Poets and novelists say it can be a sign of love. However, a racing and skipping heart is more likely to signal a heart rhythm abnormality than romance. In this Health Alert, Johns Hopkins discusses the connection between atrial fibrillation and stroke.
Atrial fibrillation (AF) is the most common heart rhythm disorder in the United States, affecting an estimated 2.3 million individuals. It occurs when the upper chambers (atria) of the heart beat rapidly and chaotically, which can cause the pulse rate to jump to over 100 beats per minute and interfere with the heart's pumping efficiency.
However, AF does not just reduce the amount of blood pumped with each heartbeat; it can also increase the risk of an ischemic stroke. In fact, a third of those with untreated AF will have a stroke, and one in six strokes occur in people with AF.
What are the Causes of AF–Related Strokes?
Atrial fibrillation is the result of an electrical glitch that upsets the normal rhythm of the heart. Electrical impulses in the atria that normally produce a continuous smooth wave of contractions begin to fire in a rapid and erratic manner. This creates an irregular heartbeat and inefficient pumping that does not completely empty the atria of blood. If this situation continues for prolonged periods of time, the blood left behind in the atria may form clots. If a clot breaks loose, leaves the heart, and lodges in an artery in the brain, the result is a stroke.
Who's At Risk?
Everyone with AF is at risk for a stroke, but some people are at greater risk than others. These include individuals who have already had a stroke or transient ischemic attack (TIA) as well as people over age 75 and those with hypertension, heart failure, or diabetes. The risk is also high in people with mitral valve stenosis or artificial heart valves.
To quantify stroke risk in individuals with nonvalve-related AF, physicians calculate something called a CHADS2 risk score. Each letter in CHADS2 stands for a different risk factor: C is for congestive heart failure; H, for hypertension; A, for age; D, for diabetes; and S, for stroke. The number two indicates that a history of stroke is associated with double the stroke risk of any of the other four risk factors.
Reducing the Risk
If you have AF, receiving treatment to prevent a stroke is just as important as slowing the rapid heartbeat and, if possible, restoring the heart's normal rhythm. In fact, even when heart rate and rhythm are back to normal, research shows that the risk of stroke persists and thus medication to prevent strokes is still required.
The stroke prevention strategy that you and your physician choose will depend on your CHADS2 score. If the score is 0, a daily aspirin (81–325 mg) is sufficient to minimize blood clot formation and reduce your risk of stroke. But if the score is 2 or more, the stronger anticlotting medication warfarin (Coumadin) is recommended.
Warfarin is more effective than aspirin against AF–related strokes; however, it is also more likely to result in serious side effects such as gastrointestinal bleeding and hemorrhagic stroke. Therefore, in someone with a low risk of an AF–related stroke (a CHADS2 score of 0), the increased risk of life-threatening bleeding with warfarin does not outweigh its stroke- preventative benefits. But in those at high risk for stroke (a CHADS2 score of 2 or more), the benefits do outweigh the risks.
So what about those people with a CHADS2 score of 1? These individuals can choose between warfarin or aspirin. When making the decision, their physicians will take into consideration their bleeding risk, but often it simply comes down to personal preference. For example, someone who is highly concerned about having a stroke will choose warfarin, whereas a person who feels inconvenienced by the dietary and physical activity restrictions or the frequent monitoring required with warfarin typically elects for aspirin.
