A canine model of transient myocardial dysfunction regional shortening in the presence of critical stenosis and cardiac stimulation.

An experimental model of exercise-induced angina pectoris was developed in anesthetized dogs. Two i.v. bolus injections of isoproterenol (ISO, 0.25 microgram/kg; time interval: 10 min) were administered, followed by constriction of the circumflex coronary artery (LCX; critical stenosis). Further i.v. bolus injections of ISO were administered before and after i.v. infusion of 0.9% NaCl (control infusion). Stenosis of the LCX did not modify regional function at rest as assessed with ultrasonic crystals implanted subendocardially both in the distribution areas of the circumflex coronary artery and of the left anterior descending coronary artery (LAD). In the presence of critical stenosis, ISO induced a reproducible, transient decrease in systolic shortening and percent systolic shortening in the area supplied by the LCX and a marked increase in systolic shortening and percent systolic shortening in the area supplied by the LAD. During a 60-min observation period following control infusion, no further substantial changes in regional dimensions were observed. The ISO-induced hemodynamic changes were reproducible during this period. The experimental model of exercise-induced angina pectoris presented in this study can be assumed to provide a reliable basis for evaluating the efficacy of various therapeutical interventions.