Sinoatrial conduction time in patients with atrioventricular block

In 20 patients with atrioventricular (A-V) block, sinoatrial conduction time (SACT) was measured in order to established to incidence of sinoatrial conduction defects. 10 patients had complete A-V block, 5 patients second-degree A-V block type 1, 2 patients second-degree A-V block type II, nd 3 patients first-degree A-V block. Prolonged bidirectional SACT was found in 8 cases (40%). The mean value (+/- SD) of SACT was 206 +/- 69 ms. In comparison with SACT in a group of 11 patients without symptoms and signs of sinus node disorder (mean value 156 +/- 25 ms) the difference was significant (p less than 0.05). On the other side, the values of SACT were shorter in patients with A-V block than in 13 patients with sick sinus syndrome (mean value 311 +/- 82 ms); the difference was statistically significant (p less than 0.001). The study shows that impairment of sinoatrial conduction frequently coexists with A-V conduction defects.