Effect of partial oxygen supply on mitochondrial electron transport systemduring complete cardiac ischemia

During complete ischemia we assessed myocardial utilization of the small am ount of oxygen available. We also determined whether blood cardioplegia has any advantage over crystalloid cardioplegia in this setting. Patients with preserved left ventricular myocardial function and without an terolateral wall infarct or aneurysm were included to the study. Intermitte nt cold blood and crystalloid cardioplegia were used in 10 patients (group BC) and 9 patients (group CC), respectively. From myocardial biopsies, obta ined before and after ischemia, complete electron transport system (ETS) en zyme activities (NDH, SDH, NCCR, SCCR, and COX) and lactate content were an alyzed. Biochemical and hemodynamic analyses also were done. Myocardial and blood temperatures were monitored. Ischemic time was longer in group CC (p < 0.05). There were no important di fferences in biochemical and hemodynamic variables between the two groups. In addition, there was no difference in NDH and SDH activities as well as C OX/SCCR and COX/RS-NCCR ratios between the two groups before and after isch emia. After Ischemia, RS-NCCR in group CC and SCCR and COX activities in bo th groups were lower than the control. For all enzymes, activity change rat ios were not different between groups. Myocardial lactate content was incre ased in both groups after ischemia. However, the increase in group BC was l ess (p < 0.01). Based on our findings, we believe that the superiority of blood cardioplegi a over crystalloid cardioplegia does not depend on oxygen content, but on o ther factors such as buffering and free oxygen radical scavenger effects am ong others. However, with the warm and continuous blood cardioplegia techni que, oxygen content might be more important.