Computer-aided thermographic evaluation of disturbances of the coronary adaptive reserve: an experimental study

Brief episodes of severe ischaemic loads have been reported to attenuate or abolish the vascular autoregulatory capacity, including reactive hyperaemic vasodilation, in the coronary bed. It is suggested that the developed loss of the coronary adaptive reserve and the consecutive ultrastructural alterations can be considered an experimental model for the human effort anginal attacks occurring without significant mechanical constriction of the vessels. The functional morphologic patterns in this state were analysed by the new quantitative technique which is based on the computerized evaluation of cardiac thermograms taken with a thermovision (AGA 750) equipment. In the isolated perfused heart of rabbits, the total adaptive loss developed in the overall flow (cessation of reactive hyperaemia) was found to be associated with slow reacting coronary vessels in the cardiac surface, a delayed shift of the computerized thermographic profiles to warmer ranges during reactive hyperaemia. The pattern strongly suggested a redistribution of flow from the subendocardium. In further observations, simulated emergency coronary bypass operations on dog hearts revealed another distinct thermographic pattern: a reduced vascular adaptive range without considerable delay in reactivity. The studies demonstrated the usefulness of quantitative thermography in visualising and differentiating the various types of coronary dysfunction.