Assessment of transmyocardial perfusion in alligator hearts

BACKGROUND: Techniques for achieving myocardial perfusion directly from the left ventricular chamber are currently under investigation. Although originally based on the anatomy of reptilian hearts, which are rich in transmural channels and reported to have a poorly developed coronary vasculature, the blood flow capacity of a transmyocardial blood supply has not been studied in these hearts. With the ultimate goal of providing insight into the potential for achieving transmyocardial perfusion in human hearts, we studied the relative contribution of transmyocardial and coronary perfusion in alligator hearts. METHODS AND RESULTS: After explanation from six American alligators, the left ventricle was instrumented, and coronary arteries were perfused with oxygenated physiological solution. Using microspheres to estimate regional myocardial perfusion in the beating hearts, we show that although the epicardium was well perfused by the coronary arteries (0.20 +/- 0.08 versus 0.07 +/- 0.01 mL.min-1.g-1 owing to flow from the ventricular chamber), a significant proportion of endocardial perfusion was from the ventricular chamber (0.21 +/- 0.07 mL.min-1.g-1 from the left ventricle versus 0.13 +/- 0.04 mL.min-1.g-1 from coronary arteries). CONCLUSIONS: A significant amount of direct transmyocardial perfusion is present in alligator hearts. The conditions that apparently permit this situation in reptilian hearts are reviewed, and their implications for aiding in the optimization of techniques for achieving transmyocardial flow in humans are discussed.