Cardioprotection with esmolol-based cardioplegia for non-infarcted and infarcted rat hearts

OBJECTIVES: Esmolol-based cardioplegic arrest offers better cardioprotection than crystalloid cardioplegia but has been compared experimentally with blood cardioplegia only once. We investigated the influence of esmolol crystalloid cardioplegia (ECCP), esmolol blood cardioplegia (EBCP) and Calafiore blood cardioplegia (Cala) on cardiac function, metabolism and infarct size in non-infarcted and infarcted isolated rat hearts. METHODS: Two studies were performed: (i) the hearts were subjected to a 90-min cardioplegic arrest with ECCP, EBCP or Cala and (ii) a regional myocardial infarction was created 30 min before a 90-min cardioplegic arrest. Left ventricular peak developed pressure (LVpdP), velocity of contractility (dLVP/dt(max)), velocity of relaxation over time (dLVP/dt(min)), heart rate and coronary flow were recorded. In addition, the metabolic parameters were analysed. The infarct size was determined by planimetry, and the myocardial damage was determined by electron microscopy. RESULTS: In non-infarcted hearts, cardiac function was better preserved with ECCP than with EBCP or Cala relative to baseline values (LVpdP: 10028% vs 86 +/- 11% vs 57 +/- 7%; P=0.002). Infarcted hearts showed similar haemodynamic recovery for ECCP, EBCP and Cala (LVpdP: 85 +/- 46% vs 89 +/- 55% vs 56 +/- 26%; P=0.30). The lactate production with EBCP was lower than with ECCP (0.6 +/- 0.7 vs 1.4 +/- 0.5 mu mol/min; P=0.017). The myocardial infarct size and (ECCP vs EBCP vs Cala: 16 +/- 7% vs 15 +/- 9% vs 24 +/- 13%; P=0.21) the ultrastructural preservation was similar in all groups. CONCLUSIONS: In non-infarcted rat hearts, esmolol-based cardioplegia, particularly ECCP, offers better myocardial protection than Calafiore. After an acute myocardial infarction, cardioprotection with esmolol-based cardioplegia is similar to that with Calafiore.