Stroke Risk Eyed in Those With Bad Heart Rhythm
07 January, 2014
ISLAMABAD: Doctors have found a new tool to help ward off strokes among people with abnormal heart rhythms.
The tool, a new risk score, is important to the more than 2 million Americans with atrial fibrillation, a disorder in which the two upper chambers of the heart lose their ability to pump blood forcefully. Clots that form in these atria can block blood vessels and cause strokes; 15 percent of all strokes occur in patients with atrial fibrillation, says the American Heart Association. The risk score emerged from the long-running Framingham Heart Study.
Five factors are associated with high risk of stroke, says a report in the Aug. 27 issue of the Journal of the American Medical Association: being old, being a woman, having high systolic blood pressure (the higher of the two blood pressure numbers), having a previous stroke or a short-term artery blockage, and having diabetes.
For example, a 75-year-old man with a 150 systolic reading and diabetes, but no previous stroke, gets a score of 16, indicating a 16 percent risk of stroke in the next five years.
A more complex analysis, including other factors such as smoking, can help determine the risk of death, says study author Dr. Thomas J. Wang, a Framingham researcher who is an instructor in medicine at Massachusetts General Hospital.
The risk scores were developed by following 705 patients newly diagnosed with atrial fibrillation who were not given the widely used blood thinner warfarin for four years, Wang says.
"The algorithm [risk score] is similar to that developed for risk of heart disease in the Framingham study," Wang says.
The new risk score is far from perfect, he acknowledges. "It still must be tested in the general population," Wang says. "But it raises the awareness of the risk of stroke in patients with atrial fibrillation."
Too many atrial fibrillation patients who would benefit from warfarin are not being prescribed the medication, says an accompanying editorial by Dr. Albert L. Waldo, a professor of cardiology and medicine at Case Western Reserve University.
One major reason is that warfarin is an extremely difficult drug to manage, he says, because it interacts not only with many other medicines but also with many foods.
People who take warfarin can't drink alcohol or eat broccoli, lettuce or other green, leafy vegetables, among other restrictions. "This study shows that doctors can dial up and show a patient's risk of stroke and death," Waldo says. "We hope it can overwhelm doctors' reservations about using warfarin."
One reason for those reservations is that any patient taking warfarin must have a blood test every two or three weeks to be sure that the blood-thinning level is low enough to avoid clotting but not so low as to cause dangerous bleeding, Waldo notes.
But there is hope that a new blood thinner now in advanced clinical trials could remove most of those complicating factors, Waldo says. The medication, Exanta, being developed by the AstraZeneca pharmaceutical company, is being used in several large-scale trials involving thousands of patients.
Initial reports of those trials have been extremely encouraging, and there is hope that the drug will be put on a fast track for approval by the U.S. Food and Drug Administration to make it available by the end of next year, Waldo says.
The value of the risk score for stroke in atrial fibrillation would increase greatly if and when an easier-to-manage blood thinner becomes available, he says.