The feasibility of measuring the extent of hypoperfused myocardium and the
infarct size was examined in rat hearts after occlusion of the left coronary artery. The extent of hypoperfused myocardium was examined by autoradiography and after perfusion with fluorescent
microspheres. Both methods appeared unreliable in this model.
Triphenyltetrazolium chloride (TTC) staining, however, provided a distinct demarcation line between viable myocardium, which was stained red, and the necrotic myocardium, consistent with the ultrastructural border between normal and severely damaged myocytes 5 h after
coronary occlusion. TTC staining gives the best demarcation of ischemic tissues. In
verapamil-treated rats, there was an apparent reduction in
infarct size as compared with untreated rats; 20% reduction in
infarct size 5 h after
coronary occlusion and 12% reduction after 24 h. There was, however, a large postoperative mortality among the
verapamil-treated rats. These problems, and the nonuniform
infarct size in rats, may in part explain why
infarct size limitation by
verapamil has been reported from rat experiments, but not from clinical trials.