Reduction of the Six-Minute Walk Distance in Children with Sickle Cell Disease Is Correlated with Silent Infarct: Results from a Cross-Sectional Evaluation in a Single Center in Belgium

Abstract

BackgroundThe 6-minute walk test (6MWT) is used in adults and children affected by a wide range of chronic diseases to evaluate their sub-maximal exercise capacity. It reflects the global response of various physiological systems in a situation simulating a daily life activity.MethodsWe analyzed factors affecting the 6MWT in 46 Sickle Cell Disease children. Forty-two were treated with hydroxyurea (HU). Patients with normal test (>80% of the age-standardized predicted value) were compared to patients with abnormal test (≤80%). Baseline hematological values, clinical events, cerebrovascular disease, cardio-pulmonary parameters and disease-modifying treatment were compared according to the performance of the test.ResultsAmong the 46 patients, 14 had an abnormal 6MWT. In univariate analysis, both groups were similar for biological and clinical data. Six of the 14 patients with an abnormal 6MWT had silent infarct (SI) compared to 6/32 with a normal test (P = 0.09). When excluding chronically transfused patients, 4 of the 11 patients with an abnormal 6MWT had SI compared to 1/26 (P = 0.02). Baseline pulse oximetry was normal in both groups but slightly lower in patients with abnormal 6MWT (P = 0.02). No patient presented exercise-induced desaturation. In multivariate analysis, the only factor associated with abnormal 6MWT was the presence of SI (P = 0.045).ConclusionsIn our cohort of 46 patients characterized by high exposure rate to HU and by the absence of severe cardiopulmonary disease, the sole factor independently associated with 6MWT was the presence of SI. The lower exercise capacity of children with SI may reflect some subclinical neurological impairment as they do not differ by hemoglobin level or cardiopulmonary parameters.

Pulmonary function in children and adolescents with sickle cell disease: have we paid proper attention to this problem?

“…Two tests were performed within 30 minutes, and when there were conflicting results between the tests, a third test was performed. A normal result was defined as a 6MWD > 80% of predicted for age, a moderate result was defined as a 6MWD between 60% and 80% of predicted, and a severe result was defined as a 6MWD < 60% of predicted 29 . A significant decrease in SpO 2 (desaturation) was defined as that ≥ 3% relative to baseline 30 …”

Micro- and macrovascular function in children with sickle cell anaemia and sickle cell haemoglobin C disease

“…Then the distance walked was noted and the percentage of predicted distance was calculated by Geigers' standardized formula [31] according to age, sex and height, as previously done [32]. The 6MWT was considered as normal if the performance was more than 80% of the age-standardised predicted value and abnormal otherwise [33].…”

One-Fifth of Children with Sickle Cell Anemia Show Exercise-Induced Hemoglobin Desaturation: Rate of Perceived Exertion and Role of Blood Rheology

“…In addition, the 6MWT performance inversely correlates with the severity of the disease. [12] For instance, a recent study reported an independent association between the 6MWT performance and the presence of silent infarcts in children with SCA and no severe cardiopulmonary dysfunction [13]. Anthi et al [12] previously showed the usefulness of using the 6MWT distance as an index of pulmonary hypertension and cardiopulmonary function in adults with SCA.…”