Myocardial iron load in patients with beta-thalassaemia major is associated with global left ventricular mechanical dyssynchrony

Abstract

BACKGROUND: Dyssynchronous contraction of the left ventricular (LV) myocardium is increasingly recognized as an important factor that may contribute to global LV systolic dysfunction. This study aimed to test the hypothesis that myocardial iron overloading in patients with beta-thalassaemia major is associated with LV dyssynchrony, which may contribute to global LV systolic dysfunction. METHODS: We studied 38 thalassaemia patients aged 25.1±6.5 years without heart failure and 20 age-matched healthy controls. Real-time 3-dimensional echocardiography was performed to assess LV volumes, ejection fraction, and mechanical dyssynchrony as quantified by the systolic dyssynchrony index (SDI). The 16-segment SDI was derived from the dispersion of time-to-minimum regional volume, expressed as % of cardiac cycle duration. Relationships between SDI and indices of LV systolic function, myocardial iron load as assessed by T2* cardiac magnetic resonance, and carotid arterial stiffness were further determined in patients. RESULTS: Compared with controls, patients had significantly greater LV SDI (5.0±1.0% vs 3.4±0.7%, p<0.001). Mechanical dyssynchrony (SDI>4.8%, control+2SD), documented in 47% of patients, was associated with increased myocardial iron load (p=0.002), reduced LV ejection fraction (p=0.003), lower global LV longitudinal systolic strain (p=0.04), and increased arterial stiffness (p=0.011). Logistic regression identified T2* (p=0.021) and LV ejection fraction (p=0.017) as significant correlates of LV SDI. CONCLUSIONS: Global LV mechanical dyssynchrony occurs with a relatively high prevalence in patients with beta-thalassaemia major and is associated with myocardial iron overload, worse global LV systolic function, and systemic arterial stiffening.