Metabolic and functional response of neonatal pig hearts to the development of ischemic contracture: Is recovery possible?

The potential for functional and metabolic recovery in neonatal hearts afte r the development of ischemic contracture remains controversial and undefin ed. This study documents postischemic recovery of metabolism and function i n the in vivo neonatal heart after the development of onset and peak ischem ic contracture. In piglets on cardiopulmonary bypass, hearts were reperfuse d after the development of either onset (TICo) or peak (TICp) ischemic cont racture. Systolic (developed and systolic function, contractility) and dias tolic (diastolic function, relaxation) performance was assessed throughout reperfusion. Biopsies were obtained at end-ischemia or end-reperfusion to a ssess metabolism. By end-ischemia, the metabolic profiles of both TICo and TICp hearts confirmed energy-stare depletion and purine degradation that wa s quantitatively greater in TICp hearts, Hearts reperfused at TICo had cons istent moderate impairment of developed function, contractility, diastolic function, and relaxation, whereas hearts reperfused at TICp had much more p rofound functional impairment. Diastolic function showed the worst function al recovery. In contrast, systolic function was not significantly altered i n either study group and, thus, did not reflect the actual extent of injury . In addition, TICo hearts either did not further deplete or partially rege nerated energy stores during reperfusion, whereas TICp hearts had further e nergy-store depletion and lactate accumulation. In summary, neonatal hearts reperfused after TICo maintained or partially restored energy stores and h ad significant but incomplete functional recovery. In contrast, further met abolic deterioration and profound functional impairment occurred with reper fusion after TICp, potentially indicating ongoing mitochondrial injury and compromised oxidative phosphorylation.