We investigated the effects of
diltiazem cardioplegia on myocardial function and
infarct size in the region of the left anterior descending artery after acute occlusion and reperfusion during
cardiopulmonary bypass. Sheep (30 kg) were subjected to 1 hour of regional
myocardial ischemia by occlusion of the left anterior descending artery and assigned to a control (n = 8) or experimental group (n = 5). Control animals were placed on
cardiopulmonary bypass and the heart arrested with
potassium cardioplegia. The left anterior descending artery was released and two additional doses of 100 ml of
cardioplegic solution were infused during the total cross-clamp time of 30 minutes. The animals were then weaned from bypass after 1 hour and beating, working reperfusion maintained for an additional 4 hours. The experimental group followed the same protocol except that the
cardioplegic solution contained
diltiazem (1.4 mg/L). Segmental myocardial function was determined by pairs of ultrasonic crystals in the area at risk, control segment, and minor axis. Global contractility was determined from maximum derivative of left ventricular pressure and cardiac output. The area at risk was determined by injecting
monastral blue dye into the left atrium with the left anterior descending artery briefly reoccluded, and the area of
necrosis was determined by measuring with a planimeter non-
triphenyltetrazolium chloride stained areas in the sectioned left ventricle. After 5 hours of reperfusion, not only did the
diltiazem group demonstrate better global contractility as defined by the derivative of left ventricular pressure (1853 +/- 292 versus 979 +/- 191, p = 0.05) but, in addition, the systolic shortening in the ischemic area improved significantly when compared with the control group (9.4 +/- 4 versus 2.13 +/- 0.77, p = 0.05). The group receiving
diltiazem cardioplegia had an area of
necrosis to area at risk ratio of 31.4% +/- 3%, which was significantly better than this ratio in the control group of 60.75% +/- 7% (p = 0.01).
Diltiazem cardioplegia results in improved global and segmental contractility and limits the
infarct size after occlusion of the left anterior descending artery and surgical reperfusion.