AJP - Heart and Circulatory Physiology, Vol 244, Issue 1 121-H130, Copyright © 1983 by American Physiological Society
Stability of 8-, 15-, and 26-micron microspheres entrapped in feline myocardium
K. S. Andersen, R. Skjerven and J. Lekven
The stability of 8-, 15-, and 26-micron radioactive microspheres entrapped
in ischemic and nonischemic myocardium and possible mechanisms for
microsphere loss were investigated. Anesthetized cats were given
microspheres prior to left anterior descending coronary artery occlusion
(or sham operation) and 8 h later. Eight-micron microspheres, compared with
15-micron spheres, underestimated preocclusion myocardial blood flow in
ischemic and nonischemic tissue by 30%. With 26-micron spheres,
endocardial-to-epicardial blood flow ratio was 1.28. In nonischemic tissue,
no loss of 15- and 26-micron microspheres occurred during 8 h. In ischemic
myocardium, however, 15% apparent loss of 15- and 26-micron preocclusion
spheres took place. In endocardial ischemic tissue, edema could account for
50% of the 15-micron microsphere loss and almost completely for loss of
26-micron spheres. In epicardial ischemic tissue, microsphere loss was not
influenced by edema. We found no hemodynamic variable that could predict
the magnitude of microsphere loss. Only weak evidence for migration of 15-
and 26-micron microspheres through lymphatic pathways was found. Most
likely the spheres migrated through venous pathways to embolize in the
lungs. We conclude that 15-micron microspheres provide the most reliable
tissue blood flow estimates in normal myocardium, but even for these
spheres significant loss occurs during 8 h of ischemia.
