Exercise capacity in patients with beta-thalassemia major: Relation to left ventricular and atrial size and function

Objectives The objective of this study was to examine the association betwe en exercise capacity and echocardiographic indexes of atrial and ventricula r function and size in patients with beta-thalassemia major. Background In patients with beta-thalassemia major, the assessment of cardi ac function with echocardiography alone does not always correspond to their functional status. Peak oxygen uptake and anaerobic threshold, on the othe r hand, constitute 2 objective and reproducible determinants of exercise ca pacity in patients with heart failure. Methods and Results Forty consecutive patients (22 women and 18 men, 18 to 30 years old) who were in stable condition while receiving regular transfus ions and 30 age and sex-matched control subjects were studied. At 2 to 3 da ys after the last transfusion, each subject underwent complete echocardiogr aphic study followed by cardiopulmonary exercise testing. Left atrial volum es (maximal [Vmax], at onset of atrial systolic [Vp], and minimal [Vmin]) a nd left ventricular volumes were measured with the biplane area-length meth od, and left atrial active emptying fraction (ACTEF) and left ventricular e jection (LVEF) fraction were calculated. Peak oxygen uptake ((V) over dot O (2)max) and anaerobic threshold (AT) were also estimated. After transfusion , patients with beta-thalassemia major had reduced (V) over dot O(2)max and AT and greater left atrial volume in comparison with control subjects. Als o, ACTEF and LVEF were significantly lower in the patient group. Moreover, (V) over dot O(2)max and AT were inversely related to Vmax (r = -0.74 and r = -0.80, respectively) and directly related to ACTEF (r = 0.85 and r = 0.8 2, respectively) in beta-thalassemia major, whereas they were poorly relate d to LVEF (r = 0.50 and r = 0.53, respectively). In the control group, (V) over dot O(2)max and AT parameters were related to Vmax and ACTEF in a simi lar way to that in the beta-thalassemia group. Conclusions in patients with beta-thalassemia major, exercise capacity does not correlate with left ventricular dimensions and function. On the contra ry, left atrial size and systolic dysfunction ore probably predictors of de creased exercise capacity.