In-vitro and in-vivo electrophysiologic effects of encainide

✍ Scribed by Christian Libersa; Jacques Caron; René Rouet

• Publisher: Springer US
• Year: 1990
• Tongue: English
• Weight: 370 KB
• Volume: 4
• Category: Article
• ISSN: 0920-3206
• DOI: 10.1007/bf00357032

✦ Synopsis

The intracellular electrophysiologic effects of encainide (E) and its main metabolite, O-desmethyl-encainide (ODE), were studied in guinea-pig papillary muscle preparations and related to the in-vivo electrophysiologic effects observed after intravenous (IV) infusion of E in 11 patients undergoing electrophysiologic study (EPS).

At equipotent concentrations of E and ODE, frequencydependent reductions in Vm~ studied at pacing rates of 30-180 beats/min ranged from -11.5% to -53%, with maximum reductions of -53% and -47%, respectively at the highest frequency. The kinetics of onset of use-dependent Vm~ reduction were slower for ODE than for E at each studied pacing rate. The kinetics of total recovery from use-dependent block were still slower (120 seconds for E and 300 seconds for ODE at a 90 beats/min pacing rate).

These in-vitro electrophysiologic data could explain the marked alterations in intraventricular and atrioventricular conduction observed in humans 60 minutes after IV administration of 1 mg/kg of E over a 15-minute period. The QRS, PA, AH, and HV intervals were significantly increased (p < 0.01) and the Wenckebach cycle length was increased by 8% (p < 0.05). Blood pressure, RR, QT, CSNRT, ESACT, ERP, and FRP did not vary significantly. The HV interval was already increased 2 minutes after drug administration, while All was not increased until 15 minutes after drug administration. There was a positive correlation between the increase of the All interval and the blood level of ODE.