Comparison of I-123 IPPA and thallium-201 for the prediction of functional improvement after myocardial revascularization

Sixteen patients in the phase I/II study of IPPA had RRT prior to MR. Patients were injected with 2-6 mCi of IPPA; sequential SPECT imaging was begun at 4 minutes. Radionuclide ventriculography was performed before and 8 weeks after MR. The ability of IPPA and RRT to identify patients with a 5% increase in EF after MR were compared using receiver operating characteristic (ROC) curve analysis. The IPPA images were analyzed using two techniques: The first method looked at the fraction of the myocardium (FM) demonstrating abnormal metabolism and the second at the FM demonstrating descreased initial perfusion and abnormal metabolism. RRT images were analyzed three different ways: Thresholded uptake on the initial images, thresholded uptake on the delayed images and relative improvement between the initial and delayed images. The parameters giving the highest ROC areas were identified for both IPPA and RRT and then compared. Five patients underwent PTCA and 11 underwent coronary artery bypass grafting. The mean EF increased from 36±12% to 41±14% after MR (p=0.012). The amount of myocardium (AM) showing intermediate metabolism (IM) of IPPA from 0.001 to 0.013 In counts/min was a strong predictor of FI after MR (area=0.92±0.05). The AM that was hypoperfused and had IM (activity<90% of maximum uptake and metabolism from 0.002-0.013 In counts/min) was a stronger predictor (area=0.97 0.03). Using RRT, the best predictor was the AM with greater than 55% of maximal activity on the initial images (area=0.83±0.10); the AM>45% of maximal activity on the delayed images was slightly lower (area=0.81±0.10); improvement between the initial and delayed images was comparatively weak (0.56±0.13). The difference between the areas between IPPA and RRT, however, was not statistically significant. (orig./MG)