Significance of performing 123I-metaiodobenzylguanidine myocardial scintigraphy at different times for the long-term prediction of cardiac events in patients with dilated cardiomyopathy

OBJECTIVESAlthough it has been reported that I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy is useful for assessing the prognosis of dilated cardiomyopathy (DCM), there have been no reports regarding how interval MIBG imaging should be performed during follow-up. We investigated the significance of performing MIBG at different times for the long-term prediction of cardiac events in DCM patients. METHODSThe participants were 36 DCM patients who did not sustain cardiac events for 2 years after β-blocker induction. MIBG was performed 6 months and 2 years after β-blocker induction and the images analyzed to obtain the extent score, severity score (SEV), and the washout rate. Echocardiography was performed at the same time. RESULTSEight patients experienced a cardiac event during follow-up (cardiac deathtwo patients; heart failure requiring hospitalizationsix patients). Although no significant difference was found in any MIBG parameters or left ventricular ejection fraction between patients who experienced a cardiac event and those who did not after 6 months, early extent score, early SEV, delayed SEV, and washout rate were found to be significantly higher for patients who experienced a cardiac event after 2 years. In multivariate analysis using Cox proportional hazard model, none of the MIBG parameters or left ventricular ejection fraction after 6 months was identified as a predictor of cardiac events. However, delayed SEV after 2 years (hazard ratio 1.067, P=0.0435) was a significant predictor of cardiac events. CONCLUSIONThe study suggested that performing MIBG at least once every 2 years allows long-term prediction of cardiac events in the follow-up of DCM patients.