The study examined records from 503 patients who had been tested for coronary endothelial dysfunction (CED), a disorder in the arteries that supplies blood to the heart. The endothelium is a thin layer of cells that lines all of the blood vessels in the body and regulates blood flow. In patients with CED, a stimulus that would normally cause vessels to expand and increase blood flow in response to challenge fails to do so, and may even cause contraction. This leads to symptoms such as chest pain.
"We believe that CED is a key early stage of coronary artery disease, and that the damage to this blood-vessel lining is also an important contributor to the subsequent formation of blockages," says Amir Lerman, M.D., who directs the Mayo Clinic Chest Pain and Coronary Physiology Clinic and led the stroke study. "Now, with the linkage between CED and stroke, we see the same kind of process at work in the arteries of the brain."
In the Mayo Clinic study, patients with CED had five times as many strokes or transient ischemic attacks (TIAs) as those with normally functioning endothelium. Even after adjusting for other risk factors such as age, diabetes, hypertension, smoking history and obesity, CED remained the single strongest factor associated with stroke or TIA. Patients who had significant blockages in their heart arteries, as determined by coronary angiography, were not included in the study. Angiography involves injecting a dye into one of the heartÕs major blood vessels and using X-rays to monitor its flow into the coronary arteries. Endothelial function testing is similarly invasive and is used for patients whose angiograms show no obstructions keeping blood from the heart. "Many of the patients we see in the Chest Pain Clinic have made numerous trips to the emergency room and have had repeated angiograms," says Dr. Lerman. "Our endothelial-function testing helps us find answers and treatments now for these patients with unexplained chest pain. But this research may have even more important implications in identifying people at risk for heart attack and stroke before they have significant symptoms." Currently, CED testing is invasive and expensive, and therefore inappropriate for widespread use. Because the endothelium is part of all arteries, not just those in the heart and brain, Dr. Lerman and others are working on a test that could screen for this dysfunction in fingertip blood vessels. "Screening for endothelial dysfunction could potentially identify patients who would benefit from aggressive treatment of other risk factors," concludes Dr. Lerman. "Now that we have associated this disorder with both heart attack and stroke, finding ways to identify it earlier in patients is even more important."
Other authors of the paper include Paul Targonski, M.D., Ph.D.; Piero Bonetti, M.D.; Geralyn Pumper, Stuart Higano, M.D. and David Holmes, M.D. The study was supported by the National Institutes of Health, the American Heart Association and Mayo Foundation.
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Monday, June 9, 2003
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