Regional Distribution of Diffusible Tracers and Carbonized Microspheres in the Left Ventricle of Isolated Dog Hearts

Abstract

Microspheres of different sizes, '-"'I-labeled antipyrine (I-Ap), and 4 -KCl or 86 RbCl were injected into the aortic inflow of isolated, Langendorff, perfused, nonworking dogs hearts at blood flows of 1.3-4.8 ml/min g~'. 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 one heart in which the aortic pressure and the total coronary flow were low. The deposition of ^-K and that of I-Ap were essentially similar in three 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 42 K 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 42 K.

Physiology and theory of tracer washout techniques for the estimation of myocardial blood flow: Flow estimation from tracer washout

“…The technique developed by Yipintsoi et al merits special consideration for use as a standard for estimating heterogeneity. 40 They cut the hearts into four or five slices from apex to base. Each slice of left ventricle was cut into 8 wedges at 45° angles, and each wedge cut into 10-12 sections from endocardium to epicardium, as shown in Fig.…”

Coronary Reserve of High- and Low-Flow Regions in the Dog Heart Left Ventricle

“…However, when analysis of the local deposition density of microspheres [2][3][4][5] and diffusible plasma flow markers [6][7][8] in volume elements of a few millimeters diameter showed that the local flow distribution within individual hearts is markedly heterogeneous, covering a range from 20% to 200% of the mean value. This flow heterogeneity is remarkably stable over periods of several hours, 4 even if the heart is intermittently stimulated.…”

Multiple Injections of Coloured Microspheres for Islet Blood Flow Measurements in Anaesthetised Rats: Influence of Microsphere Size

“…Over the size range of 10-15 m the bias in size of microspheres compared to erythrocytes appears unimportant for most organs (12,13). To avoid the risk of arteriovenous shunting 15 m microspheres have become the standard choice.…”