Prediction of improvement in global left ventricular function in patients with chronic coronary artery disease and impaired left ventricular function: rest thallium-201 SPET versus low-dose dobutamine echocardiography

Accurate assessment of myocardial viability permits selection of patients w ho would benefit from myocardial revascularization. Currently, rest-redistr ibution thallium-201 scintigraphy and low-dose dobutamine echocardiography are among the most used techniques for the identification of viable myocard ium. Thirty-one consecutive patients (all men, mean age 60 +/- 8 years) wit h chronic coronary artery disease and reduced left ventricular ejection fra ction (31% +/- 7%) were studied. Rest Tl-210 single-photon emission tomogra phy (SPET), low-dose dobutamine echocardiography and radionuclide angiograp hy were performed before revascularization. Radionuclide angiography and ec hocardiography were repeated after revascularization. An a/dyskinetic segme nt was considered viable on Tl-201 SPET when tracer uptake was >65%, while improvement on low-dose dobutamine echocardiography was considered a marker of viability. Increase in global ejection fraction was considered signific ant at greater than or equal to5%. In identifying viable segments, rest Tl- 201 SPET showed higher sensitivity than low-dose dobutamine echocardiograph y (72% vs 53%, P < 0.05). While specificity was not significantly different (86% vs 88%). In 17 patients, global ejection fraction increased <greater than or equal to>5% (group I) while in 14 it did not (group 2). A higher nu mber of a/dyskinetic segments were viable on Tl-201 SPET in group I than in group 2 (2.6 +/- 1.9 vs 0.6 +/- 1.2, P < 0.005). while no significant diff erences were observed on low-dose dobutamine echocardiography (1.7 <plus/mi nus> 1.6 vs 1.1 +/- 1.6). A significant correlation was found between the n umber of a/dyskinetic segments viable on Tl-201 SPET and post-revasculariza tion changes in ejection fraction (r = 0.52, P < 0.05), but such a correlat ion was not observed for low-dose dobutamine echocardiography. Using as the cut-off the presence of at least one viable a/dyskinetic segment, rest Tl- 201 SPET had a higher sensitivity (82% vs 53%, P = 0.07) and showed a trend towards higher accuracy and specificity (77% vs 58%, and 71% vs 64%, respe ctively) as compared with low-dose dobutamine echocardiography. In conclusi on, these findings suggest that when severely reduced global function is pr esent, rest Tl-201 SPET evaluation of viability is more accurate than low-d ose dobutamine echocardiography for the identification of patients who will benefit most From revascularization.