Alteration of ventricular fibrillation by flecainide, verapamil, and sotalol - An experimental study

Background-The purpose of this study was to determine whether the myocardia l electrophysiological properties are useful for predicting changes in the ventricular fibrillatory pattern. Methods and Results-Thirty-two Langendorff-perfused rabbit hearts were used to record ventricular Fibrillatory activity with an epicardial multiple el ectrode. Under control conditions and after flecainide, verapamil, or d,l-s otalol, the dominant frequency (FrD), type of activation maps, conduction v elocity, functional refractory period, and wavelength (WL) of excitation we re determined during ventricular fibrillation (VF). Flecainide (1.9+/-0.3 v ersus 2.4+/-0.6 cm, P<0.05) and sotalol (2.1+/-0.3 versus 2.5+/-0.5 cm, P<0 .05) prolonged WL and diminished FrD during VF, whereas verapamil (2.0+/-0. 2 versus 1.7+/-0.2 cm, P<0.001) shortened WL and increased FrD. Simple line ar regression revealed an inverse relation between FrD and the functional r efractory period (r=0.66, P<0.0001), a direct relation with respect to cond uction velocity (r=0.33, P<0.01), and an inverse relation with respect to W L estimated during VF (r=0.49, P<0.0001). By stepwise multiple regression. the functional refractory periods were the only predictors of Fro. Flecaini de and sotalol increased the circuit size of the reentrant activations, whe reas verapamil decreased it. The 3 drugs significantly reduced the percenta ges of more complex activation maps during VF. Conclusions-The activation frequency is inversely related to WL during VF, although a closer relation is observed with the functional refractory perio d. Despite the diverging effects of verapamil versus flecainide and sotalol on the activation frequency, WL, and size of the reentrant circuits, all 3 drugs reduce activation pattern complexity during VF.