What is bigeminy in a heartbeat?

Ask the doctor

Q. My aunt was having heart palpitations and recently found out that she has bigeminy. According to her doctor, it's not serious. But what exactly is this condition?

A. Bigeminy refers to a heartbeat marked by two beats close together with a pause following each pair of beats. The term comes from the Latin bigeminus, meaning double or paired (bi means two, geminus means twin).

This rhythm arises from a minor misfire in the heart's electrical system. The heart contracts a fraction of a second earlier than it should, triggering a premature beat. These usually occur in the heart's lower chambers (ventricles) and are known as premature ventricular contractions, or PVCs. It may feel as though the heart briefly stops and restarts. People often describe PVCs as a pounding or flip-flopping sensation. The heart's upper chambers (atria) can also contract a tad too soon, creating a so-called premature atrial contraction, or PAC.

Following either a PVC or PAC, the heart then pauses an instant longer afterward to get back into a normal rhythm. Because the ventricles must then contract forcefully to clear out the extra blood that accumulates during the pause, this can feel as though the heart has "skipped" a beat.

A person can have either ventricular bigeminy or atrial bigeminy. Both are fairly common and usually harmless. Possible triggers for these electrical glitches include caffeine, excessive amounts of alcohol, certain medications used to treat colds and allergies (decongestants), emotional stress, lack of sleep, dehydration, and thyroid disease.

PVCs can also occur in a pattern of three beats, known as trigeminy. This consists of two normal heartbeats followed by one extra beat.

Bigeminy may be detected with electrocardiography, which uses electrodes placed on the chest to painlessly record the heart's electrical activity. But the recording only lasts about six seconds, so if the premature beats occur only occasionally, this test won't uncover them. If that's the case, the doctor may recommend a Holter monitor, which records the heart's electrical activity for 24 to 48 hours using a wearable monitor that's about the size of a small camera and is attached to the chest electrodes.

People with frequent, bothersome symptoms from bigeminy may need medications such as beta blockers, which slow down the heart and reduce the force of its contractions. In rare cases, the condition affects how well the left ventricle works. If that happens, cardiologists may recommend catheter ablation, a procedure that creates tiny lesions in the abnormal heart tissue to stop the errant electrical signals responsible for the bigeminy heartbeat.

— Deepak L. Bhatt, M.D., M.P.H.
Editor in Chief, Harvard Heart Letter

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