Discrepancy between microsphere and diffusible tracer estimates of perfusion to ischemic myocardium
Yoshida, S.; Akizuki, S.; Gowski, D.; Downey, J.M.
American Journal of Physiology 249(2 Pt 2): H255-H264
1985
ISSN/ISBN: 0002-9513 PMID: 3895981 Document Number: 250012
This study critically tests the ability of microspheres to accurately measure perfusion to ischemic myocardium . The left anterior descending coronary artery was cannulated and perfused with arterial blood. The perfusion line was clamped, and a sidearm between the clamp and the cannula was opened to the atmosphere, allowing blood to flow retrograde form the distal segment of the artery. Measurement of regional blood flow during retrograde flow diversion with 15-.mu.m microspheres revealed essentially zero flow to the perfused segment (0.005 ml .cntdot. min-1 .cntdot. g-1). Measurements under the same conditions by either 86Rb uptake of 133Xe washout revealed that an appreciable perfusion of the tissue persisted during retrograde flow diversion (0.043 and 0.11 ml .cntdot. min-1 .cntdot. g-1, respectively, for the 2 methods). Thus, a condition during which microspheres indicate zero flow to the tissue but diffusible tracers can both be washed in and washed out at a brisk rate. With simple occlusion there apparently is a hidden component of perfusion to an ischemic zone that cannot be measured by microspheres, caused them to underestimate flow by .apprx. 25% in that condition.