Serial ultrastructural evaluation of myocardial ischemic injury after infusion of del Nido cardioplegia in the human heart.

Abstract

The safe ischemic time after a single-dose del Nido cardioplegia (DNC) infusion has not yet been established. This study evaluated the progression of myocardial ischemic injury to establish the safe ischemic time after a single-dose DNC infusion in the human heart using a transmission electron microscope. Seven hearts extracted from heart transplant recipients after infusion of 1000mL single-dose DNC were evaluated. Serial left ventricular myocardial tissuesamples were collected every 30minutes for 180minutes. Ischemic injuries in the mitochondria and nuclei were scored from 0 to 3 (0=normal, 0.5=slight, 1=moderate, 2=severe, and 3=irreversible). At the time of extraction, 83.5% of the mitochondria were normal. The proportion of mitochondria with moderate ischemic injury increased gradually from 1.4% at extraction to 52.5% at 180minutes. From 90minutes to 180minutes, the proportion of mitochondria with severe and irreversible injury increased from 0.8% to 4.4% and 0.3% to 1.3%, respectively. A significant linear correlation was identified between the average ischemic injury score of mitochondria and ischemic time (P<.001). Most nuclei showed moderate to severe ischemic injury at every time point (61.0%-85.2%). A significant linear correlation was also found between the average ischemic injury score of nuclei and ischemic time (P<.001). Myocardial ischemic injury progresses gradually, and irreversible ischemic injury begins to occur 90minutes after initial DNC infusion in the adult human heart. Therefore, redosing of DNC may be required after 90minutes of aortic crossclamp time during adult cardiac surgery.