When a lean, healthy, physically active person has a stroke, seemingly out of the blue, the cause may well be a heart rhythm abnormality called atrial fibrillation.
Such was the fate of Pamela Bolen of Brooklyn, then 67, who said she collapsed last year at home. Luckily, her husband, Jack, heard her fall, called an ambulance, and within minutes she was at New York Methodist Hospital. There she was given the drug tissue plasminogen activator, or tPA, to dissolve the clot that was blocking circulation in her brain. The treatment spared her lasting disability.
"I had high blood pressure which was completely controlled with medication, but I didn't know I had atrial fibrillation until I had a stroke," Ms. Bolen said in an interview. The condition slows blood flow from the heart and was the likely cause of the clot that resulted in her stroke.
About three million Americans have atrial fibrillation, characterized by multiple irregular electrical signals that cause the heart's upper chambers, the atria, to contract rapidly, without their usual coordination. This sends an erratic signal to the ventricles, the lower chambers that supply blood to the lungs and rest of the body. People with the disorder face a much higher risk of stroke, and most require treatment to prevent this potentially crippling and sometimes fatal consequence.
"As many as one in five or six strokes is due to atrial fibrillation, and in a lot of these people the rhythm disorder was undetected before the stroke," said Dr. Christian T. Ruff, cardiologist at Brigham and Women's Hospital in Boston, who studies new treatments for the disorder.
People with symptomatic A-fib, as it is commonly called, may experience periodic palpitations (a sense that the heart is pounding or fluttering), chest discomfort, shortness of breath, unusual fatigue or dizziness.
A-fib can show up during an electrocardiogram, or EKG, but because the abnormal rhythm may not occur all the time, people suspected of having the condition usually must wear a Holter monitor for days or weeks to obtain a certain diagnosis. This small portable device, connected to electrodes on the chest, continuously records the heart's rhythm and sends the data to a doctor or company for evaluation.
A-fib is more common in men, tall people and the elderly. As the population ages, the incidence is rising; more than 460,000 new cases are diagnosed annually, a number expected to double in the next 25 years. The condition is also becoming more prevalent at any age, experts say, because of a rise in three leading risk factors — high blood pressure, diabetes and obesity.
These conditions can damage the heart's electrical system, Dr. Ruff wrote last year in the journal Circulation. Other risk factors include a prior heart attack, overactive thyroid, sleep apnea, excessive alcohol consumption, abnormal heart valves, lung disease and congenital heart defects.
Researchers at the University of California, San Francisco, reported this month in Annals of Internal Medicine that people with a high rate of premature atrial contractions, which can be detected by a Holter monitor worn for 24 hours, face a significantly increased risk of developing A-fib. Dr. Gregory M. Marcus, the senior author and director of clinical research at U.C.S.F.'s cardiology division, theorized that eradicating these premature contractions with drugs or a procedure that destroys the malfunctioning area of the heart may reduce the risk of the rhythm disorder.
Step 1 in treating A-fib is to identify and correct reversible risk factors. Step 2 — and most important, according to Dr. Ruff — is to prevent blood clots from forming by treating patients with anticoagulants.
The most commonly prescribed and least costly treatment is warfarin, also known by the brand name Coumadin, in use for more than half a century. But while highly effective at reducing the risk of stroke, warfarin is a very tricky drug. It interacts with a number of foods, especially those like spinach and kale that are rich in vitamin K, and other drugs that a patient may have to take.
People metabolize warfarin at different rates, making it necessary to repeatedly check a patient's clotting ability to reduce the risk of excessive bleeding while maintaining an effective anticoagulant level.
Dr. Ruff said that more than half of A-fib patients were either not on an anticoagulant or on an ineffective dose. Fearful of a hemorrhage in the brain, or uncontrolled bleeding in an accident or emergency surgery, doctors may prescribe an amount of warfarin insufficient to prevent a stroke, he said.
This concern has spurred the development of several other anticoagulants that are considerably safer and easier to take, but also far more expensive than the generic warfarin. The Food and Drug Administration has already approved three such medications — apixaban (Eliquis), dabigatran etexilate mesylate (Pradaxa) and rivaroxaban (Xarelto) — and others are being studied.
Patients with A-fib are also often prescribed drugs to normalize the rate and rhythm of the heart's contractions. Ed Goldman, 73, of Manhattan, who was found to have A-fib 17 years ago, takes amiodarone hydrochloride (Cordarone) and verapamil (Calan and other brand names), and said in an interview that he rarely experienced a slight increase in his heart rate.
Sometimes an electrical shock to the heart, called cardioversion, is used to restore a normal rhythm.
For some patients, however, neither medication nor cardioversion is able to maintain normal heart rhythm. An invasive procedure called ablation is needed to knock out the area or areas of the heart sending out errant signals. A catheter is inserted into a vein, usually through a small cut in the groin, and snaked up to the heart. Small electrodes placed in the heart identify malfunctioning areas, which are then destroyed.
Last year, Dr. Sanjiv Narayan, an electrophysiologist at the University of California, San Diego, and co-authors described a way to more accurately identify the electrical "hot spots" in the heart responsible for an abnormal rhythm. Ablating those regions was nearly twice as effective as the standard approach to eliminating atrial fibrillation with ablation, the team reported in The Journal of the American College of Cardiology.
But even when all traces of A-fib are eliminated, Dr. Ruff said, continued treatment with an anticoagulant is needed to guard against stroke. "Once a person has had A-fib, there is an increased risk of stroke even if their heart is in normal rhythm," he said.
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