Ex Vivo Heart Preservation: Impact of an Acellular Hemoglobin-Based Oxygen Carrier on Myocardial Function and Energy Metabolism

Abstract

Purpose The optimal method of oxygen delivery during ex vivo heart preservation has not been established. Donor blood contains multiple elements that may propagate myocardial injury. We sought to determine the impact of an acellular hemoglobin-based oxygen carrier (Hemopure ™, OPK Biotech, USA) on myocardial function and energy metabolism. Methods and Materials Twelve pig hearts were procured following cardioplegic arrest and perfused ex vivo at 37 o C. Group 1 hearts (G1, N=6) were perfused with a donor blood-STEEN solution ([Hb]=40g/L) and Group 2 hearts (G2, N=6) were perfused with a Hemopure-STEEN solution ([Hb]=40g/L). Hearts were transitioned into working mode for assessments at 1 (T1), 3 (T3), and 5 (T5) hours of ex vivo perfusion. Myocardial function and energy metabolism were assessed by pressure-volume loop analysis and 31 P magnetic resonance spectroscopy, respectively. Results G2 hearts demonstrated superior energy metabolism at T1 (inorganic phosphate/phosphocreatine: G2=0.29±0.04 vs. G1=0.49±0.03, p Table 1 ). The development of myocardial edema in G2 hearts over the preservation interval (weight gain: G2=17±2 vs. G1=7±1 grams/hr, p Conclusions Ex vivo perfusion with Hemopure may provide superior preservation of myocardial energy metabolism; however, methods to minimize myocardial edema are required to facilitate its use as a donor blood alternative. Table 1 Left ventricular diastolic function EDPVR Tau (ms) dP/dt min (mmHg/s) T1 Group 1 0.29±0.03 56±5 −960±102 Group 2 0.35± 0.04 62±6 −647±60 p value 0.27 0.50 0.03 T3 Group 1 0.36±0.05 68±2 −741±55 Group 2 0.71±0.11 113±13 −391±32 p value 0.01 T5 Group 1 0.50±0.07 77±6 −574±48 Group 2 1.38±0.31 138±24 −279±24 p value 0.04 0.05 dP/dt min , minimum rate of pressure change; EDPVR, end-diastolic pressure volume relationship