Electrophysiologic diagnosis of patients with sinus node dysfunction: with special reference to a modified method for calculating sinoatrial conduction time

The diagnostic value of maximum corrected sinus node recovery time (CSNRT) and sinoatrial conduction time (SACT) was assessed in 15 patients with clinical evidence of sinus node (SN) dysfunction and 16 control subjects. The SACT was calculated by a modified method using only those sinus cycles with A1-A1 intervals falling within one standard deviation of the mean. We also obtained a maximum SACT and a ratio of maximum/mean SACT. We found that the maximum/mean SACT ratio being useful for identifying patients with sinus arrest or sinoatrial block. Abnormal value of the ratio (greater than or equal to 1.85) was also more frequently observed in patients with syncope or dizzy spells than those without (55.6% vs. 33.3%). By applying mean SACT and maximum/mean SACT ratio, calculated by the modified method, together with maximum CSNRT, all patients with SN dysfunction could be completely isolated from the normal subjects.