MYOCARDIAL INFARCTION UNMASKED BY AN UNUSUAL ARRHYTHMIA

A case is presented of second degree sinoatrial block with Wenckebach periods, and a rate-conditioned left bundle branch block masking an acute anteroseptal myocardial infarction which is revealed in the normally conducted beats occurring in the pauses caused by the second degree sinoatrial block. The mechanisms underlying this unusual tracing are discussed.