Long-term prognostic stratification by a combination of ¹²³I-metaiodobenzylguanidine scintigraphy and ejection fraction in dilated cardiomyopathy

¹²³I-metaiodobenzylguanidine (MIBG) scintigraphy is a useful tool for predicting the prognosis in patients with congestive heart failure; however, little is known regarding long-term prognostic evaluations. The aim of this study was to evaluate long-term prognosis in a roughly 10-year period, in dilated cardiomyopathy (DCM) by MIBG imaging, compared to other conventional functional parameters.

Eighty-six DCM patients (50 ± 14 years of age, 57 males) underwent MIBG imaging, at 15 min and 4 h after tracer injection, from which the delayed heart to mediastinum ratio (H/M) and washout rate (WR) were obtained. The left ventricular ejection fraction (EF) and end-diastolic diameter (LVDd) were also measured by echocardiogram. All patients were followed up for 8–14 years, and the death event was investigated.

Kaplan–Meier curves revealed a poor prognosis only in the group above the third quartile of WR (=50%) (10-year prognosis, 35%); however, there were no statistically significant differences in prognosis among the other 3 groups (10-year prognosis, 75–84%). A Cox hazard univariate analysis selected WR (p = 0.0004), H/M (p < 0.0001), EF (p = 0.0024), and LVDd (p = 0.0189) as significant prognostic indicators. Multivariate analysis revealed the H/M (p = 0.0023) and EF (p = 0.024) to be an independent prognostic predictor. The 10-year prognosis of patients with both WR < 50% and EF > 30%; WR < 50% and EF < 30%; and both WR > 50% and EF < 30% were 89, 71, and 33%, respectively. These three groups were well stratified, significantly (log-rank test: χ ² = 30.0, p < 0.0001). However, even patients with WR ≥ 50% had few death events after 3 years following MIBG imaging.

The MIBG parameter, delayed H/M or WR combined with the EF is a useful tool for the prediction of a long-term prognosis in DCM, which is superior to MIBG parameters alone. However, patients with WR > 50% but no event in a 3-year follow-up period should undergo an additional MIBG imaging for prognostic prediction.