Supraventricular premature beats represent premature activation of the atria from a site other than the sinus node and can originate from the atria or the atrioventricular node (called junctional premature beats), though the vast majority are atrial in origin. Atrial premature beats (APBs), also referred to as atrial premature complexes, premature atrial beats, premature atrial complexes, or atrial extrasystoles, are triggered from the atrial myocardium in a variety of situations and occur in a broad spectrum of the population. This includes patients without structural heart disease and those with any form of cardiac disease, independent of severity.
The prevalence, mechanisms, clinical manifestations, diagnosis, and treatment of APBs will be presented here. A discussion of ventricular premature beats is presented separately. (See "Ventricular premature beats".)
APBs are fairly ubiquitous, occurring commonly in both young and elderly subjects and in those with and without significant heart disease. The prevalence of APBs is highly dependent upon the technique used for evaluation. APBs are less commonly seen on standard 10-second electrocardiogram compared with 24-hour or longer duration Holter monitoring. In a cross-sectional analysis of 1742 Swiss adults (50 years of age or older) from the general population who underwent Holter monitoring for 24 hours, 99 percent had at least one APB during the monitoring period . In this Swiss cohort, the frequency of APBs steadily increased with age, with rates of 0.8, 1.4, and 2.6 APBs per hour among participants aged 50 to 55 years, 60 to 65 years, and 70 or more years, respectively . Similar findings of greater APB frequency with advancing age have been reported in other cohorts as well [2-4].
The presence and frequency of APBs is dependent upon the presence of structural heart disease. APBs are particularly frequent in patients with mitral valve disease and in those with left ventricular dysfunction regardless of etiology. However, the high prevalence of APBs in the normal population makes such associations uncertain. (See 'Etiology' below.)
The wide range in the reported prevalence of APBs in different populations may be related to the day-to-day variability in their prevalence and frequency. Circadian variation in the frequency of APBs may also occur, but there is significant interpatient variation. Although this has not been specifically studied, it is reasonable to assume that the variability is similar to that reported for ventricular premature depolarizations [5,6]. (See "Ventricular premature beats".)