Effect of nifedipine in hypothermic cardioplegia: a phosphorus-31 nuclear magnetic resonance study

The ability of nifedipine to enhance myocardial protection was assessed on isolated perfused rat hearts subjected to 180 min of hypothermic (20 degrees C), global ischemia, followed by 45 min of normothermic reperfusion. Intracellular pH, ATP, Pi and phosphocreatine content were serially measured at 4 min intervals by phosphorus-31 nuclear magnetic resonance spectroscopy and correlated with simultaneously recorded hemodynamic parameters. Addition of nifedipine (0.075 mumol/l and 0.5 mumol/l) to Saint Thomas' cardioplegic solution reduced Pi accumulation during ischemic arrest and increased phosphocreatine levels during reperfusion. Post-ischemic functional recovery was not improved at a drug concentration of 0.075 mumol/l and was depressed at 0.5 mumol/l. These results clearly show that the presence of nifedipine in Saint Thomas' cardioplegic solution does not provide significant additional myocardial protection under hypothermic conditions.