Electrophysiological features of one to two atrioventricular conduction in dual AV node pathway

Objective To summarize the electrophysiological features of one to two atrioventricular conduction in dual AV node pathway. Methods Analyzing the conditions in which 1∶2 atrioventricular conduction occurred and measuring the basic AH, HV, atrial effective refractory period, effective refractory period of fast pathway of atrioventricular node and difference of conduction time between fast and slow pathways in the cases with 1∶2 atrioventricular conduction and compare them with those cases without 1∶2 atrioventricular conduction. Results Basic AH was 50-80 (60 9±7 0)ms, HV was 35-40 (38 6±2 3) ms; atrial effective refractory period was 130-240 (194 5±31 4) ms in 11cases with 1∶2 atrioventricular conduction, there were no significant differences as compared to those cases without 1∶2 atrioventricular conduction; the effective refractory periods of fast pathway of atrioventricular node were less than 220 ms in seven patients and were 400, 380, 320, 280, 240 ms, respectively, in remainders. The difference of conduction time between fast and slow pathways was 300-740 (499 0±121 8) ms, which was significantly longer than that of controls and also longer than the effective refractory period of fast pathway in the same group. One to two atrioventricular conduction could be induced by atrial premature beat, atrial extrastimulus, atrial burst pacing, sinus beat, ventricular premature stimulus and also occurred during atrioventricular node reentrant tachycardias in multiple atrioventricular node pathway. Conclusion The prerequisite for 1∶2 atrioventricular conduction is that the difference of conduction time between fast and slow pathways is longer than the effective refractory period of distal common pathway of atrioventricular node.