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Imaging intramyocardial vascular flows could strongly help to achieve better diagnostic of cardiovascular diseases but no standard imaging modalities allow describing accurately myocardial blood flow dynamics with good spatial and temporal resolution. We recently introduced a novel Doppler imaging technique based on compounded plane waves transmitted at ultrafast frame rate. The high sensitivity and framerate of the Doppler technique enable imaging the intramyocardial blood flow and its dynamics. A special demodulation-filtering process achieved to compensate for the large tissue velocity of the myocardium and a signed power Doppler process enabled the possibility to discriminate arterial and venous flows. Experiments were performed in vivo in N=5 open chest sheep using a conventional ultrasonic probe placed at the surface of the heart. Results show the capability of the technique to image intramyocardial vascular flows in normal physiological conditions with good spatial and temporal resolution. The flow dynamics over the cardiac cycle was investigated and showed a phase opposition of the velocity waveform between arterial and venous flows. Finally, the main diagonal coronary artery was occluded and the vascular flows were found to completely disappear in the ischemic region.