Can stunned hearts be resuscitated? Evaluation of aspartate/glutamate secondary blood cardioplegia using magnetic resonance spectroscopy

Objectives: Reperfusion of ischemic hearts with warm, substrate-enriched, blood cardioplegia may alleviate post-ischemic metabolic and functional derangements. This study investigates this possibility using (31)P magnetic resonance (MR) spectroscopy. Methods: Fifteen blood-perfused Langendorff pig hearts were subjected to 30 min of total, normothermic ischemia. Control hearts (n=8) were reperfused with blood for 40 min. Experimental hearts (n=7) received 20 min of aspartate/glutamate (asp/glu) enriched blood cardioplegic solution, followed by 20 min of normal blood. (31)P MR spectroscopy was used to observe cellular energetics and intracellular pH (pHi) throughout the experiments. Left-ventricular function and myocardial oxygen consumption were evaluated before and after ischemia. Results: MR spectra showed no improvement in the rate or extent of high-energy phosphate recovery with asp/glu cardioplegia, but showed a transient increase in pHi during cardioplegic reperfusion (p