Interactions: mechanics, metabolism and perfusion

Abstract

Weiss: I would like to comment about mechanics, oxygen consumption and cardiac metabolism during infarction or ischemia. It’s clear that the myocardial response to a reduction in blood flow is a loss of mechanical function and a decrease in oxygen consumption. I have studied this problem for many years, as have many other people. It is clear that during coronary artery blockage there is a large rapid drop in oxygen consumption and many changes within the cell such as loss of high energy phosphates. Because the matabolic rate drops to 20% of the control, the mechanical function also stops. Dr Gallagher and Dr Li have shown the loss of mechanical function within the area of ischemia and pointed out again the very sharp mechanical disfunction which seems to be coupled with very sharp differences in metabolism. One of the aspects of this is in alterations of lipid metabolism and mechanical properties. It would be very useful to couple those. We have been measuring oxygen consumption in the ischemic zone for many years and it would be interesting to see what happens to myocardial efficienty. Maybe not in the center, but in less ischemic tissue there are probably going to be large changes in the mechanical efficiency or in oxygen cost of doing work. This has not been extensively studied. Finally there have been several studies, of Perl and others, trying to model the mechanical aspects of ischemia. These can, if they pose experimental questions, be extremely useful for the experimentalists. It is my hope that this interaction of metabolic rate, local metabolic factors within the heart, the mechanical events, efficiency and modeling will eventually lead to some synthesis which gives a better understanding of what is occurring within the ischemic zone.