Electrocardiological profile and proarrhythmic effects of quinidine, verapamil and their combination: a mapping study.

Quinidine and verapamil are widely used as antiarrhythmic agents and their combination is often used in the treatment of supraventricular tachycardia. This study was undertaken to clarify, whether these drugs exert proarrhythmic effects on the ventricles in therapeutic concentrations and whether possible arrhythmogenic effects might be enhanced by combination. Isolated rabbit hearts perfused according to the Langendorff technique were treated with increasing concentrations of quinidine (0.05 to 3.5 microM) or verapamil (5 to 50 nM) or of their combination (70:1 or 10:1, quinidine:verapamil) corresponding to common low, medium and high free therapeutic concentrations. The epicardial activation process was measured using a computer assisted mapping system for unipolar multichannel recording (256 channels simultaneously). Both substances prolonged the atrioventricular conduction time PQ. This effect was even more pronounced if the 70:1 combination was administered. The activation pattern was altered by both drugs and their combination to the same extent as became obvious from analysis of local activation vectors and of localisation of breakthroughpoints of epicardial activation for heart beats under control conditions and under drug treatment. The epicardial potential durations were prolonged by quinidine and to the same degree by the combinations, but not by verapamil alone. The total activation time was prolonged under the influence of quinidine and if the 70:1 combination was given. Both substances exerted a negative inotropic effect which was enhanced in an additive manner if both drugs were combined. In parallel the coronary flow was diminished.(ABSTRACT TRUNCATED AT 250 WORDS)