Premature Beats

Premature beats (contractions) are beats that occur earlier than expected and briefly interrupt the normal heart rhythm. Premature beats are the most common cause of an irregular heartbeat. Although they tend to be more common in people with heart disease, almost everyone experiences them at least occasionally. Premature beats often cause a sensation of a "skipped beat" or "flip-flop." What are really felt are not the premature beats themselves but rather the forceful beat that follows the pause after the premature beat. During the pause, the heart has more time to fill with blood making the next beat more forceful. Premature beats are sometimes but not always associated with other arrhythmias.

Premature beats may originate from anywhere in the heart. The most common form of premature beat seen in daily practice is a premature contraction originating in the ventricle (PVC =premature ventricular contraction). Premature contractions in the atria (PAC) are also rather common.

The presence of premature beats usually is not a major concern. Premature contractions are common in normal individuals. Their presence alone does not require treatment unless they cause intolerable symptoms. Very often, a few changes in lifestyle, such as reducing stress or avoiding caffeine, will be sufficient to regulate the heartbeat. If premature ventricular beats are frequent or occur in certain patterns, they may be indicative of more serious problems. Because of these serious implications, a physician expert in arrhythmias should evaluate patients with PVC's. Often further evaluation may be indicated, but treatment may not be needed. Persons found to have no significant abnormalities of the heart normally have a very low risk of having serious problems. If other heart problems are detected, however, electrophysiology testing may be necessary.

Premature Atrial Contraction (PAC) originates within the atrial myocardium but outside the SA node. The PAC occurs before the next expected sinus discharge; it maybe conducted normally through the AV node and ventricles; or it can be partially or completely blocked. The cause of PAC is not fully known. An increased rate of premature contractions has been observed prior to the onset of atrial fibrillation and has been associated with lung and thyroid diseases.

Premature Ventricular Contractions (PVC) are the most common of the ventricular arrhythmias. They may arise from a ventricular focus with enhanced automaticity or may represent a form of reentry within the His-Purkinje system. PVC's may occur randomly or may alternate with normal beats in a regular pattern. Isolated PVC in the setting of cardiac disease (e.g. recent heart attack) can indicate increased risk of having ventricular tachycardia or fibrillation, both of which increase the risk of sudden death.

Premature Junctional (AV Nodal) beats originate near the AV node junction. In general, they do not require treatment. They may , however, be signs of drug toxicity, in which case treatment involves decreasing the drug dosage.