BackgroundNovel cardiovascular magnetic resonance (CMR) techniques and imaging biomarkers are often validated in small animal models or empirically in patients. Direct translation of small animal CMR protocols to humans is rarely possible, while validation in humans is often difficult, slow and occasionally not possible due to ethical considerations. The aim of this study is to overcome these limitations by introducing an MR-compatible, free beating, blood-perfused, isolated pig heart model for the development of novel CMR methodology.Methods6 hearts were perfused outside of the MR environment to establish preparation stability. Coronary perfusion pressure (CPP), coronary blood flow (CBF), left ventricular pressure (LVP), arterial blood gas and electrolyte composition were monitored over 4 hours. Further hearts were perfused within 3T (n = 3) and 1.5T (n = 3) clinical MR scanners, and characterised using functional (CINE), perfusion and late gadolinium enhancement (LGE) imaging. Perfusion imaging was performed globally and selectively for the right (RCA) and left coronary artery (LCA). In one heart the RCA perfusion territory was determined and compared to infarct size after coronary occlusion.ResultsAll physiological parameters measured remained stable and within normal ranges. The model proved amenable to CMR at both field strengths using typical clinical acquisitions. There was good agreement between the RCA perfusion territory measured by selective first pass perfusion and LGE after coronary occlusion (37% versus 36% of the LV respectively).ConclusionsThis flexible model allows imaging of cardiac function in a controllable, beating, human-sized heart using clinical MR systems. It should aid further development, validation and clinical translation of novel CMR methodologies, and imaging sequences.

Both ethical and economic restrictions limit the availability of porcine hearts for in vitro perfusion experiments. Therefore, we tested the feasibility of multiple use of in vitro perfused working hearts for electrophysiological and metabolic investigations. Pig hearts (n=7) rejected for originally planned haemodynamic measurements because of exclusion criteria were perfused in a four-chamber working heart mode. All hearts were kept in steady-state conditions on a low haemodynamic level over 2 h during 75-channel ECG recordings and NADH fluorescence measurements before and after norepinephrine (NE) was administered. QRS and QT interval durations were in a range comparable to in vitro studies and, like QRS and T amplitudes, were found to be sensitive markers of the changing condition of the isolated heart preparation, as myocardial oedema leads to prolonged QRS and QT intervals and declining ECG voltage amplitudes. A change in NADH fluorescence following NE administration was observed in the first 150 min of perfusion, but not later. Considering a time frame of 120 min, multiple use of isolated perfused porcine hearts with low-level haemodynamics may allow a broad spectrum of investigations and could therefore represent a possibility of overcoming the restricted availability of porcine hearts.

This flexible model allows imaging of cardiac function in a controllable, beating, human-sized heart using clinical MR systems. It should aid further development, validation and clinical translation of novel CMR methodologies, and imaging sequences.

No abstract