Healthy Living News

Fast Heartbeat May Raise Stroke Risk

by Robert H. Shmerling, M.D.
Harvard Medical School

People with a very fast heartbeat that is not causing symptoms may still have a higher risk of stroke, new research finds. The study included 2,580 older adults with high blood pressure. All of them had a pacemaker or defibrillator implanted to help control their heart rhythm. This device kept a record of the speed and rhythm of their heart over time. None of the people had a known history of atrial fibrillation. This is a very fast, irregular rhythm in the heart's upper chambers. It causes them to quiver rather than beat normally. Soon after the study started, the devices recorded a very rapid heartbeat that lasted several minutes in about 1 out of 10 people. They usually had no symptoms. But in the next 2 ½ years they were more likely to develop lasting atrial fibrillation. They also were more likely to have a stroke. The New England Journal of Medicine published the study. HealthDay News and MedPage Today wrote about it January 11.

What Is the Doctor's Reaction?

During a stroke, a part of the brain dies. Strokes can cause major disability. It's not rare to lose your ability to walk, speak or live independently. And strokes can kill. That's why we need better ways to prevent strokes from occurring in the first place.

We have seen advances in the understanding and treatment of strokes. But still nearly 800,000 are diagnosed in the United States each year. About 140,000 people die each year from complications of strokes.

High blood pressure and diabetes are strongly linked with a higher risk of stroke. We do have good ways to prevent and treat those conditions. But the cause of up to 25% of strokes is unknown. A new study suggests a potential explanation for many of these.

Researchers took advantage of a "side benefit" of having a device, such as a pacemaker or a defibrillator, implanted in the heart. These devices record the rhythm of the heart. That way they can take control of the heart rhythm when necessary. For example, a pacemaker may start firing when the heart slows down to a dangerously low rate. A defibrillator will "reset" the heart with an electrical shock if it detects a dangerous and unstable heart rhythm.

These heart devices can also record fast heart rhythms. One abnormal rhythm, called atrial fibrillation, is known to increase the risk of stroke. During atrial fibrillation, the top part of the heart does not beat in a regular rhythm. Instead, it quivers in a chaotic way. This allows blood clots to form. They can travel to the brain, causing a stroke.

This new study included more than 2.500 people over age 65. All of them had recently implanted heart devices. Researchers used data from these devices to explore the relationship between fast heart rhythms and stroke risk. The study lasted 2½ years. In that time:

• About 10% of study subjects had lengthy episodes of a rapid heart rate
• These rapid rhythms (which caused no symptoms) were often followed by atrial fibrillation
• A rapid heart rate that lasted for a while was linked with an increased risk of stroke even if no atrial fibrillation occurred

But this isn't the end of the story. Several questions remain:

• Did the implanted heart devices contribute to the rapid heart rates?
• Do the findings of this study apply to people who do not have heart disease bad enough to require an implanted heart device?
• Do the findings of this study apply to younger patients?

These findings suggest that a rapid heart rate might account for many strokes in people without other clear risk factors. And that could lead to new preventive treatments.

What Changes Can I Make Now?

You may be able to reduce your risk of developing atrial fibrillation or other rapid heart rhythms that increase the risk of stroke. Here's what you can do:

• Avoid heavy drinking of alcohol.
• Don't smoke.
• Lose excess weight.
• Exercise regularly.
• Get your blood pressure checked. Get treatment if it's high.
• Have tests of your thyroid gland if you're taking thyroid medicine.

If you already have atrial fibrillation, your doctor may recommend treatments such as:

• Medicines to slow the heart
• Medicines to encourage the heart to remain in a normal, regular rhythm
• Blood thinners, to prevent clots
• A minor heart procedure to interrupt signals traveling between the chambers of the heart (though this may require an artificial pacemaker)

Besides an abnormal heart rhythm, several other factors increase the risk of stroke. Many of them can be reversed. The most important of these and ways to address them include:

• Lack of exercise -- Try to get regular exercise for at least 45 minutes most days of the week.
• Smoking -- Make quitting a priority.
• High blood pressure (hypertension) -- Have your blood pressure checked. If it's high, limit your salt intake and lose excess weight. If necessary, take medicines that your doctor recommends.
• Diabetes -- Try to maintain tight control of your blood sugar. This may lower your risk of further health problems, including stroke.
• High cholesterol -- If your HDL, LDL and total cholesterol are not in ideal ranges, talk to your doctor about how to improve them.
• Carotid artery narrowing -- These arteries are in the neck and supply blood to the brain. Sometimes they become narrowed by a buildup of fatty deposits inside. A surgical procedure can open up the artery, reducing stroke risk.

What Can I Expect Looking to the Future?

It's hard to prevent something when you don't know its cause. This latest research suggests that an abnormally fast heart rate may increase the risk of stroke. Expect to hear about more research that examines ways to detect and treat rapid heart rhythms. It's quite possible that this approach will reduce new cases of stroke.

Categories: Heart Health, Men's Health, Women's Health, Stroke

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