Characterization of Pulmonary Arterial Hypertension Patients Walking More Than 450 m in 6 Min at Diagnosis

BackgroundAt diagnosis of pulmonary arterial hypertension (PAH), some patients are considered to have a “near-normal” 6-min walk distance (6MWD) (ie, > 450 m). Because they are generally excluded from randomized controlled trials, little is known about these patients.MethodsWe analyzed the baseline characteristics and treatment responses of 49 consecutive patients with a 6MWD > 450 m at the time of newly diagnosed PAH. Data from this cohort were then compared with data from hemodynamically matched patients with a 6MWD ≤ 450 m.ResultsPatients with a 6MWD > 450 m were either in World Health Organization (WHO) functional class (FC) II (n = 23) or III (n = 26) at baseline. Compared with patients in FC II, those in FC III had more severe hemodynamic impairment (ie, a lower cardiac index and higher pulmonary vascular pressures and resistance) but similar 6MWD. At first evaluation after initiation of PAH-specific treatment (3–6 months), FC improved (FC I-II: n = 38; FC III: n = 11, P < .005) and cardiac index increased. However, 6MWD remained unchanged. Compared with matched patients with a 6MWD ≤ 450 m (n = 98), individuals with a 6MWD > 450 m were approximately 9 years younger (P = .0006) and had a lower BMI (P = .0009).ConclusionsAnthropometric characteristics such as younger age and lower BMI may explain higher 6MWD in some PAH patients. In the cohort of patients with a 6MWD > 450 m, hemodynamic indices and WHO FC were more sensitive than 6MWD in detecting changes secondary to PAH-specific treatments.