Effects of therapeutic concentrations of procainamide on transmembrane action potentials of normal and infarct zone Purkinje fibers and ventricular muscle cells

Journal of Cardiovascular Pharmacology
K H Dangman, D S Miura

Abstract

Procainamide is a class I antiarrhythmic drug. Most studies of the cellular electrophysiologic effects of procainamide have been done with concentrations well above the therapeutic range. We studied the effects of therapeutic concentrations (10 mg/L) of the drug on transmembrane action potentials recorded from isolated canine cardiac tissues. In normal false tendon Purkinje fibers with maximal diastolic potentials (MDPs) of -93 +/- 1 mV, procainamide decreased action potential duration (APD)-20mV and slightly prolonged APD100%. The dV/dtmax was not decreased. In normal subendocardial Purkinje fibers with MDPs of -92 +/- 1 mV, procainamide 10 mg/L significantly decreased dV/dtmax but did not affect APD-20mV. In normal muscle cells from left ventricular endocardium, procainamide 10 mg/L increased only APD100%. The effects of procainamide on partially depolarized Purkinje fibers varied. In normal subendocardial Purkinje fiber preparations superfused with 7.5 mM KCl-Tyrode's solution, the mean maximal diastolic potentials were -73 +/- 2 mV, and procainamide 10 mg/L slightly decreased action potential amplitude (APA) and increased APD-60mV. In contrast, in 24-h infarct zone Purkinje fibers with MDPs of -75 +/- 4 mV, procainamide 10 ...Continue Reading

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