Effects of major coronary artery stenosis on the pressure-flow relationship of an adjacent intact coronary artery branch in isolated supported canine left ventricle.

We investigated whether the relationship between the mean left anterior descending and septal coronary blood flow and the mean perfusion pressure varies with left circumflex coronary stenosis. We used excised, perfused canine heart preparations (n = 10), in which variables to influence the myocardial oxygen demand and supply relation can be fairly well controlled. The results showed that coronary blood flow in the adjacent, non-stenosed coronary artery increased significantly following LCX stenosis; this increased flow was found at the same values of heart rate, left ventricular end-diastolic pressure and perfusion pressure, as those in the preischemic state. Moreover, this increased flow was also observed when the values of peak left ventricular pressure and pressure-length loop area were similar between the pre-ischemic and ischemic states. Thus, contributions of neurohumoral factors or alterations in mechanical factors determining the myocardial oxygen demand and supply relation are negligible. This increased flow may be important in maintaining overall cardiac function in cases of acute coronary stenosis or coronary occlusion.