Concealed extrasystoles due to Wenckebach conduction delay within the reentry loop.

Long electrocardiographic strips were analyzed from an aged patient whose heart rhythm had periods of unifocal ventricular extrasystoles with fixed coupling intervals. Periods of gradual prolongation of the coupling interval finally led to omission of a ventricular premature beat. This sequence was repetitive and is considered to be the results of reentrant extrasystoles with a 3:2 Wenckebach type of conduction delay within the reentry loop. The mechanism of concealed conduction due to overlong propagation within the reentry loop is discussed.