Division of Pediatric Pulmonology, Children's Hospital Los Angeles, USC Keck School of Medicine, Los Angeles, California, USA.
Am J Hematol. 2013 Mar;88(3):193-7. doi: 10.1002/ajh.23370. Epub 2013 Jan 22.
Exercise performance is decreased in patients with Thalassemia major (TM), but the relative impact of anemia and iron overload on exercise capacity is unknown. We assessed the cardiopulmonary function of 71, well-transfused TM patients via graded treadmill exercise stress test. All patients underwent MRI of the heart, pancreas, and liver and diagnostic phlebotomy. Patients ranged in age from 13 to 46 years of age. Fifteen patients were excluded from analysis due to submaximal effort. Mean Vo2 max was 83.0% of predicted and was limited by abnormal cardiovascular mechanisms, consisting of a decreased O2 pulse (86.6% of predicted) in men and decreased maximum heart rate (HR) response (85% of predicted) in women. Patients with hemoglobin less than 12 g/dL had lower O2 pulse and Vo2 max, regardless of sex. Cardiac iron was negatively associated with maximum HR response and Vo2 max (r2 = 0.10 and 0.08, respectively, P < 0.05). Vo2 max was correlated with cardiac R2*, hs-CRP, sex and hemoglobin in decreasing strength of association. In thalassemia, exercise performance is limited by impaired stroke-volume reserve in men and blunted HR response in women. Iron toxicity may be mediated through vascular inflammation and direct modulation of HR response to exercise.
重型地中海贫血（TM）患者的运动表现下降，但贫血和铁过载对运动能力的相对影响尚不清楚。我们通过分级跑步机运动应激试验评估了 71 名输血良好的 TM 患者的心肺功能。所有患者均接受了心脏、胰腺和肝脏的 MRI 检查和诊断性放血。患者年龄在 13 岁至 46 岁之间。由于努力不足，有 15 名患者被排除在分析之外。平均 Vo2 max 为预测值的 83.0%，并受到异常心血管机制的限制，包括男性的 O2 脉冲降低（预测值的 86.6%）和女性的最大心率（HR）反应降低（预测值的 85%）。血红蛋白低于 12 g/dL 的患者无论性别如何，其 O2 脉冲和 Vo2 max 均较低。心脏铁与最大 HR 反应和 Vo2 max 呈负相关（r2 分别为 0.10 和 0.08，均 P<0.05）。Vo2 max 与心脏 R2*、hs-CRP、性别和血红蛋白呈负相关，其相关性逐渐减弱。在地中海贫血中，运动表现受限的原因是男性的每搏量储备受损，女性的 HR 反应减弱。铁毒性可能通过血管炎症和对运动时 HR 反应的直接调节来介导。
