The class III antiarrhythmic effect of sotalol exerts a reverse use-dependent positive inotropic effect in the intact canine heart.
OBJECTIVES: We sought to study the rate related effects of sotalol on myocardial contractility and to test the hypothesis that the class III antiarrhythmic effect of sotalol has a reverse use-dependent positive inotropic effect in the intact heart. BACKGROUND: Antiarrhythmic drugs exert significant negative inotropic effects. Sotalol, a beta-adrenergic blocking agent with class III antiarrhythmic properties, may augment contractility by virtue of its ability to prolong the action potential duration (APD). METHODS: In 10 anesthetized dogs, measurements of left ventricle (LV) peak (+)dP/dt and simultaneous endocardial action potentials were made during baseline conditions and after sequential administration of esmolol and sotalol. In addition, electrical and mechanical restitution curves were constructed at a basic pacing cycle length of 600 ms by introducing a test pulse of altered cycle length ranging from 200 ms to 2,000 ms. RESULTS: In the steady state pacing experiments, sotalol prolonged the APD in a reverse use-dependent manner; such an effect was not seen with esmolol. At cycle lengths exceeding 400 ms, LV (+)dP/dt was significantly higher with sotalol than it was with esmolol. There was a direct relation between APD and LV (+)dP/dt with sotalol (r = 0.46, p < 0.001), but there was no significant relation between APD and LV (+)dP/dt with esmolol (r = 0.27, p = NS). Results in the single beat (restitution) studies were qualitatively similar to the steady state results; APD (at cycle length >400 ms) and LV (+)dP/dt (at cycle length >600 ms) were significantly higher with sotalol than they were with esmolol. CONCLUSIONS: The reverse use-dependent prolongation of APD by sotalol is associated with a positive inotropic effect.[1]References
- The class III antiarrhythmic effect of sotalol exerts a reverse use-dependent positive inotropic effect in the intact canine heart. Peralta, A.O., John, R.M., Gaasch, W.H., Taggart, P.I., Martin, D.T., Venditti, F.J. J. Am. Coll. Cardiol. (2000) [Pubmed]
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