Electrophysiological effects of ethmozin on sinus nodal function in patients with and without sinus node dysfunction.

The electrophysiological effects of intravenously administered ethmozin (1 mg kg-1) on sinus node function were examined in 32 patients. Based on their clinical data and the results of the initial study, patients were subdivided into group A (n = 12), those with sick sinus syndrome and sinus node recovery time (SNRT) greater than 1500 ms, and group B (n = 20), those without overt sinus node dysfunction and a normal SNRT. The mean sinus cycle length did not change significantly in either group after ethmozin . SNRT was prolonged by ethmozin in group A whereas in group B the increase of SNRT was not significant. Corrected SNRT increased after ethmozin in both subgroups but with a much more pronounced increase in group A. Sinoatrial conduction time was not significantly changed in any group. The lengthening of SNRT in the majority of patients with sick sinus syndrome implies that ethmozin might prolong post-tachycardia pauses in these patients. This drug should therefore be administered cautiously to persons with signs indicative of dysfunction of the sinus node.