Division of Paediatric Cardiology, Queen Mary Hospital, The University of Hong Kong, Hong Kong, China.
PLoS One. 2012;7(9):e45265. doi: 10.1371/journal.pone.0045265. Epub 2012 Sep 18.
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.
Thirty-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 SDI(exercise-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).
Resting 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.
运动应激下左心室在珠蛋白生成障碍性贫血患者中的功能尚不确定。我们旨在探讨运动应激下左心室的运动不同步现象，并评估重型β地中海贫血患者的收缩储备功能及其与心肌铁负荷的关系。
32 例（男 16 例）年龄 26.8±6.9 岁的重型β地中海贫血患者，无心力衰竭，17 例健康对照者纳入研究。采用三维和组织多普勒超声心动图在静息和次最大踏车运动试验时测量左心室（LV）容积、射血分数、收缩期不同步指数（SDI）和等容左室收缩期心肌加速度（IVA）。进一步将患者的心肌铁负荷通过心脏 T2磁共振评估与 LV 不同步和收缩储备的指标相关联。静息时，患者的 LV SDI 显著大于对照组（p<0.001），但 IVA 无差异（p=0.22）。运动应激时，患者机械不同步的发生率（SDI>4.6%，对照组+2SD）从基线时的 25%增加到 84%。SDI（运动-静息）与运动-静息时 LV 射血分数（p<0.001）和每搏量（p=0.006）的差异相关。与对照组相比，患者的 LV 射血分数、心输出量和 IVA 在运动时的增加显著减少（交互作用，均 p<0.05），反映在 IVA-心率斜率较平缓，收缩储备受损（p=0.018）。患者的心脏 T2与基线时的 LV SDI（r=-0.44，p=0.011）和 IVA-心率斜率（r=0.36，p=0.044）相关。
静息时 LV 不同步与心肌铁负荷相关。运动应激进一步揭示了重型β地中海贫血患者的左心室运动不同步和收缩储备受损。
