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

Abstract.

Accurate assessment of myocardial viability permits selection of patients who would benefit from myocardial revascularization. Currently, rest-redistribution thallium-201 scintigraphy and low-dose dobutamine echocardiography are among the most used techniques for the identification of viable myocardium. Thirty-one consecutive patients (all men, mean age 60±8 years) with chronic coronary artery disease and reduced left ventricular ejection fraction (31%±7%) were studied. Rest ²⁰¹Tl single-photon emission tomography (SPET), low-dose dobutamine echocardiography and radionuclide angiography were performed before revascularization. Radionuclide angiography and echocardiography were repeated after revascularization. An a/dyskinetic segment was considered viable on ²⁰¹Tl 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 significant at ≥5%. In identifying viable segments, rest ²⁰¹Tl SPET showed higher sensitivity than low-dose dobutamine echocardiography (72% vs 53%, P<0.05), while specificity was not significantly different (86% vs 88%). In 17 patients, global ejection fraction increased ≥5% (group 1) while in 14 it did not (group 2). A higher number of a/dyskinetic segments were viable on ²⁰¹Tl SPET in group 1 than in group 2 (2.6±1.9 vs 0.6±1.2, P<0.005), while no significant differences were observed on low-dose dobutamine echocardiography (1.7±1.6 vs 1.1±1.6). A significant correlation was found between the number of a/dyskinetic segments viable on ²⁰¹Tl SPET and post-revascularization changes in ejection fraction (r=0.52, P<0.05), but such a correlation was not observed for low-dose dobutamine echocardiography. Using as the cut-off the presence of at least one viable a/dyskinetic segment, rest ²⁰¹Tl 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%, respectively) as compared with low-dose dobutamine echocardiography. In conclusion, these findings suggest that when severely reduced global function is present, rest ²⁰¹Tl SPET evaluation of viability is more accurate than low-dose dobutamine echocardiography for the identification of patients who will benefit most from revascularization.