Cardiopulmonary testing in adult patients with β-thalassemia major in comparison to healthy subjects

Abstract

β-Thalassemia patients often have a reduced capacity of exercise and abnormal respiratory function parameters, but the reasons are unclear. In order to identify the causes of the exercise limitation, we performed a cardiopulmonary exercise testing (CPET) in a group of 54 adult β-thalassemia major (TM) patients without pulmonary arterial hypertension and in a group of healthy control subjects. All subjects underwent cardiac echocardiography and carried out pulmonary function tests. TM patients also filled an IPAQ questionnaire on usual physical activity (PA).Overall, TM patients have a diminished exercise performance in comparison to control subjects. In fact, peak oxygen uptake (V'O₂ peak), expressing maximum exercise capacity, was decreased in 81.5% of the patients; similarly, anaerobic threshold (V'O₂@AT) and O₂ pulse also resulted lowered. In multivariable regression models adjusted for gender, age, BMI, and mean haemoglobin, V'O₂ peak and O₂ pulse were positively associated with cardiac iron overload (T2*). No ventilatory limitation to exercise was observed. The most important causes of exercise limitation in these patients were muscular deconditioning and reduced cardiac inotropism due to iron deposition. Only 15/54 (27.8%) TM patients used to perform vigorous physical activity. These results suggest that a program of regular physical activity may be useful to increase the tolerance to effort and therefore to improve the quality of life in these patients.

Keywords: Cardiopulmonary test; Exercise capacity; Iron overload; Muscular deconditioning; β-Thalassemia.

Fig. 1

Relationship between V’O₂ peak and cardiac T2*

Fig. 2

Relationship between O₂ pulse and cardiac T2*