AJP - Heart and Circulatory Physiology, Vol 242, Issue 5 867-H874, Copyright © 1982 by American Physiological Society
Transmural variation in the relationship between myocardial infarct size and risk area
S. Koyanagi, C. L. Eastham, D. G. Harrison and M. L. Marcus
To test the hypothesis that the relationship between infarct area (IA) and
area at risk (AR) varies in different layers of the left ventricle (LV), we
occluded the circumflex coronary artery for 48 h in 20 conscious dogs. AR
was determined by postmortem coronary stereoarteriography, and infarct area
by pathological examination. Both AR and IA were divided into four layers:
posterior papillary muscle (PPM), subendocardium (Endo), midwall, and
subepicardium (Epi) and quantified with planimetry. Hemodynamics and
regional myocardial flow with tracer microspheres (7-10 micrometers diam)
were measured before and after coronary occlusion. IA was closely
correlated with AR for PPM (r = 0.96), Endo (r = 0.97), and Epi (r = 0.92).
However, the slope of IA/AR for Endo (1.30 +/- 0.08) was significantly
steeper (P less than 0.05) than that for Epi (0.89 +/- 0.11); furthermore,
the intercepts at zero infarction for PPM (0.5 +/- 0.1% of LV), Endo (4.2
+/- 0.4%), and Epi (0.1 +/- 0.7%) were significantly different from each
other. Regional blood flow measurements indicate that the differences in
IA/AR in various layers reflected earlier and greater total collateral flow
to the noninfarcted AR in the epicardium. Thus IA/AR for the entire LV is a
composite representing separate IA/AR specific to various transmural layers
of the LV. In addition, this study demonstrates that the lateral border
zone between the IA and the AR is minimal (less than 3-5 mm) in the
subendocardium and midwall layers of the left ventricle.
