Abstract
Distribution of coronary blood flow across the left ventricular wall (LVW) is known to be affected by such factors as intra- and extravascular coronary resistance and coronary arterial perfusion pressure. The present experiments were designed to measure and compare the distribution of coronary blood flow across the LVW in the isolated, vented, metabolically supported canine heart during conditons of abolished coronary autoregulation by adenosine infusion. Total coronary blood flow was measured by an electromagnetic flowmeter in the inflow line while regional coronary flow distribution was determined in eight tissue layers across the LVW from the subepicardial (Epi) to subendocardial (Endo) surfaces by the tracer microsphere (TM) technique. The microspheres employed were of either 8–10μ diameter and were best characterized as a parabolic function of wall depth. This function could be labelled with Sr-85, Ce-141, Cr-51, or Sc-46, or of 15 μ diameter and labelled with I-125 or Nb-95. Each TM injection contained approximately 200,000 microspheres and was administered into the arterial perfusion line about 20 cm from the aortic root to ensure good mixing. Tissue preparation and nuclide counting techniques were similar to those previously described (8) except that samples of myocardium were divided into eight layers across the LVW.
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