Effects of regional myocardial ischaemia on coronary artery calibre in the rabbit.
Microangiographic and electron microscopic studies were undertaken in isolated, perfused rabbit hearts to examine the effects of acute regional myocardial ischaemia on coronary artery calibre, vascular resistance and ultrastructure. Selective left coronary angiograms were recorded prior to, after 90 min of acute regional myocardial ischaemia induced by occlusion of the marginal left ventricular branch of the circumflex artery, and after reperfusion for 5 min. Vasodilation occurred in the proximal left anterior descending artery (9 +/- 1%, P less than 0.01) and the unoccluded part of the marginal branch (21 +/- 1%, P less than 0.001) during ischaemia which reversed on reperfusion. During reperfusion, coronary vascular resistance increased by 43 +/- 10% (P less than 0.001) despite mild vasodilation of vessels in the ischaemic zone (up to 10 +/- 1%, P less than 0.01). Failure of reperfusion occurred in vessels smaller than 30 microns in diameter (terminal arterioles) and was associated with ultrastructural damage in the ischaemic zone which was particularly prominent at the apex. These findings suggest that failure of reperfusion following 90 min of acute regional myocardial ischaemia in the rabbit is associated with damage to terminal arterioles and capillaries and that the calibre of the larger coronary vessels is maintained. Failure of reperfusion after prolonged myocardial ischaemia may occur despite arterial dilatation in the ischaemic zone.
Department of Cardiology, University of Wales College of Medicine, Heath Park, Cardiff, UK.
N A
NA
Flores
S K
SK
Singhrao
R L
RL
Davies
D J
DJ
Sheridan
D000818:Animals; D001158:Arteries / Q000473:pathology; D001160:Arterioles / Q000502:physiology; D002196:Capillaries / Q000502:physiology; D017023:Coronary Angiography; D003327:Coronary Disease / Q000473:pathology*; D003331:Coronary Vessels / Q000473:pathology*; D008297:Male; D008854:Microscopy, Electron; D015425:Myocardial Reperfusion; D011817:Rabbits; D014655:Vascular Resistance / Q000502:physiology; D014661:Vasoconstriction; D014664:Vasodilation