Six-minute walking distance is a robust predictor of mortality in stable chronic obstructive pulmonary disease...

Most patients with COPD are examined with specific pulmonary function tests and blood samples in addition to six-minute walking distance (6MWD), while few are examined by echocardiography and even fewer by invasive right heart catheterization (RHC). However, the relative prognostic value of these indices of disease remains to be defined.

We aimed in the present study to identify predictors of mortality in a cohort of COPD patients who had undergone comprehensive testing of pulmonary function, echocardiography and RHC.

The study included 97 outpatients with stable COPD in GOLD stages I-IV, after excluding three patients receiving a lung transplant. All patients underwent preinclusion screening where patients with left ventricular disease and other major comorbidities were excluded. Spirometry, blood tests, 6MWD and echocardiography of right and left heart were carried out, and RHC was performed at rest.

During a mean follow-up of 7.6 ± 0.6 years, 44 patients died. Pulmonary hypertension was diagnosed in 32 patients (33 %) and was associated with mortality (p = 0.029). 6MWD, right ventricular tricuspid annular plane systolic excursion and myocardial performance index, mean pulmonary artery pressure, pulmonary vascular resistance, arterial oxygen tension, forced expiratory volume in one second, and oxygen uptake were all associated with mortality. However, 6MWD was the only significant variable in the multivariable Cox regression model (p = 0.001).

6MWD was the most robust prognostic determinant of mortality in a stable COPD population free of major comorbidities.