Alvidas Lubas

Institute of Cardiology, Kaunas University of Medicine

Key words: antiarrhythmic drugs, antifibrillatory activity, programmed electrical stimulation.

Summary. This article presents data about antifibrillatory effectiveness of certain antiarrhythmic drugs class I, II, III [intravenous lidocaine – IB (7.8 mg/kg), propafenone – IC (2 mg/kg), atenolol – II (2 mg/kg), amiodarone (5 mg/kg), bretylium tosylate (6–10 mg/kg) and quaternidine – III (2.15 mg/kg)], which were tested using the method of programmed electrical stimulation. Experiments were carried out on cats, anaesthetized with urethane (1.2 g/kg i/p), curarised with d-tubocurarine (0.4 mg/kg i/v) and subdued on artificial respiration.

It was established that tested antiarrhythmic drugs, except b1-selective adrenoblocker atenolol and propafenone, demonstrate distinctively intense antifibrillatory properties. The most active is amiodarone, which increases the ventricular fibrillation threshold almost three fold (from 12.8 to 30.09 mA), bretylium tosylate – about – 2.5 fold (from 10.43 to 24.65 mA). Lidocaine and quaternidine show almost equal action – ventricular threshold they increase about two fold, from 11.78 to 20.64 mA and from 12.3 to 20.92 mA respectively. They decrease maximal driving frequency, increase duration effective refractory period of the heart. Amiodarone, bretylium tosylate, lidocaine and quaternidine increase diastolic excitation threshold and diapason of not dangerous to the heart stimulation currents. Propafenone inconsiderably increases only ventricular fibrillation threshold from 12 to 16.18 mA (1.3 fold). Atenolol in this case is not active. Duration time of antifibrillatory efficacy of amiodarone is more than 2.5, lidocaine – 1–1.5, bretylium tosylate and quaternidine about 2 hours.