Sinus node electrogram recording in complete atrioventricular block

Surface electrocardiogram (ECG), sinus node electrogram (SNE), His bundle electrogram (HBE), and intracardiac electrogram of high right atrium (HRA) were recorded synchronously in 11 of the 14 consecutive cases with complete atrioventricular block (CAVB). SNE showed the presence of a pre-P wave that preceded in all the P wave on the ECG and had no relationship to QRS complex or TU repolarization. This confirmed that the pre-P wave arose from the sinus node. Direct sinoatrial conduction time (SACTd) in nine cases was within the normal range (less than 120 msec). SACTd in another two cases was prolonged to 185 msec and 210 msec, respectively, suggesting their abnormal sinus node conduction.