Causes

Your heart is made up of four chambers — two upper chambers (atria) and two lower chambers (ventricles). The rhythm of your heart is normally controlled by the sinoatrial (SA) node — or sinus node — an area of specialized cells in the right atrium.

This natural pacemaker produces the electrical impulses that trigger the normal heartbeat. From the sinus node, electrical impulses travel across the atria to the ventricles, causing them to contract and pump blood to your lungs and body.

PVCs are abnormal contractions that begin in the ventricles. These extra contractions usually beat sooner than the next expected regular heartbeat. And they often interrupt the normal order of pumping, which is the atria first, then the ventricles.

Why do extra beats occur?

The reasons aren't always clear. Certain triggers, heart diseases or changes in the body can make cells in the ventricles electrically unstable. Heart disease or scarring may also cause electrical impulses to be misrouted.

Premature ventricular contractions can be associated with:

• Certain medications, including decongestants and antihistamines
• Alcohol or illegal drugs
• Increased levels of adrenaline in the body that may be caused by caffeine, tobacco, exercise or anxiety
• Injury to the heart muscle from coronary artery disease, congenital heart disease, high blood pressure or heart failure