Prediction of the response to beta-blocker therapy in patients with dilated cardiomyopathy: comparison of 123I-MIBG scintigraphy and low-dose dobutamine stress echocardiography.

ABSTRACT

BACKGROUND: In this study, we aimed to compare low-dose dobutamine stress echocardiography (DSE) and iodine 123-metaiodobenzylguanidine (MIBG) scintigraphy for predicting the response to beta-blocker therapy in patients with dilated cardiomyopathy (DCM). METHODS: MIBG imaging was performed in 10 patients with DCM (mean EF 28 ± 8%), who were subsequently treated with beta-blocker therapy. The heart-to-mediastinum (H/M) MIBG uptake ratio was evaluated in initial and delayed images, and the percent washout ratio of myocardial MIBG was determined. DSE was also performed in all patients to measure left ventricular ejection fraction (LVEF) at rest and during dobutamine infusion (10 µg/kg/min). LVEF at rest was also assessed by echocardiography before and after 6 months of beta-blocker therapy. RESULTS: LVEF was significantly improved after beta-blocker therapy (28 ± 8 to 41 ± 11%, p < 0.001). The relative change in LVEF after beta-blocker therapy was significantly correlated with the relative change in LVEF during DSE (r = 0.68, p < 0.03). The H/M MIBG uptake ratio in both early and delayed imaging was not significantly correlated with the relative change in LVEF in response to beta-blockade therapy. CONCLUSIONS: The relative change in LVEF during DSE, but not MIBG imaging predicted the relative change in LVEF in response to beta-blockade therapy in a limited number of DCM patients.