atrial premature complex

(APC) a single ectopic atrial beat arising prematurely, manifest electrocardiographically as an abnormally shaped premature P wave, usually with a slightly increased PR interval. It occurs in normal hearts, sometimes associated with the use of stimulants, but may be associated with structural heart disease.

Atrial premature complexes that block conduction entirely in the atrioventricular (AV) node (up arrowhead) or conduct with a functional left bundle branch block (down arrowhead), or functional right bundle branch block (right arrowhead), depending on the preceding cycle length and coupling interval of the premature complex.