ABSTRACT
UNLABELLED: The goals of this investigation were to assess the accuracy of (18)F-fluorodihydrorotenone ((18)F-FDHR) as a new deposited myocardial flow tracer and to compare the results to those for (201)Tl. METHODS: The kinetics of these flow tracers in 22 isolated, erythrocyte- and albumin-perfused rabbit hearts were evaluated over a flow range encountered in patients. The 2 flow tracers plus a vascular reference tracer ((131)I-albumin) were introduced as a bolus through a port just above the aortic cannula. Myocardial extraction, retention, washout, and uptake parameters were computed from the venous outflow curves with the multiple-indicator dilution technique and spectral analysis. RESULTS: The mean +/- SD initial extraction fractions for (18)F-FDHR (0.85 +/- 0.07) and (201)Tl (0.87 +/- 0.05) were not significantly different, although the initial extraction fraction for (18)F-FDHR declined with flow (P < 0.0001), whereas the initial extraction fraction for (201)Tl did not. The washout of (201)Tl was faster (P < 0.001) and more affected by flow (P < 0.05) than was the washout of (18)F-FDHR. Except for the initial extraction fraction, (18)F-FDHR retention was higher (P < 0.001) and less affected by flow (P < 0.05) than was (201)Tl retention. Reflecting its superior retention, the net uptake of (18)F-FDHR was better correlated with flow than was that of (201)Tl at both 1 and 15 min after tracer introduction (P < 0.0001 for both comparisons). CONCLUSION: The superior correlation of (18)F-FDHR uptake with flow indicates that it is a better flow tracer than (201)Tl in the isolated rabbit heart. Compared with the other currently available positron-emitting flow tracers ((82)Rb, (13)N-ammonia, and (15)O-water), (18)F-FDHR has the potential of providing excellent image resolution without the need for an on-site cyclotron.
Subject(s)
Coronary Circulation , Coronary Vessels/diagnostic imaging , Coronary Vessels/metabolism , Rotenone/analogs & derivatives , Rotenone/pharmacokinetics , Thallium/pharmacokinetics , Animals , Image Interpretation, Computer-Assisted , In Vitro Techniques , Kinetics , Male , Metabolic Clearance Rate , Positron-Emission Tomography , Rabbits , Radioisotope Dilution TechniqueABSTRACT
The purpose of this study was to evaluate flow heterogeneity and impaired reflow during reperfusion after 60-min global no-flow ischemia in the isolated rabbit heart. Radiolabeled microspheres were used to measure relative flow in small left ventricular (LV) segments in five ischemia + reperfused hearts and in five nonischemic controls. Relative flow heterogeneity was expressed as relative dispersion (RD) and computed as standard deviation/mean. In postischemic vs. preischemic hearts, RD was increased for the whole LV (0.92 +/- 0.41 vs. 0.37 +/- 0.07, P < 0.05) as well as the subendocardium (Endo) and subepicardium considered separately (1.28 +/- 0.74 vs. 0.30 +/- 0.09 and 0.69 +/- 0.22 vs. 0.38 +/- 0.08; P < 0.05 for both comparisons, respectively) during early reperfusion. During late reperfusion, the increased RD for the whole LV and Endo remained significant (0.70 +/- 0.22 vs. 0.37 +/- 0.07 and 1.06 +/- 0.55 vs. 0.30 +/- 0.09; P < 0.05 for both comparisons, respectively). In addition to the increase in postischemic flow heterogeneity, there were some regions demonstrating severely impaired reflow, indicating that regional ischemia can persist despite restoration of normal global flow. Also, the relationship between regional and global flow was altered by the increased postischemic flow heterogeneity, substantially reducing the significance of measured global LV reflow. These observations emphasize the need to quantify regional flow during reperfusion after sustained no-flow ischemia in the isolated rabbit heart.
