The protective effect of diltiazem, a calcium channel blocker on myocardial ischemia during open heart surgery--an analysis of electrolyte changes in myocardial cells

This study was designed to analyze the electrolytes changes in myocardial cells, and to clarify the effect of diltiazem, a calcium channel blocker on myocardial ischemia during open heart surgery. Thirty patients who underwent open heart surgery using cold glucose-insulin-potassium (GIK) cardioplegic solution were divided into following three groups. C group: diltiazem was not administered. CD group: cardioplegic solution containing diltiazem 7.5 mg/L was used. DP group: diltiazem 1.5 micrograms/kg/min was given continuously by intravenous administration from the day before operation to the day after operation. Atrial wall biopsies were performed before aortic cross clamp (non-ischemic status), after 60 minutes' ischemia, and 5 minutes after releasing aortic cross clamp (reperfusion). The specimens were freshly frozen and measured for various electrolytes by means of X-ray microprobe analysis. In C group, potassium level decreased during both ischemia and reperfusion, while calcium level increased during ischemia and significantly increased during reperfusion period. In DC and DP groups, calcium accumulation during reperfusion was suppressed, and potassium level which had been lowered during ischemia recovered to the level of non-ischemic status during reperfusion. Sodium and chlorine showed an increase during ischemia in each group. However, sodium accumulation in DC and DP groups tended to recover during reperfusion. DP and DC groups were considered to be superior to C group in terms of cardiac index and left ventricular work. This may be due to afterload reduction as evidenced by low systemic vascular resistance. Intracellular electrolytes environment during reperfusion and hemodynamics during early postoperative periods were excellent in DP group. CPK-MB was significantly lower in both CD and DP groups than in C group. These data suggested that diltiazem could suppress intracellular calcium accumulation and keep homeostasis of sodium-potassium pump mechanism in membrane during reperfusion. It is concluded that diltiazem is useful to protect myocardium from ischemia during open heart surgery.