The relationship between myocardial blood flow and contraction by myocardial layer in the canine left ventricle during ischemia

SUMMARY We investigated the relationship between regional myocardial blood flow (MBF) and segmental shortening in 17 open-chest dogs. The left anterior descending coronary artery was cannu-lated and perfused from the left carotid while measuring perfusion pressure. Graded occlusion was produced by a screw clamp. Extent of occlusion was monitored by perfusion pressure. Percent systolic shortening (%AL) was measured using ultrasonic crystals implanted in normal and ischemic endocar-dium and ischemic epicardium. MBF was measured in ischemic and normal endocardium and epicar-dium with tracer microspheres. Dogs underwent 1 to 4 grades of coronary stenosis. Myocardial blood flow both to endocardium and epicardium was found to be linearly related to diastolic perfusion pressure below 50 mmHg (r = 0.803 and 0.748, respectively). Normalized %AL (N%AL) was best related to fraction normal zone MBF in the endocardium by the sigmoidal equation, N%AL = e*