FUNCTIONAL SIGNIFICANCE OF REGIONAL ISCHEMIC CONTRACTION ABNORMALITIES

To evaluate the progression of segment function following induction of ischemia, the left anterior descending coronary artery was ligated (8 dogs) or cannulated and perfused at various pressures via a bypass-oxygenator (6 dogs). Mercury-in-silastic length gauges were sutured to the anterior left ventricle, and pressure was recorded by a catheter-tipped transducer. Segment function was determined from the area of the pressure-length loop by plotting instantaneous left ventricular pressure against segment length and by evaluation of the degree of systolic shortening. Segment function decreased linearly as flow in the left anterior descending artery was decreased in a stepwise fashion by reduction in perfusion pressure from 100-20 mm Hg. With both left anterior descending coronary artery ligation and stepwise flow reduction, the pressure-length loop invariably showed 4 clearly identifiable morphologic patterns which relate conceptually to the specific left ventricular contraction patterns: dyssynchrony, hypokinesis, akinesis and paradoxic systolic expansion. Re-oxygenation following occlusion invariably revealed return to a normal pattern in reverse order. A consistent and predictable progression of segmental contraction abnormalities occurs with ischemia.