Predictors of functional capacity in patients with pulmonary hypertension

Abstract

Introduction: The 6-minute walk test (6 MWT) distance is frequently used in the prediction of pulmonary hypertension (PH) prognosis. However, potential surrogates of this measure have not been established. We aim to describe the clinical, echocardiographic, and laboratorial criteria determining the 6 MWT distance in patients with PH. Methods: In 22 consecutive PH patients, functional capacity was evaluated by the 6 MWT distance and compared with levels of neurohormonal activation biomarkers and echocardiographic parameters for right ventricular (RV) function. Results: A correlation between the 6 MWT distance and several clinical parameters was found: Borg’s pre-test classification (R=-0.46; p=0.038); WHO functional class (p=0.029). Patients with higher levels of aldosterone (R=-0.46; p=0.030), renin (R=-0.43; p=0.046) and mid-regional pro-adrenomedullin (MR-proADM, R=-0.53; p=0.009) had worse 6 MWT performance. The opposite was true for natremia levels (R=0.55; p=0.006). There was a positive correlation between the 6 MWT distance and RV global longitudinal peak systolic strain rate and early diastolic strain rate (R=0.49; p=0.038 and R=-0.55; p=0.018, respectively). On multivariate analysis, only natremia and early diastolic strain rate were predictors of the 6 MWT distance. Conclusion: The 6 MWT distance correlated with renin-angiotensin-aldosterone system activation and parameters for RV myocardial deformation. The new biomarker MR-proADM proved to be useful in the prediction of the functional capacity.