Estimating cardiac mechanical efficiency in a porcine ex situ working heart model

We introduce a method for assessing cardiac mechanical efficiency via a porcine ex situ biventricular working heart model, designed to closely replicate physiological conditions and improve the evaluation of donor heart viability for transplantation. The method aims to provide decision support for the safe utilization of hearts that might otherwise be discarded. Quantifying the heart’s pumping work against its chemical energy yield, our model advances traditional assessments by incorporating dynamic flow impedances to simulate real-world cardiac loads. We calculate mechanical efficiency by measuring aortic pressure, cardiac output, coronary flow, and blood-gas parameters in six porcine hearts beating in isolation, outside of the body, against computer-controlled dynamic flow impedances. The observed mean mechanical efficiency was 8.0±0.8 % (standard error of the mean), below the physiological norm of 25 %. This discrepancy underscores the influence of ex situ conditions on heart performance, as well as the limitations of standard estimation methods. Impacts of the ex situ setup as well as estimation improvements are discussed. Future research will explore integrating imaging technologies (MRI) to refine mechanical efficiency assessment.