Abstract
Introduction Magnetic Resonance (MR) allows non invasive characterization of cardiac structure, function and metabolism. Fundamental studies are usually performed on isolated rodent heart. In order to provide a model closer to human heart, we present a MR-compatible isolated working heart system for large animals. Methods Hearts from pigs were perfused ex vivo in a working mode with a mixture of blood and Tyrode. MR acquisition sequences were performed at 1.5T with ECG triggering and using standard clinical hardware. Cine short axis images were acquired to calculate ejection fraction (EF), and myocardial tissue alterations were assessed from parametric T1-maps (Look-locker method). Intraventricular pressures were recorded continuously and cardiac pacing was tested for inducing arrhythmia. Results During perfusion, heart rate increased from 90 to 120 bpm associated with a reduction of the diastolic filling period and a progressive alteration of the mechanical function: decrease in dP/dtmax (–20%) and aortic flow (–25%) with an EF at 20%. T1-maps showed a spatially homogeneous distribution over the myocardium in a normal heart, while variations on anterior and posterior faces were reported on a pathological heart corresponding to observable ischemic area. Tagging, coronary artery imaging sequences were also performed to supplement assessment of cardiac function and structure. Ventricular tachycardia was induced by pacing at 120 to 180 bpm during MR acquisitions without image degradation. Conclusions We successfully performed blood-perfusion of isolated pig hearts with working left atrium and ventricle inside a MR environment, allowing simultaneous assessment of cardiac structure, mechanics and electrophysiology. This setup allows study of intrinsic mechanical, electrophysiological and metabolic functions and their modifications under (patho)-physiological conditions on animal heart close to the human heart, with cardiac loads and metabolic supply control.
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