Microspheres of different sizes, 125I labeled antipyrine (I Ap), and 42KCl or 86RbCl were injected into the aortic inflow of isolated, Langendorff, perfused, nonworking dogs hearts at blood flows of 1.3-4.8 ml/min g-1. After 15 seconds to 5 minutes, the left ventricle was sectioned into about 300 ordered pieces, and the amount of each tracer was determined. For all tracers, the relative density of deposition was generally higher in the endocardial region, except in 1 heart in which the aortic pressure and the total coronary flow were low. The deposition of 42K and that of I Ap were essentially similar in 3 hearts over a large range of regional variation. This finding suggests either that both tracers were distributed in proportion to flow or that a small diminution in relative density of deposition of 42K in high flow regions due to lower transcapillary extraction was quantitatively similar to a decrease in the residual fraction of I Ap in these same regions due to faster washout in the first 15-30 seconds after injection. Large microspheres were deposited preferentially in regions of high flow, exaggerating the apparent heterogeneity of regional flows. The distribution of the smaller microspheres was closer to that for I Ap or 42K.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine