[Variant gap phenomenon in A-V conduction]

In 361 consecutive patients 4 with variant gap phenomenon (VGP) underwent intracardiac electrophysiological studies. The premature atrial response initially delayed in His-Purkinje system (HPS) which had a long relative refractory period (RRP), and H-V interval was prolonged. However, as atrial responses were more premature, the atrioventricular node (AVN) showed RRP and slowed down the conduction, that made HPS get rid of RRP before the response arriving. Thus the conduction resumed, and H-V interval became normal. It was different from the classic gap phenomenon. We call it variant gap phenomenon.