Protective effect of diltiazem against ischemia-induced decreases in regional myocardial flow in rat heart

Diltiazem has cardioprotective properties following myocardial ischemic inj ury. However, there are controversial results regarding the beneficial effe cts of diltiazem on regional myocardial flow after ischemia. Therefore, we investigated the effect of diltiazem on changes in regional myocardial flow due to ischemia for different periods. Non-radioactive colored microsphere s were used for this measurement in isolated rat heart. After 20 or 40 min of global ischemia and 40 min of reperfusion, regional myocardial flow was decreased, especially in the endocardial layer. The endocardial/epicardial ratio was also decreased. The decreases in endocardial flow and the endocar dial/epicardial ratio were more remarkable after 40 min of ischemia than af ter 20 min of ischemia. Diltiazem (10(-6) M), which was administered 15 min before ischemia. prevented only the decrease in endocardial flow and endoc ardial/epicardial ratio after 20 min of ischemia, whereas it did not preven t that after 40 min of ischemia. Nifedipine (2 x 10(-6) M) did not exert a cardioprotective effect. These findings suggested that the effect of ischem ia is marl;ed in the endocardium and, also, that the protective effect of d iltiazem is seen only during a decrease in endocardial flow following short -term and reversible ischemia. (C) 2000 Elsevier Science B.V. All rights re served.