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DEAR DR. ROACH: You recently used the term "abnormal irregular heartbeat." I've had an irregular heartbeat for decades without seemingly ill effects. My doctors haven't put any restrictions on my vigorous cycling or any other activities that I do at 84 years old. Does this mean that I have normal irregular heartbeats? Is there an implied difference by your use of "abnormal"?
-- S.B.
ANSWER: The answer is more complicated than it might seem. A perfectly regular heartbeat is, perhaps counterintuitively, not normal. The heart should respond to subtle changes in chest pressure due to breathing -- a condition that's called sinus arrhythmia. Although it sounds bad, it's a sign of a healthy heart. People with lower-than-average variability in their heart rate -- such as people who've recently had a heart attack or those who've had heart failure -- often have an increased risk of bad outcomes.
There are other common irregular heartbeats, especially premature atrial contractions and premature ventricular contractions. An average person without heart problems may have hundreds of these per day. The majority of people have at least a few of these a day, so I'd call these "normal irregular heartbeats." However, some people have thousands of these daily, which can be enough to cause symptoms, so they aren't always entirely benign.
By contrast, there are a wide variety of abnormal irregular heartbeats. In the recent column that you're referring to, the issue was specifically atrial fibrillation -- a common rhythm disturbance that can cause heart symptoms and strongly predisposes people to blood clots, which can cause strokes.
Other rhythm disturbances can be immediately fatal (ventricular fibrillation), rapidly life-threatening (ventricular tachycardia), or symptomatic and potentially dangerous (paroxysmal atrial reentrant tachycardia). An entire branch of cardiology (electrophysiology) is devoted to the study and treatment of rhythm disorders.
I don't know enough about you to be sure what you have, but the fact that you have excellent exercise tolerance at 84 and your doctors don't have any apparent concerns suggest that severe abnormalities are very unlikely.
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Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu.
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