Harvard Heart Letter

Be still, my beating heart

Heart palpitations can be alarming, but are they dangerous?

heart palpitations
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Do you ever feel that your heart is pounding, skipping, or racing so fast that you're certain it will explode from your chest at any moment? That's how many people describe the experience of heart palpitations. In the most literal sense, palpitations are simply an awareness of your heart beating, says Dr. William Stevenson, professor of medicine at Harvard-affiliated Brigham and Women's Hospital. The most familiar trigger for palpitations is heavy exercise, such as when you pedal extra hard to summit the last computerized hill in your indoor cycling class.

Skipping a beat

Although common, palpitations alarm many people, in part because they tend to come on unexpectedly. Isolated palpitations typically occur when a small rush of adrenaline courses through your body, causing your heart to beat more forcefully than usual. These surges can be generated by a strong emotion such as excitement, fear, or anger. They also can come on after consuming a stimulant such as caffeine.

Another common source of palpitations is premature contraction of the atria. When the heart's upper chambers squeeze a fraction of a second earlier than they should, they rest an instant longer afterward to get back to their usual rhythm. This feels like a skipped beat. It is often followed by a noticeably forceful contraction as the ventricles clear out the extra blood they accumulated during the pause. These premature beats are almost always benign, meaning they aren't life-threatening or the sign of a heart attack in the making. "Everyone has a few of these premature beats once in a while, and they tend to increase with age," says Dr. Stevenson.

More serious concerns

The sensation of abnormal heartbeat can also be a warning sign of a heart rhythm problem. A sustained fast or irregular heart rhythm originating in either the upper or lower chambers can result in distressing symptoms such as lightheadedness, dizziness, or shortness of breath. At their most serious, these rhythm abnormalities may lead to complications such as stroke and even sudden death if the ventricles contract so chaotically that blood doesn't move out of the heart. So if you start having palpitations or irregular heartbeats that you haven't noticed before, it's wise to get checked out, says Dr. Stevenson. This is especially important if you are having worrisome symptoms such as shortness of breath or chest pain.

When listening to your heart, your doctor may hear a murmur or other sound suggesting a problem with one of the heart's valves, which can cause palpitations. Testing may also reveal a thyroid imbalance, signs of anemia, low potassium, or other problems that can cause or contribute to palpitations. Your exam may also include electrocardiography (ECG) and echocardiography, an ultrasound of the heart, to assess your heart's electrical activity and pumping ability.

However, since palpitations tend to come and go, there's a good chance they won't turn up during your doctor's visit, and your doctor may need to do more detective work. A portable ECG recorder (called a Holter monitor or an event monitor) that you wear continuously from 24 to 48 hours or up to one month captures episodes of abnormal heart activity as you go about your daily routine. There's even an implantable recorder that can invisibly monitor the heart for a year or more. This device may be needed if your bouts of irregular rhythms are particularly sporadic.

When treatment is needed

Once serious causes have been ruled out, most people who have isolated palpitations simply need reassurance that nothing dire is happening, says Dr. Stevenson. If you're still bothered by unexplained palpitations, start with simple things first. Low blood sugar can trigger palpitations, so make a point of eating regularly. Drinking plenty of fluids and getting enough sleep may also help. Since stress and anxiety are a source of palpitations in many people, breathing exercises, meditation, or other relaxation techniques may do the trick. Nicotine can cause palpitations, as can alcohol and over-the-counter decongestant medications that contain pseudoephedrine or phenylephrine.

When self-care measures aren't enough, certain drugs may help. Beta blockers that quell the effects of adrenaline on the heart can successfully combat most types of fast heart rhythms. Some people may get relief with anti-anxiety medicines.

If your ECG shows a particular type of abnormal heart rhythm, your doctor may suggest a procedure called catheter ablation to correct it. A thin tube (catheter) is guided into the heart, and a jolt of radiofrequency energy is applied to destroy a faulty electrical pathway in the heart muscle that is responsible for the erratic signaling. For potentially fatal rhythm abnormalities coming from the ventricles, an implantable cardiac defibrillator that resets those rhythms can be a lifesaver.

Possible palpitation triggers

  • Stress, anxiety, or panic

  • Dehydration

  • Low potassium or magnesium

  • Low blood sugar

  • Too much alcohol or caffeine

  • Nicotine

  • Exercise

  • Fever

  • Menopause

  • Heartburn

  • Street drugs such as cocaine and amphetamines

  • Medications such as diet pills, some cough and cold remedies, some antibiotics, thyroid hormone, digoxin, or asthma remedies

  • Dietary supplements such as ephedra, ginseng, bitter orange, valerian, or hawthorn