Magnetic resonance imaging of cardiac function and myoca

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The compliance of the cardiac muscle in diastole is important to normal filling of the heart prior to ejection. In the last year we performed the first non-invasive measurements of the elasticity and viscousity of the myocardium. We did this using a MRI phase-shift technique developed by our group called DENSE. We obtained very different results in the beating heart from previously published numbers obtained in isolated tissue samples. The living muscle is markedly more compliant and less viscous. Based on these data we plan to look into the physiological conditions that affect myocardial stiffness, and extend this measurement to human volunteers and potentially patients with diastolic dysfunction. We also performed image based measurements of the blood volume of the myocardium and mean flow velocity in the capillaries. We observed the organized orientation of the capillaries in the mocardial wall. Our data also supported the notion that unlike other organs, microcirculation in the heart oscillates like a the sponge being periodically squeezed by the muscle contraction itself. This has implications on how uniform fresh blood is delivered to the heart muscle. We are now conducting measurements to gauge the degree of heterogeneity in regional perfusion and work output of the myocardium. We are also performing direct imaging of the squeezing effect of the myocardium to better understand this particular dynamics of blood flow.