ELECTRICAL STIMULATION TO ESTIMATE DEGREE OF DIGITALIZATION .2. EXPERIMENTAL STUDIES

In the animal digitalized with either ouabain or acetyl strophanthidin electrical stimulation of the heart results in an unusual response. After intravenous infusion of 50 per cent of the toxic dose of digitalis, a threshold stimulus provoked a repetitive ventricular response. In the nondigitalized animal, even massive unipolar diastolic stimuli were followed by only single responses. The most sensitive part of the cardiac cycle for repetitive ventricular response followed immediately after inscription of the T wave. The initial response was a coupled extrasystole; with advancing degrees of digitalization trains of extrasystoles and paroxysms of ventricular tachycardia ensued. As toxicity was approached, the zone for electrically induced repetitive ventricular response extended throughout two thirds of the diastolic interval. The method of unipolar diastolic stimulation of the myocardium may permit estimation of the degree of digitalization in man. © 1968.