EFFECTS OF ANTIARRHYTHMIC DRUGS ON SIGNAL -AVERAGED ELECTROCARDIOGRAMIN PATIENTS WITH VENTRICULAR-TACHYCARDIA - RELATION TO RESULTS OF ELECTROPHYSIOLOGICAL STUDIES

Effects of class IA, IC and III antiarrhythmic drugs as monotherapy or in combinations on dynamics of signal-averaged ECG and ventricular la te potentials were studied in 26 patients with ventricular tachycardia , Data obtained were related to results of 96 electrophysiologic studi es performed in these patients. At control electrophysiological invest igation sustained ventricular tachycardia was induced in 19 (73%) and was not-in 7 patients. Before treatment ventricular late potentials we re recorded in 79% of patients with inducible and in 29% of patients w ith nonunducible ventricular tachycardia. Quantitative analysis reveal ed significant differences between parameters of signal-averaged ECG i n both groups, All the antiarrhythmic drugs led to worsening of parame ters of signal-averaged EGG: to increase in duration of filtered QRS c omplex (fQRSD) and of low amplitude signals in the terminal portion of the QRS complex (DLAS<40 V), to reduction of root-mean-square voltage of last 40 ms of the QRS complex, Changes of fQRSD caused by class IC antiarrhythmic drugs and of fQRSD and DLAS<40 V observed during combi ned use of amiodarone and class I drugs were statistically significant . Suppression of inducibility of sustained ventricular tachycardia by antiarrhythmic drugs observed in 18 of 63 tests (30%) was associated w ith distinct tendency to more pronounced change in parameters of signa l-averaged ECG and with appearance of ''new'' late potential, Degree o f changes of parameters of signal-averaged ECG is believed to be relat ed to special characteristics of effects produced by an antiarrthmic d rug on velocity of impulse conduction in the myocardium, Thus signal-a veraged ECG may be useful for elucidation of mechanisms of action of d ifferent subgroups of antiarrhythmic drugs.