AJP - Heart and Circulatory Physiology, Vol 250, Issue 2 255-H264, Copyright © 1986 by American Physiological Society
Gradients in fiber shortening and metabolism across ischemic left ventricular wall
F. W. Prinzen, T. Arts, G. J. van der Vusse, W. A. Coumans and R. S. Reneman
Blood flow, metabolism, and fiber shortening in various layers of left
ventricular wall were studied during the initial 5 min of ischemia. In
open-chest dogs (n = 51) ischemia was induced by coronary arterial stenosis
(median value of mean perfusion pressure distal to stenosis 3.3 kPa).
Epicardial deformation measurements with an inductive technique allowed
estimation of fiber shortening in inner (eendo,est) and outer layers (eepi)
of left ventricular free wall during the ejection phase. The decrease of
eendo,est occurred within a few seconds after onset of stenosis, whereas
eepi started to decrease 30 s later. After 1 min, eendo,est diminished to
zero concomitantly with a reduction of blood flow and creatine phosphate
content in the inner layers by 68 and 46%, respectively. In contrast a 60%
reduction of eepi was associated with a decrease in blood flow of only 32%
and no significant decrease in creatine phosphate in the outer layers. H+
and inorganic phosphate were released simultaneously into the local venous
blood starting within 1 min of ischemia. During the initial 5 min of
ischemia the content of ATP and glycogen remained unchanged across the
ischemic wall. Present results indicate that the decrease of fiber
shortening in the inner layers is associated with severe metabolic
dearrangements, as reflected by the depletion of creatine phosphate. They
also indicate that, during coronary arterial stenosis, impaired fiber
shortening in the outer layers may result from the impairment of mechanical
function in the inner layers, rather than from metabolic disturbances in
the outer layers themselves.
