Treatment with diltiazem preoperatively in open heart surgery for myocardial protection: experimental studies in dogs with chronic healed myocardial infarction

Calcium antagonists have become important in open heart surgery because of their effects on myocardial protection and cardioplegia. We evaluated the effect of pretreatment with the calcium antagonist diltiazem for myocardial protection in dogs with experimentally induced, chronic, healed myocardial infarction in a double-blind randomized study. One group consisted of 5 dogs treated with diltiazem (10 mg/kg bodyweight) for 7 days preoperatively, while a second group of 4 dogs were treated with placebo. All animals then underwent hypothermic, ischemic cardiac arrest (90 min) with extracorporeal circulation (ECC), followed by 30 min of reperfusion. Hemodynamic parameters were measured before and after ECC. An EKG was recorded during the entire procedure. The myocardium was studied by light microscopy for fresh necroses. The old, experimentally induced infarction scars were quantified by a new method that was developed for planimetry of the histological specimens. The diltiazem group compared with the placebo group showed myocardial cell necroses to a smaller extent. The hemodynamic studies supported the contention that diltiazem given preoperatively has a myocardial protective effect. These results encourage further studies on the use of diltiazem preoperatively for myocardial protection.