Evolution of regional ischemia distal to a proximal coronary stenosis: self-propagation of ischemia.
The temporal evolution of myocardial ischemia was studied in open chest dogs at constant preload, afterload and heart rate. In one group of animals, a variable circumflex arterial stenosis was used to maintain constant distal circumflex arterial hypotension (40 to 50 mm Hg). During a 3 hour period of stenosis, flow in the subendocardial fourth of the ischemic ventricular wall decreased from 0.22 to 0.09 ml/g per min (P less than 0.02), whereas subepicardial flow was not significantly changed. Local vascular resistance, therefore, doubled in the most ischemic area of myocardium. In a second group of animals in which proximal coronary stenosis was held constant and pressure varied, an ischemia-mediated increase in local vascular resistance was also demonstrated. In addition, a reciprocal relation was observed between changes in flow in the left anterior descending coronary region and changes in collateral flow to the region of the circumflex artery. A coronary steal mechanism and an ischemia-mediated resistance increase may be two means by which ischemia is self-propagating.
D000818:Animals; D001011:Aorta / Q000503:physiopathology; D001794:Blood Pressure; D003326:Coronary Circulation; D003327:Coronary Disease / Q000503:physiopathology*; D004285:Dogs; D004562:Electrocardiography; D004699:Endocardium / Q000503:physiopathology; D006325:Heart Atria / Q000503:physiopathology; D010496:Pericardium / Q000503:physiopathology; D014655:Vascular Resistance