr. Spence’s research, published in JAMA Neurology, demonstrates that at the time of a new carotid occlusion – when the artery becomes completely blocked – only one out every 316 patients (0.32 per cent) had a stroke at the time the artery occluded.
He studied 3,681 patients, referred between 1992 and 2012, who had been followed with annual carotid ultrasound examinations.
Carotid stenosis is often regarded as similar to a blocked artery in the heart. The assumption is that the risk of stroke is high when the carotid artery is blocked, as is the case with heart attacks when a large coronary artery is blocked.
In contrast to the heart, the circulation of the brain is protected by a natural bypass, the Circle of Willis, which connects all the main arteries supplying blood to the brain. So, if one artery, such as a carotid artery, becomes blocked, the other arteries can supply blood to that part of the brain.
Current medical guidelines recommend either endarterectomy – surgery to remove the plaque from the artery, or the placement of a stent – a small, mesh tube placed in the artery – to prevent a possible stroke.
The 30-day risk of stroke or death for asymptomatic patients is 1.4 per cent for endarterectomy and 2.5 per cent for stenting. The four-year risk of stroke or death rises to 2.7 per cent for endarterectomy and 4.5 per cent for stenting in randomized trials.
However, with modern medical therapy, 90 per cent of patients have a 0.5 per cent annual risk of stroke, well below the risk of stroke from stenting or surgery.
The 10 per cent of patients who could potentially benefit from surgery can be identified by listening to the arteries with ultrasound (transcranial Doppler) to detect small chunks (microemboli) breaking off the plaque that narrows the artery. Those patients have a one-year risk of 15.6 per cent for developing strokes, so would be likely to benefit from intervention.
“Treating arteries instead of treating risk factors reduces the risk of stroke or heart attack by more than 80 per cent,” said Dr. Spence. “Most people with carotid stenosis are better off without surgery. Carotid stenosis is not a ticking time bomb, and doing surgery or stenting for the purpose of prevention a stroke is probably unwarranted.”