Effect of tiapamil on canine myocardial infarct size.

Limitation of infarct size, using the calcium entry blocker, tiapamil (T), was evaluated in a group of eight dogs during acute and chronic (8 days) myocardial infarction. An equal number of dogs served as the control (C) group. A closed-chest model was used to produce the thrombus by placing a helically-shaped copper wire in the left anterior descending artery (LAD) by catheter technique, under x-ray visualization. Necrotic tissue in serial transventricular sections was delineated by triphenyl tetrazolium chloride and was measured by computer technique, using an IBM-PC interfaced with a digitizing pad, 8 days following occlusion. The mean total amount of necrosis in T animals (9.5%) was significantly less (p less than 0.05) than found in C dogs (19.7%), or a difference of 48% between the two groups. A number of significant (p less than 0.05 to p less than 0.001) between-group comparisons, at the same condition, were found for various hemodynamic, creatine phosphokinase (CPK), and precordial ST segment, Q and QS wave variables followed before and at 1, 3, and 6 hours after occlusion, as well as on the second and eighth day. The results of this study strongly suggest that tiapamil has a protective effect on myocardial function, following thrombotic occlusion of the LAD, as well as limiting the resulting infarct size.