Electrophysiologic effects of intravenous dipyridamole

Abstract

We evaluated the electrophysiologic effects of dipyridamole given intravenously to 24 patients during intracardiac electrophysiologic study. Electrophysiologic parameters were measured before and 5 minutes following infusion of 0.5 mg/kg of dipyridamole. The drug significantly shortened the sinus cycle length by 26 per cent ( P < 0.001), sinuatrial conduction time by 15 per cent ( P < 0.01), maximal sinus node recovery time by 21 per cent ( P < 0.001), atrial and atrioventricular nodal effective refractory period by 8 and by 11 per cent, respectively (both P < 0.01), ventricular effective refractory period by 4 per cent ( P < 0.001), paced cycle length to atrioventricular nodal Mobitz type II block by 5 per cent ( P = 0.046), and QT interval during sinus rhythm by 10 per cent ( P < 0.01). After dipyridamole, the PA interval increased by 16 per cent ( P < 0.001), the AH interval by 11 per cent ( P < 0.01), and the corrected QT interval by 5 per cent ( P < 0.01). During retrograde conduction we observed a shortening of the ventriculoatrial interval by 6 per cent ( P = 0.036), retrograde atrioventricular nodal effective refractory period by 5 per cent ( P < 0.001), paced cycle length to atrioventricular nodal Wenckebach and atrioventricular nodal Mobitz type II block both by 8 per cent ( P < 0.01). We conclude that intravenous dipyridamole increases sinus node automaticity and reduces atrial, atrioventricular nodal and ventricular refractory periods, prolongs intra-atrial and atrioventricular nodal conduction, but does not produce any changes in His-Purkinje system conduction times. Paced cycle length to atrioventricular nodal Wenckebach and Mobitz type II block decreased after dipyridamole during antegrade as well as retrograde conduction.