Impaired Cardiac Sympathetic Innervation Increases the Risk of Cardiac Events in Heart Failure Patients with Left Ventricular Hypertrophy and Mechanical Dyssynchrony

Abstract

Background. Left ventricular mechanical dyssynchrony (LVMD), left ventricular hypertrophy, and impaired cardiac sympathetic innervation are closely related to the development of heart failure (HF) and unfavorable outcomes. Methods and Results. A total of 705 consecutive HF patients with reduced left ventricular ejection fraction (EF) < 50% were registered in our hospital HF database. LVMD and left ventricular mass index (LVMI) were evaluated three-dimensionally by gated myocardial perfusion SPECT. LVMD was measured as a heterogeneity index (phase SD) of the regional contraction phase angles calculated by Fourier analysis. Cardiac sympathetic innervation was quantified as a normalized heart-to-mediastinum ratio (HMR) of the 123I-metaiodobenzylguanidine (MIBG) activity. The patients were followed up with a primary end point of lethal cardiac events (CEs) for 42 months. CEs were documented in 246 of the HF patients who had a greater phase SD, greater LVMI, and lower MIBG HMR than those in HF patients without CEs. In the overall multivariate analysis, phase SD, LVMI, and MIBG HMR were identified as significant CE determinants. The three biomarkers were incrementally related to increases in CE risks. Conclusions. Assessment of cardiac sympathetic innervation can further stratify patients with systolic heart failure at increased cardiac risk identified by left ventricular hypertrophy and mechanical dyssynchrony.