Arrhythmia 101

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By Michele Meyer

Whether it's a gentle flutter or a pounding drum, a chaotic heartbeat can be frightening. Some causes are harmless. Others require a doctor's help.

One minute, Karen Krakower’s thoughts drifted at a Parent-Teacher Association meeting. The next minute she remembers vividly. ‘’All of a sudden, I felt like I was going to pass out,‘’ says Krakower, 51, an online editor at University of Texas at Houston. ‘’It was as if someone had pulled the plug to my electrical source. My head started to drop, and then I was fine. I instinctively put my fingers to my pulse. The rhythm was off: It was doing the samba and should have been doing the fox-trot.’’

As a teen, you may have accepted a racing heart as a reaction to a romantic crush. As an adult, when your heart thumps wildly in your chest, you can’t easily dismiss it. “It feels like you’re having an anxiety attack,’’ Krakower says.

Such palpitations alert us that our heartbeat is off track, whether it’s too fast, too slow, or erratic. “We see abnormal heartbeats in everybody, at any age, though more frequently in patients in their late 50s and older,’’ says Andrea Natale, M.D., head of pacing and electrophysiology at Cleveland Clinic in Ohio.

How Your Heart Beats
Even though it’s common, a fast-fluttering heartbeat can be frightening. After all, year after year, your heart follows its normal cadence: a seamless flow of electrical impulses that runs through the upper two heart chambers (or atria), then passes through the atrioventricular node—the divider between the upper and lower heart—to reach the lower two chambers (or ventricles). This electricity causes the upper chambers to contract, pushing blood into the lower chambers. In turn, the lower chambers contract, pumping blood to your body.

That electrical dance occurs between 60 and 100 times a minute—or as many as 144,000 times a day. Age, activity, diet, and drugs all may slow or quicken the process, and your heart may reach 180 beats per minute during intense exercise.

But when your heart races up to 400 beats per minute—for no known reason—it may alarm you and your doctors. Too fast a dance, and the lower heart may be unable to fill with enough blood to pump out to your vital organs. You become oxygen-deprived, which can cause shortness of breath, chest pain, dizziness, blackouts, or death.