Six-minute Walk Test Still Key in Predicting Long-Term PAH Outcomes, Study Confirms

Patients with pulmonary arterial hypertension (PAH) who can walk more than 400 meters (437 yards) on a six-minute walk test have better long-term prognosis, with lower risk of PAH-related death or hospitalization, results from a Phase 3 clinical trial show.

The study, “Association between six-minute walk distance and long-term outcomes in patients with pulmonary arterial hypertension: Data from the randomized SERAPHIN trial,” was published in the journal PLOS ONE. It investigated the association between six-minute walk distance and long-term outcomes in patients with PAH.

The study was based on data collected from the Phase 3 trial SERAPHIN (NCT00660179) evaluating Opsumit (macitentan) therapy in PAH. SERAPHIN was the first prospective, long-term study to address disease progression in more than 700 patients with PAH for a median treatment period of 2.2 years.

Researchers took advantage of the data available in the SERAPHIN study to determine if patients who performed better at the six-minute walk test (6MWT) also had better clinical outcomes.

The 6MWT evaluates exercise tolerance in chronic respiratory disease and heart failure. The test measures the distance an individual is able to walk for a total of six minutes on a hard, flat surface. The goal is for the individual to walk as far as possible in six minutes.

The study analyzed the distance reached by PAH patients in the 6MWT at baseline and six months after they started treatment with Opsumit (marketed by Actelion Pharmaceuticals).

Patients were divided into two groups — those who walked more than 400 meters, and those who walked less. In these two groups, researchers analyzed the future risk of PAH-related death or hospitalization and all-cause death until the end of the treatment period.

Patients who walked a distance farther than 400 meters six months after treatment initiation had about half the risk of having future clinical events, including PAH-related death or hospitalization as well as all-cause death. Among the 298 patients who walked 400 meters or less, there were 80 events of PAH-related death or hospitalization, whereas among the 297 patients who walked more than 400 meters there were 45 events.

The same trend was observed when looking at 6MWT values at baseline. Patients who walked shorter distances at the beginning of the trial, also were at higher risk of poorer outcomes.

In contrast, 6MWT values at month 6 were not associated with the risk of PAH-related death or hospitalization, or the risk of all-cause death, up to the end of the study. 

“Patients with pulmonary arterial hypertension walking [more than] 400 [meters] had better long-term prognosis. Although changes in six-minute walk distance were not associated with long-term outcomes, assessing absolute six-minute walk distance values remains important in the clinical management of patients with pulmonary arterial hypertension,” the researchers concluded.

Overall, the study confirms previous observations that evaluating exercise capacity can reflect prognosis in PAH patients, which supports the use of the 6MWT  in daily clinical practice and as an important measurement in clinical trials.