What is ventricular bigeminy?

Q. What does it mean when the doctor diagnoses a condition called ventricular bigeminy? What are its causes and symptoms, and is it ever dangerous?

A. Bigeminy refers to an abnormal heart rhythm marked by a repeating pattern of two beats close together, followed by a pause. For most people, bigeminy is harmless, especially if your heart is otherwise healthy.

The pattern happens when the heart contracts a fraction of a second earlier than it should, triggering a premature beat. These contractions typically occur in the heart's lower chambers (ventricles) and are known as premature ventricular contractions, or PVCs.

After a PVC, the heart pauses an instant longer afterward to get back into a normal rhythm. The ventricles must then squeeze more forcefully than usual to clear out the extra blood that accumulates during the pause. It may feel as though the heart briefly stops and restarts, or as though the heart has "skipped" a beat. Some people say it feels like a pounding or flip-flopping sensation in their chest. PVCs can occur randomly in isolation, but ventricular bigeminy is when every normal heartbeat is followed by a PVC.

The heart's upper chambers (atria) can also contract too soon, creating what's called a premature atrial contraction, or PAC. When these occur in succession, it's known as atrial bigeminy. This form of bigeminy is milder and often goes unnoticed. People can also have trigeminy, which consists of a PVC or PAC followed by two normal heartbeats.

The irregular electric signals that underlie bigeminy have many possible triggers, including

• caffeine
• nicotine
• excessive amounts of alcohol
• certain medications used to treat asthma, colds, and allergies
• emotional stress or anxiety
• lack of sleep
• dehydration or abnormal electrolyte levels.

Thyroid disorders, anemia, and cardiovascular conditions that affect the heart, including high blood pressure and heart attacks, can also contribute to the problem.

Often, bigeminy resolves on its own. However, some people newly diagnosed with bigeminy need further evaluation, especially if they develop symptoms such as lightheadedness, dizziness, chest pain, shortness of breath, or unexplained fatigue. It starts with a careful analysis of an electrocardiogram, which records the heart's electrical activity for a few minutes. Other tests may include a heart ultrasound (echocardiogram) to check for heart muscle abnormalities and wearing a small device that continually monitors the heart's electrical activity for a couple of weeks.

Occasionally, an underlying heart muscle disorder causes ventricular bigeminy. And sustained ventricular bigeminy that persists for months or years can wear down the heart muscle, leading to weakness. But both of these situations are uncommon, and the majority of people with bigeminy have no heart muscle weakness.

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