Concealed quadrigeminy and quintageminy

Electrocardiographic rhythm strips were analyzed from three patients who had frequent unifocal extrasystoles. Parasystole was excluded in all three cases. Analysis of the distributions of the numbers (S) of conducted sinus beats between extrasystoles revealed that the distributions conformed to two variants of concealed quadrigeminy (namely, the "S = 4n" and "S = 4n - 2" variants) and to one variant of concealed quintageminy (namely, the "S = 5n - 2" variant). The binomial theorem was used to test the likelihoods that these patterns of distribution of extrasystoles could occur on the basis of chance alone; the probabilities were all extremely small.