Inert gas measurements of myocardial perfusion in the presence of heterogeneous flow documented by microspheres.

Publisher Website
Google Scholar
Abstract
Inert gas measurements of flow per unit wt (F/W) incorporating even saturation of heterogeneously perfused areas and 2-decade resolution of coronary venous desaturation curves were compared with radioactive microsphere measurements of F/W in closed-chest dogs with modest heterogeneity of F/W. Coefficients of variation for microsphere measurements in 96 left ventricular segments revealed global heterogeneity of F/W, of similar degree, in dogs with and without an abdominal aortocaval fistula (0.18 .+-. 0.07 vs. 0.15 .+-. 0.04; p > 0.3). Endocardial-epicardial flow ratios were lower in the fistula dogs (0.77 .+-. 0.11 vs. 1.05 .+-. 0.08; p < 0.01), reflecting transmural and nontransmural heterogeneity of F/W. Inert gas measurements of average F/W, derived from the Kety-Schmidt equation using dissolved hydrogen (H2) as tracer, agreed within .+-. 20% of average microsphere F/W in 18 of 20 comparisons in fistula and nonfistula dogs. Semilogarithmically plotted H2 desaturation data were curvilinear in both settings, but arbitrarily derived slow-compartment H2 F/W agreed with average microsphere endocardial F/W only in the fistula dogs. Methodologically adequate inert gas measurements apparently give accurate values for average F/W in the presence of moderate heterogeneity of perfusion and although the presence of heterogeneous perfusion can be appreciated from the shape of inert gas desaturation curves, compartmental analyses of curves cannot ordinarily be interpreted in a specific transmural or other spatial sense.