EFFECTS OF APRINDINE ON ELECTROPHYSIOLOGICAL PROPERTIES OF THE ATRIALMUSCLE IN MAN

The effects of aprindine on atrial vulnerability were studied in 11 pa tients; 9 with paroxysmal atrial fibrillation (PAF), and 2 with Wolff- Parkinson-White syndrome, aged 19 to 69 (55.9+/-16.5; mean+/-SD). Befo re and 10 min after the intravenous injection of aprindine (1.5 mg/kg) , programmed extrastimulation was performed from the right atrial appe ndage. Atrial vulnerability was assessed by evaluating the repetitive atrial firing zone (RAFZ), conduction delay zone (CDZ), maximum conduc tion delay (Max. CD) and fragmented atrial activity zone (FAAZ). After the injection, the duration of the P wave and QTc interval was signif icantly prolonged without any change in blood pressure or heart rate. RAF was observed in 8 patients under control conditions. However, afte r the injection of aprindine, the RAFZ completely disappeared in 2 pat ients, was narrowed in 4, and became wider in 1. AF was induced in the remaining patient. The zone significantly reduced (p<0.01) without an y change in CDZ or Max. CD. While FAA was observed in 5 patients under control conditions, it completely disappeared in 2 patients, was narr owed in 1, and did not change in the remaining 7 after the injection o f aprindine. In patients whose RAFZ narrowed after administration of a prindine, the wavelength, as determined from the atrial effective refr actory period and conduction velocity, was augmented. These results in dicate that aprindine suppresses atrial vulnerability with an augmenta tion of the wavelength. However aprindine exaggerated atrial vulnerabi lity in some patients, such that atrial fibrillation was induced.