Abstract

both control conditions and ischemia-induced vasodil-atation was studied in eight chronically instrumented awake dogs. Seven of these animals had coarctation-banding ofthe ascending aorta performed at 6 wk of age, and the other dog had congenital subvalvular aortic stenosis. The mean left ventricular weight for the group was 157±7.6 g, and the left ventricular body weight ratio was 8.76+0.47 g/kg. None ofthe animals exhibited signs of congestive heart failure. During the control state, the mean left ventricular systolic pressure was 249+12 mm Hg and the left ventricular end-diastolic pressure was 11.5±0.5 mm Hg. The aortic diastolic pressure was 74±6 mm Hg. Mean left circumflex coronary artery blood flow was 71±6 cm3/min. In the animals with coarctation-band-ing, 52±6 % of the flow occurred during systole. In the dog with congenital subvalvular aortic stenosis, 5 % of the coronary flow was systolic. Mean transmural blood flow during resting conditions was 0.97±0.08 cm3/min per g, and the ratio of endocardial to epicar-dial flow (endo/epi) was 0.88±0.07. During reactive hyperemia, the mean transmural blood flow increased to 3.5±0.30 cm3/min per g; however, the endo/epi decreased to 0.52±0.06. These studies document a difference in transmural blood flow distribution between the normal and the hypertrophied left ventricle: during resting conditions, in the normal ventricle, the highest flow occurs in the endocardial layer, whereas in the hypertrophied ven-tricle, the highest flow is in the middle layers with the endocardial flow less than the epicardial flow.