Ventricular Arrhythmias

Premature ventricular contractions (PVCs) are the most common cause of irregular heart rhythms.

The heartbeat is created by an electrical signal that originates in an area of specialized cells in the heart’s upper right chamber, the right atrium. The electrical signal moves down through the heart to the atrioventricular (AV) node, a cluster of specialized cells in the center of the heart. From the AV node the signal passes along special fibers embedded in the heart walls to the ventricles, the lower chambers. When the electrical current arrives in the ventricles, it causes them to contract and pump oxygen-rich blood out to the body.

What are premature ventricular contractions?

A premature ventricular contraction (PVC) is a too-early heartbeat that originates in the ventricles and disrupts the heart’s normal rhythm. The pattern is a normal beat, an extra beat (the PVC), a slight pause, then a stronger-than-normal beat. The heart fills with more blood during the pause following the PVC, giving the next beat extra force. This pattern may occur randomly or at definite intervals.

Who is at risk for PVCs?

Almost everyone has PVCs at some time, from childhood through adulthood. In a study of healthy members of the military, the incidence of PVCs was 0.5% among those under the age of 20 and 2.2% in those over the age of 50. This study shows the rise in PVCs – as in all types of abnormal heart rhythms – that occurs with age. PVCs occur more commonly in older people and in individuals with underlying heart disease, including a history of heart attack. People with a family history of cardiac arrhythmias (abnormal heart rhythm) also have a higher risk for PVCs.

What causes PVCs?

Healthy people of any age can experience PVCs. In most cases of occasional PVCs the underlying cause cannot be identified.

PVCs that occur frequently or for longer periods of time are more likely to be related to heart disease, an injury to the heart or other, non-cardiac conditions such as a chemical imbalance in the body. Certain medications, alcohol, illegal drugs and high levels of adrenaline due to stress, exercise or caffeine also can cause PVCs.