Figure Legend
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).