Usefulness of 123I-metaiodobenzylguanidine myocardial scintigraphy for predicting the effectiveness of β-blockers in patients with dilated cardiomyopathy from the standpoint of long-term prognosis

Purpose: The usefulness of I-123-metaiodobenzylguanidine (MIBG) myocardial scintigraphy in predicting the effectiveness of beta-blocker therapy in dilated cardiomyopathy (DCM) was investigated from the standpoint of long-term prognosis. Methods: The subjects were 53 DCM patients in whom beta-blockers had been successfully introduced and used for 6 months or longer. When symptoms were stable before the introduction of beta-blockers and for up to 1 year thereafter, MIBG myocardial single-photon emission computed tomography was performed and the images analysed to obtain the extent score (EXT), severity score (SEV) and washout rate (WR). At the same time, echocardiography was performed to measure left ventricular ejection fraction (LVEF). Thereafter, patients were placed under observation for an average of 1,314+/-986 days, with the occurrence of cardiac events as the endpoint. Results: The degree of improvement in WR after introduction of beta-blockers was a significant predictor of cardiac events. In fact, none of the patients whose improvement in WR was valued at 10 or higher had cardiac events. Accordingly, using improvement in WR of 10 as the cut-off value, the patients were divided into two groups, "improved" and "unimproved". There were significant differences between the groups in respect of early EXT, early SEV and WR before the introduction of beta-blockers . As regards predictors of WR improvement, multivariate logistic regression analysis demonstrated that early EXT, WR and LVEF were significant predictors. Conclusion: This study shows that, from the standpoint of long-term prognosis, DCM patients who would benefit the most from beta-blocker therapy are those with low early EXT and early SEV and high WR before beta-blocker introduction regardless of LVEF values.