QUANTITATIVE PLANAR REST-REDISTRIBUTION TL-201 IMAGING IN DETECTION OF MYOCARDIAL VIABILITY AND PREDICTION OF IMPROVEMENT IN LEFT-VENTRICULAR FUNCTION AFTER CORONARY-BYPASS SURGERY IN PATIENTS WITH SEVERELY DEPRESSED LEFT-VENTRICULAR FUNCTION

Background. Although many patients with multivessel coronary artery disease (CAD) and severely depressed left ventricular (LV) function will benefit from coronary artery bypass graft surgery (CABG), surgeons may be reluctant to perform CABG on these patients without evidence of myocardial viability in regions of severe asynergy. We hypothesized that quantitative planar rest-redistribution Tl-201 imaging would identify viable myocardium and predict improved regional and global function after revascularization in patients with depressed LV function and CAD. Methods and Results. Twenty-one patients (mean LV ejection fraction, 0.27+/-0.05) were studied. Regional and global LV functions were evaluated before and 8 weeks after CABG with radionuclide ventriculography. Segments were prospectively classified as showing normal, mildly reduced, or severely reduced viability on the basis of quantitative analysis of defect severity and redistribution on planar resting Tl-201 imaging. By Tl-201 criteria, 90% of hypokinetic segments were classified with normal or mildly reduced viability. Among akinetic or dyskinetic segments, 20% had normal Tl-201 uptake, 53% had mildly reduced viability, and only 27% had severely reduced viability. Tl-201 viability criteria identified segments that improved function after CABG. Sixty-two percent of severely asynergic segments with normal viability and 54% with mildly reduced viability improved function after surgery, but only 23% with severely reduced viability improved function (p=0.002). When only adequately revascularized segments were considered, the predictive value of a positive preoperative viability scan for functional improvement was 73%. The greatest improvement in global LV function after CABG occurred in patients with the greatest number of asynergic segments classified as viable before surgery (p<0.01). In 10 patients with more than seven viable, asynergic segments, mean LV ejection fraction increased significantly after CABG (0.29+/-0.07 to 0.41+/-0.11, p=0.002). In 11 patients with seven or fewer viable, asynergic segments, mean LV ejection fraction remained unchanged after revascularization (0.27+/-0.05 to 0.30+/-0.08, p=NS). Conclusions. In patients with CAD and severely depressed LV function, preoperative quantitative planar rest-redistribution Tl-201 imaging identifies viability in many asynergic myocardial segments, and these segments frequently improve function after CABG. The presence of numerous asynergic but viable myocardial segments before surgery correlated significantly with improvement in global LV function after bypass surgery.