Electrophysiologic effects of intravenous dipyridamole.

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 less than 0.001), sinuatrial conduction time by 15 per cent (P less than 0.01), maximal sinus node recovery time by 21 per cent (P less than 0.001), atrial and atrioventricular nodal effective refractory period by 8 and by 11 per cent, respectively (both P less than 0.01), ventricular effective refractory period by 4 per cent (P less than 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 less than 0.01). After dipyridamole, the PA interval increased by 16 per cent (P less than 0.001), the AH interval by 11 per cent (P less than 0.01), and the corrected QT interval by 5 per cent (P less than 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 less than 0.001), paced cycle length to atrioventricular nodal Wenckebach and atrioventricular nodal Mobitz type II block both by 8 per cent (P less than 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.(ABSTRACT TRUNCATED AT 250 WORDS)