Myocardial blood flow and oxygen consumption in the empty-beating, fibrillating, and potassium-arrested hypertrophied canine heart.

Myocardial oxygen consumption and blood flow distribution were examined in severely hypertrophied canine hearts in the empty-beating, fibrillating, and pharmacologically arrested states. Hypertrophy was produced using a subcoronary valvular aortic stenosis model that mimics the clinical situation of aortic valvular stenosis. Oxygen content of the total coronary sinus collection was compared with a large volume arterial sample using a Lex-O2-Con-TL analyzer, which had been validated by the Van Slyke-Neill method. Transmural blood flow was measured in each state using microspheres, and perfusion pressure was maintained at 80 mm Hg. Oxygen consumption in the empty-beating hypertrophied heart was found to be the same as that previously reported for normal hearts. Blood flow was evenly distributed in the empty-beating heart, with an endocardial/epicardial ratio of 0.99 +/- 0.15 (SEM) milliliters per minute per gram of left ventricular weight. Oxygen consumption failed to increase significantly with fibrillation; however, blood flow distribution favored the subepicardium, suggesting that oxygen consumption determinations in the fibrillating hypertrophied heart may not accurately reflect metabolic demand. Basal oxygen consumption of the hypertrophied heart as determined by the potassium-arrested, blood-perfused model was the same as that previously described for normal hearts. Blood flow during potassium arrest favored the subendocardium (endocardial/epicardial ratio = 1.14 +/- 0.27 ml/min/gm LV weight).