Development of a human heart-sized perfusion system for metabolic imaging studies using hyperpolarized [1- C]pyruvate MRI.

Purpose: Increasing worldwide demand for cardiac transplantation has spurred new developments to increase the donor pool. Normothermic preservation of heart grafts for transplantation is an emerging strategy to improve the utilization of marginal grafts. Hyperpolarized MR using metabolic tracers such as [1- C]pyruvate, provide a novel means of investigating metabolic status without the use of ionizing radiation. We demonstrate the use of this methodology to examine ex vivo perfused porcine heart grafts.

Methods: Hearts from three 40-kg Danish domestic pigs were harvested and subsequently perfused in Langendorff mode under normothermic conditions, using an MR-compatible perfusion system adapted to the heart. Proton MRI and hyperpolarized [1- C]pyruvate were used to investigate and quantify the functional and metabolic status of the grafts.

Results: Hearts were perfused with whole blood for 120 min, using a dynamic contrast-enhanced perfusion experiment to verify successful myocardial perfusion. Hyperpolarized [1- C]pyruvate MRI was used to assess the metabolic state of the myocardium. Functional assessment was performed using CINE imaging and ventricular pressure data. High lactate and modest alanine levels were observed in the hyperpolarized experiment. The functional assessment produced reduced functional parameters. This suggests an altered functional and metabolic profile compared with corresponding in vivo values.

Conclusion: We investigated the metabolic and functional status of machine-perfused porcine hearts. Utilizing hyperpolarized methodology to acquire detailed myocardial metabolic information-in combination with already established MR methods for cardiac investigation-provides a powerful tool to aid the progress of donor heart preservation.