The 6-min walk test: an independent correlate of elevated tricuspid regurgitant jet velocity in children and young adult sickle cell patients

Abstract

Elevation of echocardiography-determined tricuspid regurgitant jet velocity (TRV) predicts high systolic pulmonary artery pressure. The present study tested the hypotheses that elevated tricuspid regurgitant jet velocity is associated with both hemolysis and hypoxia and abnormal 6-min walk test (6MWT) results. This study aims to correlate elevated TRV with different clinical laboratory findings and 6MWT and to find the independent predictors of increased TRV. A prospective study of 80 patients aged 5-25years old with sickle cell disease (SCD) under basal conditions and 40 matched controls was conducted. Hemolytic analysis was assessed by the levels of lactate dehydrogenase, serum bilirubin, and reticulocyte count. Oxygen saturation determination using pulse oximeter and 6MWT were done. The overall prevalence of elevated TRV (≥2.5m/s) was 28.75%. Associated risk factors were older age (r = 0.28, p = 0.01), longer duration of disease (r = 0.25, p = 0.025), higher reticulocytic count (r = 0.344, p = 0.002), lower O2 saturation (r = -0.574, p = 0.0001), and shorter walked distance in 6MWT (r = -0.75, p = 0.0001). By multivariate logistic analysis, only the distance walked during 6MWT was the independent correlate of elevated TRV (odds ratio = 0.85; 95% CI = 0.74 to 0.98 p = 0.033). The study provides evidence for independent association of TRV with abnormal 6MWT results. The 6-min walk test can be used as noninvasive adjuvant tool for functional capacity assessment of SCD patients with elevated TRV.