ISSN:
1573-7241
Keywords:
encainide
;
O-desmethyl-encainide
;
electrophysiologic studies
;
conduction intervals
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary 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, frequency-dependent reductions in Vmax 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 Vmax 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 AH was not increased until 15 minutes after drug administration. There was a positive correlation between the increase of the AH interval and the blood level of ODE.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00357032
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