IDENTIFICATION OF VIABLE MYOCARDIUM IN PATIENTS WITH CHRONIC CORONARY-ARTERY DISEASE USING REST-REDISTRIBUTION TL-201 TOMOGRAPHY - OPTIMAL IMAGE-ANALYSIS

With the widely used 50% threshold, sensitivity is high, but specifici ty is low in detecting viable myocardium on Tl-201 SPECT, In this stud y, we sought to identify the best threshold for semiquantitative Tl-20 1 analysis, Methods: Rest-redistribution Tl-201 SPECT was performed in 46 patients with chronic coronary artery disease before and after myo cardial revascularization, Regional function was evaluated by two-dime nsional echocardiography before and after myocardial revascularization using a 3-point scale (1 = normal, 2 = hypokinetic, 3 = a/dyskinetic) , Myocardial segments with abnormal systolic function were defined as viable if the systolic function score decreased greater than or equal to 1 after myocardial revascularization, A second group of 12 patients with chronic coronary artery disease constituted the validation popul ation. Sensitivity-specificity curves, as well as receiver operating c haracteristic curves, for rest and redistribution images were generate d by varying the Tl-201 uptake threshold. Results: A 65% threshold upt ake using resting images was found to be the best for detecting a/dysk inetic segments that improve after myocardial revascularization from t hose that do not improve. Sensitivity was lower with a 65% threshold ( 75%) than with a 50% threshold (90%, p < 0.05), but specificity was hi gher (76% versus 26%, p < 0.05) resulting in better accuracy (76% vers us 57%, p < 0.05) and positive predictive value (77% versus 55%), whil e the negative predictive value was not different (69% versus 75%, p n ot significant). The area under the receiver operating characteristic curve was significantly (p < 005) larger for rest (0.80 +/- 0.05) as o pposed to redistribution (0.72 +/- 0.05) images. Similar results were obtained in a subgroup of patients with low ejection fraction. Signifi cant correlations between the percentage of revascularized viable segm ents and both the change in ejection fraction and in postrevasculariza tion ejection fraction were found. When these findings were applied in the validation group, a gain in specificity accuracy and positive pre dictive value was obtained with the 65% threshold compared with the 50 % threshold. Conclusion: This study demonstrated that analysis of rest ing images and use of the 65% Tl-201 uptake threshold is preferable fo r separating viable from not viable dyssynergic myocardial segments in patients with chronic coronary artery disease.