Ventricle-specific metabolic differences in the newborn piglet myocardium in vivo and during arrested global ischemia.

Ventricular dysfunction is reported greater in the left (LV) versus right ventricle (RV) in infants following surgically induced ischemia. Ventricle-specific differences in baseline metabolism may alter response to ischemia thus affecting postischemic functional recovery. This study identifies ventricle-specific metabolic differences in the newborn (piglet) heart at baseline (working) and during ischemia (arrested). Baseline LV citrate synthase (CS) and hydroxyacyl-CoA dehydrogenase (HAD) activities were 15% and 18% lower (p < 0.02), whereas creatine kinase (CK) and phosphofructokinase (PFK) activities were 40% and 23% higher (p < 0.04) than the RV. Baseline LV glycogen reserves were also 55% higher (p = 0.004). By 15 min of ischemia, LV ATP was 20% lower (p < 0.05), lactate was 51% higher (p = 0.001), and hydrogen ions (H) were 43% higher (p = 0.03) compared with the RV. These differences persisted for the entire ischemic period (p < 0.02). After 45 min of ischemia, the LV used 58% less (p < 0.05) glycogen than the RV. These findings demonstrate that the enhanced glycolytic capacity of the newborn LV was accompanied by greater anaerobic end-product accumulation and lower energy levels during ischemia. This profile may offer one explanation for greater LV-dysfunction relative to the RV in children following ischemia.