Abstract 2525: Non-ischemic Myocardial Acidosis Adversely Affects Microvascular and Myocardial Function and Triggers Apoptosis During Cardioplegia
Background: We investigated if the degree of non-ischemic myocardial acidosis during a period of cardioplegic arrest differentially affects the recovery of microvasular/left ventricular (LV) function, and occurance of apoptosis.
Methods and Results: Isolated hearts from donor rabbits were perfused with oxygenated-diluted-blood on a modified Langendorff apparatus. The hearts were arrested for 60 minutes with cold (15 ±1°C) diluted-blood cardioplegia (C-BCP) administered continuously under non-ischemic conditions. The myocardial pH was adjusted and measured continuously with a glass electrode system. Myocardial pH was maintained at 7.2, 6.5, or 6.2 (n = 6/group) during 60 minutes of arrest. Hearts were then reperfused for 120 minutes with oxygenated-diluted-blood. Recovery of left ventricular and microvascular endothelial function was better with a myocardial pH of 7.2 than with a pH of 6.5 or 6.2 (p<0.05). Myocardial pH of 7.2 also induced less caspase-3 activation and apoptotic cells (TUNEL staining) than a pH of 6.5 or 6.2 (p<0.05). Regression analysis demonstrated that a significant relationship existed between the recovery of endothelial microvascular (r = 0.64, p=0.03) or LV (r = 0.62, p=0.04)) function and myocardial pH: the lower the pH, the worse the microvascular and LV function recovery.
Conclusion: Severe acidosis during cardioplegic arrest, independant of ischemia, adversely affects recovery of microvascular and LV function and increases indices of apoptosis . This effect on apoptosis may influence long term outcome after cardiac surgery.