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Figure 1(a) Intramural electrode array is depicted on the polar projection of canine heart. Shaded area denotes the boundary of ischemic region. 1(b) Sub epicardial electrograms from the ischemic zone from three separate experiments between 3 and 5 minutes after coronary artery occlusion. PVC (indicated by arrows) was in each case preceded by an augmentive cycle of ST-T wave alternans, which was repetitive.
Figure 2 Transmural unipolar electrograms from needle in the center of ischemic region recorded at 2 mm intervals from the epicardium, showing a continuous tracing displayed during the ST-T wave alternans 4’30” after coronary occlusion. The arrows indicate the development of transmural graded responses with alternate sinus beats, culminating in the PVC.
Figure 3 Activation map of PVC. The earliest activation occurred at the ischemic sub-endocardium. Spread of activation in the sub-endocardium is relatively rapid progressing in a radial fashion across the sub-endocardium overlying the ischemic region. Sub-epicardial activation emerged later at the ischemic border in two separate locations diametrically opposite across the ischemic region. Spread into the ischemic sub-epicardium progressed slowly, persisting up to 180 ms after the earliest onset of PVC, however failing to activate all of the ischemic region (white area).