Résumé
This study evaluated the application of quantitative tissue velocity imaging (QTVI) in assessing regional myocardial systolic and diastolic functions in dogs with acute subendocardial ischemia. Animal models of subendocardial ischemia were established by injecting microspheres (about 300 microm in diameter) into the proximal end of left circumflex coronary artery in 11 hybrid dogs through cannulation. Before and after embolization, two-dimensional echocardiography, QTVI and real-time myocardial contrast echocardiography (RT-MCE) via intravenous infusion of self-made microbubbles, were performed, respectively. The systolic segmental wall thickening and subendocardial myocardial longitudinal velocities of risk segments before and after embolization were compared by using paired t analysis. The regional myocardial video intensity versus contrast time could be fitted to an exponential function: y=A.(1-exp(-beta.t)), in which the product of A and beta provides a measure of myocardial blood flow. RT-MCE showed that subendocardial normalized A.beta was decreased markedly from 0.99+/-0.19 to 0.35+/-0.11 (P0.05), the longitudinal peak systolic velocities (Vs) and early-diastolic peak velocities (Ve) recorded by QTVI were declined significantly (P<0.05). Moreover, the subendocardial velocity curves during isovolumic relaxation predominantly showed positive waves, whereas they mainly showed negative waves before the embolization. This study demonstrates that QTVI can more sensitively and accurately detect abnormal regional myocardial function and post-systolic systole caused by acute subendocardial ischemia.