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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., (Copyright © 2012 Wiley Periodicals, Inc.)

Iron endocrinopathy and cardiomyopathy are common in chronically transfused thalassaemia major patients, but relatively rare in chronically transfused patients with sickle cell disease. Since magnetic resonance imaging can demonstrate preclinical organ iron deposition, we hypothesized that pancreas and cardiac R2* would likewise be lower in sickle cell disease patients than thalassaemia major patients having comparable transfusional burdens. To test this hypothesis, we examined pancreatic and cardiac iron in a convenience sample of 100 chronically-transfused sickle cell disease and 131 thalassaemia major patients. Cardiac R2* (30 ± 9·2 vs. 73 ± 53 Hz, P < 0·0001) and pancreatic R2* (52 ± 62 vs. 253 ± 224 Hz, P < 0·0001) were significantly lower in sickle cell disease than thalassaemia major. Liver iron concentration was similar in both groups (14·9 ± 9·8 vs. 12·3 ± 8·4 mg/g dry weight, P = 0·101). The observed disparity in pancreatic and cardiac iron loading between sickle cell disease and thalassaemia major patients mirrors prior observations of organ toxicity in these patients. Greater cumulative transfusional iron exposure in thalassaemia major patients partially explains these observations but our data also suggest innate differences in labile iron handling between the two diseases. [ABSTRACT FROM AUTHOR]