Coronary Microvascular Dysfunction and Adverse Outcomes in the Spectrum of Dilated Cardiomyopathy.

Hypokinetic non-dilated cardiomyopathy (HNDC), a preclinical state of dilated cardiomyopathy (DCM), is characterized by left ventricular (LV) dysfunction without LV dilatation. Although myocardial fibrosis and microvascular dysfunction in DCM are associated with LV remodeling and poor outcome, these characteristics concerning HNDC remain unclear. We compared DCM and HNDC with regard to their clinical characteristics and prognosis.We retrospectively enrolled 100 patients with DCM (n = 64) or HNDC (n = 36) who underwent cardiac magnetic resonance (CMR). DCM and HNDC were classified based on an LV end-diastolic diameter index (LVEDDI). The association of LVEDDI with the composite outcome of all-cause mortality, heart failure hospitalization, or ventricular arrhythmia occurrence was assessed. Phase-contrast cine imaging was performed in a subset of 17 patients (12 with DCM and 5 with HNDC) and 7 control subjects to assess coronary flow reserve (CFR).During the follow-up period (median: 22.0 months; interquartile range: 9.0-33.8 months), patients with DCM showed higher risk of the primary outcome than those with HNDC (P = 0.026). A higher LVEDDI was significantly associated with clinical outcomes even after adjusting for covariates (i.e., brain natriuretic peptide, the presence of late gadolinium enhancement, and LV ejection fraction; adjusted hazard ratio, 1.350; 95% confidence interval, 1.008-1.808; P = 0.044). CFR in HNDC was significantly higher than that in DCM (P < 0.05) and comparable to that in the control group.LV dilatation is an independent predictor of adverse events in DCM and HNDC.