Diltiazem ameliorates contractile dysfunction without shortening of action potential duration in ischemic heart of anesthetized dogs.

The purpose of the following experiment was to determine whether amelioration of myocardial contractile dysfunction by diltiazem is mediated by shortening of monophasic action potential duration (MAPD) during myocardial ischemia in anesthetized dogs. Diltiazem improved regional contraction during reperfusion after 10-min occlusion. The shortening of MAPD and increase in [K+]e were blunted by treatment with diltiazem. These results suggest that shortening of action potential duration during myocardial ischemia is unlikely to be a reason for the amelioration of contractile dysfunction.