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Abstract
BackgroundPerformance of the left ventricle during exercise stress in thalassaemia patients is uncertain. We aimed to explore the phenomenon of dynamic dyssynchrony and assess contractile reserve in patients with beta-thalassaemia major and determine their relationships with myocardial iron load.Methods and ResultsThirty-two thalassaemia patients (16 males), aged 26.8±6.9 years, without heart failure and 17 healthy controls were studied. Their left ventricular (LV) volumes, ejection fraction, systolic dyssynchrony index (SDI), and myocardial acceleration during isovolumic LV contraction (IVA) were determined at rest and during submaximal bicycle exercise testing using 3-dimensional and tissue Doppler echocardiography. Myocardial iron load as assessed by T2* cardiac magnetic resonance in patients were further related to indices of LV dyssynchrony and contractile reserve. At rest, patients had significantly greater LV SDI (p<0.001) but similar IVA (p = 0.22) compared with controls. With exercise stress, the prevalence of mechanical dyssynchrony (SDI>4.6%, control+2SD) increased from baseline 25% to 84% in patients. Δ SDIexercise-baseline correlated with exercise-baseline differences in LV ejection fraction (p<0.001) and stroke volume (p = 0.006). Compared with controls, patients had significantly less exercise-induced increase in LV ejection fraction, cardiac index, and IVA (interaction, all p<0.05) and had impaired contractile reserve as reflected by the gentler IVA-heart rate slope (p = 0.018). Cardiac T2* in patients correlated with baseline LV SDI (r = −0.44, p = 0.011) and IVA-heart rate slope (r = 0.36, p = 0.044).ConclusionsResting LV dyssynchrony is associated with myocardial iron load. Exercise stress further unveils LV dynamic dyssynchrony and impaired contractile reserve in patients with beta-thalassaemia major.
Highlights
Iron-induced cardiomyopathy is well documented in patients with beta-thalassaemia major [1]
Resting left ventricular (LV) dyssynchrony is associated with myocardial iron load
Dynamic mechanical dyssynchrony [2] and impaired contractile reserve [3] of the left ventricle during exercise stress have been demonstrated in patients with idiopathic and secondary cardiomyopathies
Summary
Iron-induced cardiomyopathy is well documented in patients with beta-thalassaemia major [1]. In the unmasking of subtle ventricular dysfunction, the role of exercise stress is increasingly acknowledged. Dynamic mechanical dyssynchrony [2] and impaired contractile reserve [3] of the left ventricle during exercise stress have been demonstrated in patients with idiopathic and secondary cardiomyopathies. Studies of left ventricular (LV) function in thalassaemia patients have primarily been performed during resting condition. In patients with beta-thalassaemia major, substrate for development of LV dynamic dyssynchrony potentially exists. Performance of the left ventricle during exercise stress in thalassaemia patients is uncertain. We aimed to explore the phenomenon of dynamic dyssynchrony and assess contractile reserve in patients with beta-thalassaemia major and determine their relationships with myocardial iron load
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