Studies on the calcium antagonistic action of tetrandrine: XI. Effects of tetrandrine and calcium chloride on the impedance cardiogram of anesthetized canines

Abstract

Tetrandrine (Tet) 10 mg/kg or verapamil (Ver) 0.4 mg/kg i.v. decreased cardiac contractility as shown by the lowering of dZ/dt_max, prolongation of Q-Z interval and decrease of Heather index in anesthetized dogs. The pump function parameters of the heart: cardiac output, cardiac index, stroke volume, stroke index and time tension index were reduced concomitantly. Since both drugs decreased heart rate, total peripheral resistance and time tension index, the oxygen consumption of the heart might be reduced accordingly.

The fact that the effects of Tet and Ver on the heart rerformance are very similar and can all be reversed by calcium chloride gives further support to the speculation that Tet may be a slow channel blocker.

Keywords

tetrandrine / verapamil / Q-Z interval / impedance cardiogram