Purpose: Fatal necrosis of the myocardium can be avoided by prompt reperfusion at the onset of myocardial ischemia. Therefore, rapid identification of the range and degree of the ischemic regions is essential for diagnosis and subsequent correct treatment in the early stage of ischemic heart disease. In this paper, the decrease in the propagation velocity of the myocardial contraction response after ischemia is detected quantitatively in several seconds by ultrasonic measurements in multiple swine hearts. Methods: Ultrasonic measurement was applied to the interventricular septum (IVS) of five open-chest swine under normal conditions. Ischemia in the IVS was then induced by avascularizing the left anterior descending (LAD) coronary artery, and ultrasonic measurement was applied to the ischemic IVS within several seconds. By applying the phased-tracking method to the acquisition RF signals under each condition, velocity waveforms with minute vibration were simultaneously obtained at about 3,000 points in the IVS. Moreover, using cross-correlation between the resultant vibration velocity waveform at each measurement point and that at the reference point, the propagation of the myocardial contraction response was visualized as spatial transition of the delay time. Results: In the IVS of five open-chest swine, the myocardial contraction response propagated from the basal side to the apical side. The propagation velocity was almost constant at 2.7±0.5 m/s under normal conditions. On the other hand, an approximately 31% decrease in the propagation velocity to 1.9±0.5 m/s was observed about 5 seconds after LAD avascularization. Furthermore, about 7 seconds after LAD avascularization, an approximately 50% decrease in the propagation velocity to 1.4±0.3 m/s was observed. Conclusion: In five swine, the propagation velocity of the myocardial contraction decreased by about 50% in about 7 seconds from a normal to ischemic state. This suggests that myocardial ischemic regions can be identified noninvasively by ultrasonic measurement.