The present study aimed to identify the clinical significance of differences in detection timings of left ventricular reverse remodeling (LVRR) on heart failure (HF) prognosis in patients with idiopathic dilated cardiomyopathy (IDCM). We investigated 207 patients with IDCM who underwent pharmacotherapeutic treatment. LVRR was defined as improvements in both LV ejection fraction ≥10 % and indexed LV end-diastolic dimension (LVEDDi) ≥10 %. Patients were stratified into 3 groups by LVRR timing: patients with LVRR <24 months (Early LVRR), those with LVRR ≥24 months (Delayed LVRR), and those without LVRR during the entire follow-up period (No LVRR). The major endpoint was first detection of composite event including readmission for decompensated HF, major ventricular arrhythmias, or all-cause mortality. LVRR was recognized in 108 patients (52 %): Early LVRR in 83 (40 %), Delayed LVRR in 25 (12 %), and No LVRR in 99 (48 %). The survival rate for the major endpoint was significantly higher for Delayed LVRR than for No LVRR (P = 0.001); there was no significant difference between Early and Delayed LVRR. Among patients without LVRR <24 months (Delayed + No LVRR), receiver operating characteristic curve analysis showed that the area under the curve for improvement in LVEDDi during the first 6 months for predicting subsequent LVRR (Delayed LVRR) [0.822 (95 % confidence interval, 0.740–0.916; P = 0.038)] was greater than that for improvement in LVEF. In conclusion, LVRR was a favorable prognostic indicator in patients with IDCM irrespective of its detection timing. Reduced LVEDDi during the first 6 months was predictive for subsequent LVRR in the later phase.
