Head-to-head comparison of exercise-redistribution-reinjection thallium single-photon emission computed tomography and low dose dobutamine echocardiography for prediction of reversibility of chronic left ventricular ischemic dysfunction
OBJECTIVES: We sought to directly compare the diagnostic value of exercise-redistribution-reinjection thallium single-photon emission computed tomography (SPECT) and low dose dobutamine echocardiography for prediction of contractile recovery after revascularization. BACKGROUND: Both thallium SPECT and dobutamine echocardiography have been proposed to predict the reversibility of left ventricular dysfunction after revascularization. Although both techniques permit differentiation of viable from nonviable myocardium, few studies have directly compared their accuracy in the same patients. METHODS: Seventy-three consecutive patients (mean [+/- SD] age 59 +/- 9 years) with coronary disease and regional left ventricular dysfunction underwent exercise-redistribution-reinjection thallium SPECT and dobutamine echocardiography before revascularization. Recovery of function was evaluated with echocardiography 5.5 +/- 2.5 months after revascularization. For analysis, the left ventricle was divided into 16 segments, in which percent thallium uptake was quantitated using circumferential profiles, and regional wall motion was graded semiquantitatively (normal = 1; akinetic = 3). RESULTS: The diagnostic performance of the two tests was investigated both for individual patients and for individual segments. Individual patient analysis showed that left ventricular ejection fraction improved > 5% after revascularization in 43 patients, whereas 30 showed no change. Receiver operating characteristic curves were used to select optimal criteria for prediction of functional recovery after revascularization. According to a mean thallium uptake > 54% at reinjection, SPECT had a sensitivity of 72%, a specificity of 73% and an overall accuracy of 73%. Similarly, according to an improvement in wall motion score > 3.5 grades during doubutamine echocardiography, echocardiography had a sensitivity of 88%, a specificity of 77% and an overall accuracy of 84% (p = NS vs. thallium). Segmental analysis showed that SPECT and dobutamine echocardiography had similar sensitivity (77% and 75%, respectively), but SPECT had lower specificity (56% vs. 86%, p < 0.01). CONCLUSIONS: Quantitative exercise-redistribution-reinjection thallium SPECT and dobutamine echocardiography have comparable accuracy for prediction of reversibility of global left ventricular dysfunction after revascularization. However, dobutamine echocardiography has greater specificity than thallium imaging for prediction of functional recovery on a segmental basis.