ISSN:
1432-1912
Keywords:
Cardiac muscle
;
Antiarrhythmic drugs
;
Electrophysiology
;
Recovery of V maX
;
Action potential duration
;
Rate-dependent block
;
Sodium channels
;
Potassium channels
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract The cellular electrophysiological effects of dridocainide (EGIS-3966), a novel class I antiarrhythmic agent, was studied using conventional microelectrode techniques in canine cardiac Purkinje fibres and papillary muscle preparations obtained from humans and guinea-pigs. In each preparation, dridocainide (0.6–2 μmol/l) decreased the maximum velocity of action potential upstroke (Vmax) in a frequency-dependent manner, although marked differences were observed in its effects in Purkinje fibre and ventricular muscle preparations. In canine Purkinje fibres, action potential duration measured at 50% and 90% of repolarization was decreased, while action potential duration measured at 10% of repolarization was increased by dridocainide. In addition, the plateau of the action potential was depressed by the drug. These changes in action potential configuration were not observed in guinea pig or human papillary muscles. The offset kinetics of the dridocainide-induced V max block were different in Purkinje fibres and in ventricular muscle: the slow time constant of recovery of V max was estimated to be 2.5 s in dog Purkinje fibre and 5–6 s in human and guinea-pig papillary muscle. In guinea-pig papillary muscle, the rate of onset of the V max block was 0.15 and 0.2 per action potential in the presence of 0.6 and 2 μmol/l dridocainide, respectively. Dridocainide also decreased the force of contraction in this preparation. On the basis of the present results, dridocainide appears to posess mixed class LC and LA properties, with LC predominance in human and guinea-pig ventricular muscle. Present results also indicate that results of conventional classification of class I drugs may depend on the parameters chosen, as well as on the preparation selected.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00169386
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