DECREASED AORTIC COMPLIANCE AGGRAVATES SUBENDOCARDIAL ISCHEMIA IN DOGS WITH STENOSED CORONARY-ARTERY

Objectives: The existence of decreased aortic compliance due to arteriosclerosis has been documented in patients with coronary artery disease. The aim of this study was to investigate the effects of decreased aortic compliance on coronary artery disease. Methods: To simulate coronary artery disease, a fixed stenosis was made in the left circumflex coronary artery in dogs. Ten anaesthetised open chest dogs were used. Aortic compliance was decreased by banding the thoracic aorta with adjustable plastic rings. The level of coronary stenosis was adjusted to reduce the baseline flow by no more than 10% but enough to eliminate reactive hyperaemia induced by a 10 s occlusion. Measurements of haemodynamics, regional myocardial segment length, subendocardial ECG, and myocardial tissue PO2 Were performed at five stages (initial control stage, rest and pacing stages without aortic banding, and rest and pacing stages with the aortic banding). Results: Haemodynamic variables were not changed at any stage, except for increased pulse pressure secondary to the aortic banding. During pacing with aortic banding, subendocardial PO2) (Endo) levels were decreased, and subepicardial PO2 (Epi) levels were increased, compared to those without the aortic banding [Endo: 43.2(SD 9.8) v 36.8(10.0) mm Hg, p<0.05; Epi: 34.0(11.5) v 44.4(7.9) mm Hg, p<0.05]. ST elevation on the subendocardial ECG was greater, and myocardial segment shortening was less with the aortic bandage during pacing. Conclusions: When the work of the heart is increased, a decrease in aortic compliance tends to compromise ischaemic myocardium further in the presence of an induced stenosis of a major coronary artery.