Effect of isoetharine on cardiac conduction in man.

The effects of isoetharine on the His bundle electrogram were studied in 10 patients with heart disease. Recordings were made at varied heart rates using atrial pacing. Isoetharine significantly reduced the AH interval with atrial pacing, but it had no effect on the HV interval. Second degree heart block occurred at higher pacing rates after isoetharine treatment as compared to the control state. The heart rate and blood pressure showed no significant change after isoetharine. The functional and effective refractory period were measured with the use of the extra-stimulus technique. The functional refractory period of the AV node, as well as the effective refractory period of the atrium, significantly decreased after isoetharine. Thus, isoetharine can improve conduction through the atrioventricular node. The drug does have a cardiac effect as measured by its action on the human conduction system.