ACTION DE LA BUNAFTINE SUR LA PHASE SUPERNORMALE DE L'EXCITABILITE MYOCARDIQUE

In 8 patients with a temporary pacemaker, investigations were carried out into the supranormal phase of excitability induced by Bunaftine, a derivative of ethylenediamine, which has anti-arrhythmic properties. During continuous electrocardiographic recording, and after assessment of the threshold of myocardial stimulation, the supranormal phase was shown by the occasional depolarising effect of subliminal stimulation. By examining the chronological relationship between effective subliminal stimulation and spontaneous rhythm complexes, it was possible to calculate the beginning, end and the duration of the supranormal phase. The Q-T interval, the QRS interval and cardiac frequency were also calculated. The most important factor in this investigation was the decrease, by an average of 57.3 % of the duration of the supranormal phase (p <0.001) after Bunaftine treatment. At the same time, there was found to be a lengthening of the Q-T interval by 11.8 % (p <0,001). The drug does not cause any significant changes in either the length of the QRS interval or cardiac frequency. It is therefore possible that the effect of Bunaftine on the supranormal phase is one way in which it exercises its antiarrhythmic effect.