Microheterogeneity of regional myocardial blood flows in low-perfused rat hearts evaluated by double-tracer digital radiography.
Using (3)H- and (125)I-labeled desmethylimipramine (DMI) for regional flow tracers, we established a two-time measurement method for the spatial pattern of myocardial perfusion in cross-circulated rat hearts. Myocardial extractions and retentions of these tracers were confirmed to be satisfactory; however, the latter were less than 90% after 3 min at a perfusion rate of 2.9 ml/min/g, limiting the present application to a short-time perfusion measurement. Distributions of myocardial depositions were separated by subtraction digital radiography with 400-microm pixel resolution. Its feasibility was examined by regression analysis between local deposition densities of (3)H- and (125)I-DMI injected simultaneously. The slope, y-intercept, and correlation coefficient (r) of the regression line were 0.98+/-0.04, 0.02+/-0.04, and 0.95+/-0.03, respectively, indicating the validity of the present image subtraction technique. The spatial pattern of myocardial perfusion in response to flow reduction was evaluated by the injections of (3)H- and (125)I-DMI, respectively, before and after a nearly 70% flow reduction. A significant correlation between normalized density distributions of these tracers was found in both subepicardium (r=0.77+/-0.12) and subendocardium (r=0.73+/-0.20), indicating the stable pattern of myocardial perfusion. However, the coefficient of variation of tracer densities showed a decrease of subendocardial flow heterogeneity from 35+/-15% to 31+/-16%. Thus, flow differences between originally high- and low-flow regions in subendocardium were reduced on a relative basis during low perfusion.
Matsumoto
Takeshi
T
Bioengineering Division, Osaka University Graduate School of Engineering Science, Machikaneyamacho 13, Toyonaka 5608531, Japan. matsu@me.es.osaka-u.ac.jp
Asano
Takahisa
T
Takemoto
Mami
M
Tachibana
Hiroyuki
H
Ogasawara
Yasuo
Y
Kajiya
Fumihiko
F
D000818:Animals; D001345:Autoradiography / Q000379:methods*; D003326:Coronary Circulation / Q000502:physiology*; D003891:Desipramine; D003903:Deuterium; D007457:Iodine Radioisotopes; D010477:Perfusion / Q000379:methods; D011856:Radiographic Image Enhancement / Q000379:methods*; D051381:Rats; D012680:Sensitivity and Specificity
D007457:Iodine Radioisotopes; D003903:Deuterium; D003891:Desipramine