Sustained limitation of myocardial necrosis 24 hours after coronary artery occlusion: verapamil infusion in dogs with small myocardial infarcts.

Studies were undertaken to ascertain whether verapamil infusion affords a sustained limitation of myocardial injury in the dog after a 24-hour period of coronary artery occlusion. Regional myocardial ischemia was induced by an embolization procedure which did not involve thoracotomy. Immediately after embolization radioactive microspheres were administered intraventricularly to define any area of myocardial underperfusion (zone at risk of infarction). Verapamil (0.005 mg/kg/min) was then administered and maintained for 24 hours during which time the dogs were allowed to recover from anesthesia. The control group received a corresponding infusion of saline solution. After 24 hours the dogs were killed and transverse myocardial sections (3 mm) were prepared. The resulting area of necrosis was visualized by tetrazolium staining, and risk zones were visualized by autoradiography. In the control heart, 62 +/- 7% of the zone at risk deteriorated to necrotic tissue, whereas in the verapamil-treated group only 18 +/- 4% of the tissue in the zone at risk became necrotic. Verapamil appeared to exert a significant (p less than 0.001) tissue-sparing effect that was sustained for at least 24 hours after the onset of ischemia.