[A case of intermittent ventricular pre-excitation syndrome with a Mahaim fiber].

A 61 year-old woman with intermittent ventricular pre-excitation syndrome using a Mahaim fiber was reported. The electrocardiogram showed QRS-complex with small delta wave (100 msec in QRS width) or without small delta wave (80 msec in QRS width). On electrophysiological study, during sinus rhythm, A-H interval was 100 msec. H-V intervals were 25 msec in QRS-complex with small delta wave and 45 msec in QRS-complex without small delta wave. From these findings, it was considered that the small delta wave was produced by a Mahaim fiber.