Supraventricular premature beats can originate from the atria (called atrial premature beats/complexes or premature atrial beats/complexes) or the atrioventricular node (called junctional premature beats/complexes or premature junctional beats/complexes). This topic will review the major clinical issues related to these abnormal beats.
ATRIAL PREMATURE BEATS
An atrial premature beat (APB), also known as an atrial premature depolarization (APD), atrial premature complex (APC), premature atrial beat (PAB), or premature atrial complex (PAC), is a premature activation of the atria arising from a site other than the sinus node. They are observed on the surface electrocardiogram as a P wave that occurs relatively early in the cardiac cycle (ie, prematurely before the next sinus P wave should occur) and has a different morphology from the sinus P wave. Often the PR interval is different from that during sinus rhythm; it may be longer or shorter, depending upon the site of origin of the APB. (See "ECG tutorial: Atrial and atrioventricular nodal (supraventricular) arrhythmias", section on 'Premature atrial contractions'.)
APBs may be asymptomatic or cause symptoms such as a sensation of "skipping" or palpitations. APBs are often single and isolated, but may be frequent and may occur in a bigeminal pattern. Although APBs have a wide array of manifestations, they are not life-threatening by themselves. In predisposed individuals, APBs may initiate supraventricular [1,2] and, less commonly, ventricular arrhythmias [3,4]. Atrial fibrillation (AF) is the most common arrhythmia induced by APBs, particularly those that originate around the pulmonary vein . The presence and frequency of APBs has been shown to predict the development of AF after cardiac surgery and the recurrence of AF after cardioversion [6,7]. (See "The electrocardiogram in atrial fibrillation", section on 'Atrial activity'.)
Prevalence and significance of APBs — APBs occur commonly in both young and elderly subjects and in those with and without significant heart disease; they should not be considered an abnormal finding . The prevalence of APBs is highly dependent upon the technique used for evaluation; 24-hour Holter monitoring is most accurate and is the preferred modality.
The presence and frequency of APBs is dependent upon the presence of structural heart disease. They are particularly frequent in patients with mitral valve disease and in those with left ventricular dysfunction regardless of etiology. APBs also occur more frequently in association with noncardiac medical conditions such as acute and chronic pulmonary disease, chronic renal failure, and neurologic disorders. (See 'Etiology of APBs' below.) However, the high prevalence of APBs in the normal population makes such associations uncertain.