Stroke is one of the three most common causes of death in the United States. A stroke is, in effect, a “brain attack”. The most common type of strokes occur when the blood supply to part of the brain is suddenly interrupted. These “thromboembolic” strokes have many causes. Many common risk factors are the same as those for heart disease: age, diabetes, high blood pressure, high cholesterol, smoking, unfortunate genetics. Symptoms of stroke depend on the area of the brain affected. If the blood supply to the area that controls the left limbs is interrupted, the limbs will be come weak. Aside from the usual cardiovascular risk factors, strokes have a couple of other discrete causes which are pretty interesting.
Thromboembolic strokes can originate in the blood vessels of the brain itself; if the blood vessels are affected by atherosclerosis, they can become acutely blocked causing a stroke. But strokes can also be caused when blood clots break off of the walls of other parts of the circulation and travel to the brain.
One common cause of stroke is atrial fibrillation. In this condition, the left atrium of the heart fails to contract normally and instead twitches irregularly. The relatively still blood in the atrium can clot, and these clots are shot into the left ventricle and from there through the aorta and then to the vessels that supply the brain.
Another common cause of stroke is plaque in the carotid arteries. Plaques build up in the carotid arteries much as the do in coronary arteries. These plaques can become unstable and send clots shooting up the carotid artery into the brain.
Strokes from atrial fibrillation can be prevented by the use of anticoagulants which prevent the formation of blood clots in the fibrillating atrium. The prevention of strokes from carotid artery disease is a bit more complicated. Many studies have evaluated the use of medication, surgery, and stenting for the prevention of strokes due to carotid artery disease. People with severe carotid artery disease often have warning signs of a stroke, such as brief, stroke-like symptoms called “transient ischemic attacks” (TIAs). In patients with such symptoms and with severe blockages of a carotid artery, evidence supports surgical repair of the carotid artery. This basically involves cutting it open and scooping out the nasty bit.
A newer procedure which is still under active investigation is “stenting”. Similar to , stenting of coronary arteries, stenting of a carotid artery involves threading a catheter from a let artery into the artery and opening it with a metal scaffold.
A study being released soon in The Lancet explored some of the risks and benefits of carotid artery stents. The study was widely reported this week, and some of the reporting was pretty lousy. Part of the problem may be that news outlets are relying on a press release or abstract, since this early release article is widely available. Many of the articles failed to cite the source. One report in particular failed completely to understand the medical facts behind the study.
It starts by announcing the main findings:
Stroke patients over 70 who get stents to keep their arteries open may be doubling their risk of having another stroke or dying compared to patients who get surgery instead, a new study says.
But it isn’t until halfway down the page that they (sort of) explain what kind of “stents” they are writing about:
In February, an American study found stents were as safe as surgery for treating narrow neck arteries. It also found the stents were more dangerous in patients older than 70.
As a medical professional, I suspected the article was about carotid artery stents, but I at first wondered if they could be talking about stroke risk related to coronary artery stents which would be a pretty dramatic new finding.
This sort of presentation adds further weight to the argument that reporters covering health topics must work to gain at least a minimal understanding of a topic before misreporting it.
Carotid Stenting Trialists’ Collaboration (2010). Short-term outcome after stenting versus endarterectomy for symptomatic carotid stenosis: a preplanned meta-analysis of individual patient data The Lancet : 10.1016/S0140-6736(10)61009-4
Chaturvedi, S. (2005). Carotid endarterectomy–An evidence-based review: Report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology Neurology, 65 (6), 794-801 DOI: 10.1212/01.wnl.0000176036.07558.82