Abstract 2726: Noninvasive Quantification of Myocardial Blood Flow in Mice: Validation of Myocardial Contrast Echocardiography using Microspheres
Background and Aim: Myocardial contrast echocardiography (MCE) has been validated in the quantification of myocardial blood flow in human and large animals. Although mice are used to elucidate genetic mechanisms in cardiovascular disease, assessment of coronary perfusion has been limited by lack of validated noninvasive techniques. Our goal was to compare MCE with the invasive measurements of myocardial blood flow using microspheres both at rest and with vasodilators.
Methods: MCE was performed in C57BL6 wild-type mice, at rest (n=5) or after hyperemia induced by intravenous infusion of adenosine (140μg/kg/min, n=5). DefinityTM was infused at a rate of 1–3μl/min. Parasternal long axis views were acquired (14MHz probe, mechanical index 0.24, frame rate 25–30 Hz). Time versus intensity (I in dB) replenishment curves were obtained following a burst of 10 high energy frames and the beta coefficient (microbubble velocity in s−1) and I plateau (A) were calculated. Immediately following MCE, 180000 fluorescent 10μm microspheres were injected into the left ventricle with simultaneous withdrawing of a reference blood sample at a rate of 200μl/min. After euthanasia, the left ventricle was digested and processed for quantification of myocardial blood flow by microspheres.
Results: There were no differences in blood pressure and heart rate between control and adenosine-treated mice (Table⇓). Higher microsphere-derived myocardial flow rate, beta and the product of A*beta were documented in mice infused with vasodilators compared to mice at rest (Table⇓). Beta and A*beta correlated closely with myocardial flow rates as quantified by microspheres (both r=0.89, P=0.001).
Conclusions: MCE is able to detect myocardial perfusion in mice at rest and its increase after adenosine-induced coronary vasodilation. MCE parameters correlate closely with myocardial flow rate by microspheres, potentially allowing noninvasive and rapid quantification of myocardial blood flow.