NICARDIPINE - MYOCARDIAL PROTECTION IN ISOLATED WORKING HEARTS

The effectiveness of the calcium antagonist nicardipine in protecting the ischemic myocardium was evaluated using the hemodynamic recovery of isolated working rat hearts subjected to hyperkalemic cardiac arrest followed by ischemia at 37.5-degrees-C and 10-degrees-C. Rat hearts (n = 51) received 20 mL of cardioplegia and were subjected to 27 minutes of ischemia at 37.5-degrees-C. Group A (control) did not receive nicardipine. Groups B through F received nicardipine in the cardioplegia with total doses ranging from 2 mug to 6 mug. Group A had 46% survival of ischemia, whereas groups C (3 mug) and D (4 mug) had survival rates of 88% and 100%, respectively (p < 0.05). The recovery of aortic flow after ischemia was 35% in group A, compared with 76% in group B (2 mug) and 81% in group D (p < 0.05). Group A had 49% postischemic recovery of cardiac output, whereas groups B and D had 82% and 85% recovery (p < 0.05). The postischemic recovery of stroke volume was 48% in group A compared with 84% in group B, 87% in group D, and 73% in group E (5 mug) (p < 0.05). Additional rats were exposed to 210 minutes of ischemia (n = 41) or 240 minutes of ischemia (n = 56) at 10-degrees-C. Control groups did not receive nicardipine, whereas treatment groups received nicardipine in the cardioplegia with total doses ranging from 1.4 mug to 6.4 mug. There were no significant differences in the survival of ischemia or the recovery of function after ischemia at 10-degrees-C. We conclude that nicardipine offers significant protection to the ischemic rat myocardium at normothermia, with an optimal dose of 2 to 4 mug. We have been unable to demonstrate any beneficial effect from the administration of nicardipine at 10-degrees-C.