The effect of coronary occulusion on intramyocardial temperature

THE EFFECT OF CORONARY OCCLUSION ON INTRAMYOCARDIAL TEMPERATURE. Anderson, I?, J.E. Douglas, P.J. Hunter* and B.H. Smaill** Departments bf Theoretical 6 Applied Mechanics* and Physiology**, University of Auckland, Auckland, New Zealand. The coronary circulation normally provides a major pathway for the removal of heat generated by the heart. It has been suggested that localized overheating of the myocardium associated with coronary insufficiency may contribute to the development of necrosis (L. Dintenfass in ‘Progress in Microcirculation Research’. Ed D. Garlick, University of New South Wales, pp 100-140, 1981). The objective of this study was to characterize the magnitude and time course of the changes in intramyocardial temperature due to coronary occlusion). The transmural distribution of temperatures in the anterior free wall of the left ventricle (LV) has been measured in anaesthetized mongrel dops. Total occlusion of the left anterior descending coronary artery produced a rapid elevation of LV transmural temperatures. However the magnitude of the temperature changes was typically less than 0.4’C and the initial levels were not sustained. These results are consistent with the predictions of theoretical analyses of cardiac heat transfer during regional coronary occlusion. The latter demonstrates that the magnitude of local elevation of intramyocardial temperature is determined by tlhe geometry of the nonperfused region. The implications of these results will be discussed. Supported by the National Heart Foundation of New Zealand and the Life Insurance Medical Research Fund of Australia and New Zealand.

THE EFFECTS OF ISCHAEMIA ON THE FINE STRUCTURE OF THE ATRIOVENTRICULAR CONDUCTING TISSUES OF THE DOG HEART. L.C. Armiger and J.G. Wilson. Department of Pathology, School of Medicine, University of Auckland, Auckland, New Zealand. The effects of ischaemia on the fine structure of the atrioventricular (AV) conducting tissues of the heart have been studied in 8 dogs in which ligation of the septal and the distal circumflex branches of the left The dogs were coronary artery resulted in atrioventricular block. Surgical control maintained for 30-180 minutes after arterial ligation. tissue from 11 dogs maintained for similar periods of time under identical conditions of operation but without arterial ligation was also studied. In all cases the AV junctional tissues were cut into a series of slices lmm thick, which were examined by light and electron microscopy using a large specimen resin-embedding technique. The earliest change detected in all conducting cells was widespread dilation of the sarcoplasmic reticulum, followed by clumping of the nuclear chromatin, disappearance of glycogen granules (from Purkinje and transitional cells) and mitochondrial degeneration comprising swelling, loss of matrix density, disorganisation and disappearance of cristae, and the presence After 180 minutes these changes had of amorphous dense inclusions. become severe and were similar to those seen in adjacent ventricular myocardium. Our observations do not support the view that the specialised cardiac conducting tissue is more resistant to ischaemic injury than "working" cardiac muscle. (Supported

by a grant

from

the

Medical

Research

Council

of New Zealand).