MYOCARDIAL PROTECTION IN THE ACUTELY INJURED HEART - HYPERPOLARIZING VERSUS DEPOLARIZING HYPOTHERMIC CARDIOPLEGIA

Objectives: The superiority of hyperpolarized arrest with adenosine tr iphosphate-sensitive potassium channel openers over standard hyperkale mic depolarizing cardioplegia during normothermic ischemia has been do cumented, This study examined the hypothesis that pinacidil would prov ide superior protection in a more clinically relevant model of an acut ely injured heart and hypothermic cardioplegic arrest, Methods: In a b lood-perfused, parabiotic, rabbit heart Langendorff model, hearts unde rwent 15 minutes of unprotected global normothermic ischemia before th e administration of 50 mi of cardioplegic solution at 4 degrees C, fol lowed by 50 minutes of hypothermic (15 degrees C) ischemia and 30 minu tes of reperfusion, The cardioplegic solutions administered consisted of Krebs-Henseleit solution alone (N = 6), Krebs-Henseleit solution wi th pinacidil (50 mu mol/L; N = 10), Krebs-Henseleit solution with pina cidil (50 mu mol/L) and glibenclamide (a potassium channel blocker, 10 mu mol/L; N = 8), or St, Thomas' Hospital solution (N = 8), The perce nt recovery of developed pressure, linear diastolic pressure-volume re lationships, and coronary blood dow were con;pared, Results: The perce nt recovery of developed pressure was 32.8% +/- 2.8%, 43.0% +/- 4.3%, 46.5% +/- 2.2%, and 49.3% +/- 2.7% for the Krebs-Henseleit, the Krebs- Henseleit with pinacidil and glibenclamide, the St, Thomas' Hospital, and the Krebs-Henseleit with pinacidil groups, respectively, No hearts had ventricular fibrillation on reperfusion, Conclusions: During hypo thermic hyperpolarized arrest, as opposed to normothermic ischemia as in our previous studies, there was neither an increased incidence of v entricular fibrillation nor prolonged electrical activity when compare d dth results during traditional hyperkalemic arrest, Myocardial prote ction by St. Thomas' Hospital solution and pinacidil was superior (p = 0.009) to that with Krebs-Henseleit solution alone, The protection pr ovided by pinacidil was lost with the addition of glibenclamide, indic ating that the drug has adenosine triphosphate-sensitive potassium cha nnel activity during hypothermia.