Peak steps to measure ''capacity for activity'': Actigraphy in the ADAPT registry with oral treprostinil.

Pulmonary arterial hypertension (PAH) patients have low activity time. Actigraphy provides an objective quantification of movement outside of clinic visits (home, work, social activities). Summary actigraphy measures (total daily steps or activity time) have not been shown to increase after adding therapies in patients with PAH. We developed a novel treatment responsive metric, Peak Steps, to measure the 'capacity for movement' in patients with PAH. Using data from the ADAPT registry (NCT03045029), we calculated Peak Steps and used summary actigraphy measurements and correlated it with six-minute walk distance (6MWD) and emPHasis-10 quality of life scores. After exposure to oral treprostinil, we observed a significant increase in Peak Steps, but no change in total daily steps or activity time. Peak Steps correlated strongly with 6MWD and emPHasis-10 scores. We propose that Peak Steps is a more sensitive marker of treatment response than traditional actigraphy parameters, which can have large behavioral influences.