Tissue blood flow to the heart. Influence of coronary occlusion and surgical measures.

• Many surgical procedures designed to increase the total blood flow to the heart or to distribute the existing flow more equitably have been proposed. 1 " 3 The assessment of these operations has been hampered in the past by: (1) difficulty in obtaining objective data from clinical patients, (2) lack of a method to measure capillary (tissue) blood flow to specific areas of myocardium, and (3) lack of a method to measure quantitatively and selectively the functional blood flow to the heart before and after coronary occlusion and after attempts at revascularization. In the present study, tissue blood flow to specific regions of the canine heart was measured utilizing the deuterium oxide method. 4 " 6 The influence of coronary occlusion and of two operative procedures on regional blood flow was quantitated. Methods All experiments were performed on healthy, adult mongrel dogs of either sex, anesthetized with sodium pentobarbital (30 mg./Kg.). Per-fusion of coronary vessels was performed in situ via, a catheter placed in the ascending aorta advanced from the right carotid and brachio-cephalic arteries. Tapes were placed about the superior and inferior venae cavae and about thp brachiocephalic artery. Occlusion of the aorta immediately distal to the brachipcephalic artery was provided by a surgical clamp. A collecting catheter was placed in the ostium of the coronary sinus and fixed in place with a purse-string suture. At the beginning of the experiment, inflow occlu-sion was established by occluding the venae cayae; following this, coronary perfusion was started using oxygenated blood at 37 C. from a pressure flask. (135 mm. Hg). The tape about the brachiocephalic artery was drawn up and the clamp placed about the aorta immediately beyond the brachiocephalic artery, thereby limiting perfu-sion to the coronary system. Following an initial period of equilibration of the isolated beating heart with nonlabeled perfusion fluid (blood), the inflow was changed to blood containing 2 volume per cent deuterium oxide.* The perfusion with blood-D 2 O mixture was discontinued after 20 to 30 seconds. The heart was removed, and the blood was allowed to drain from the cut vessels and was blotted dry and weighed. Seven tissue pieces weighing 2 to 3 6m. were taken from the right ventricle and the left ventricle in the distribution of the left anterior descending and the circumflex coronary arteries. The tissues and samples of the perfusing blood were prepared for D 2 O analysis by …