Six-Minute Walk Test in Sarcoidosis Patients with Cardiac Involvement

Introduction: Cardiac involvement in sarcoidosis is of critical importance, due to the poor prognosis if this organ manifesta- tion is left undiagnosed and untreated. The six-minute walk test (6 MWT) is a useful test to evaluate exercise tolerance of sarcoid patients. We aimed to assess the 6 MWT value in diagnosis, course and treatment monitoring of patients with cardiac sarcoidosis. Materials and methods: 47 patients were included: 22 with pulmonary sarcoidosis and cardiac involvement (13 women, 9 men), 25 with pulmonary sarcoidosis, with no changes in the heart (15 women, 10 men), and 18 healthy volunteers as controls (12 women, 6 men). Out of 22 patients with cardiac involvement 11 were treated for heart sarcoidosis with prednisone (9 pts—initial dose 60 mg daily and 2 pts—40 mg daily). 11 pts in this group were not treated. In all patients sarcoidosis was confirmed histopatologically. Magnetic resonance imaging was used to diagnose involvement of the heart. In the studied groups we assessed: heart rate (HR), oxygen saturation, distance in 6 MWT and Borg dyspnea score. Results: Patients with cardiac sarcoidosis desaturated more during exercise (DSaO_2max = 3.5 ± 3.2 vs. 0.38 ± 0.69; p = 0.004) and had a lower increase of HR in first minute during the 6 MWT (DHR₁ = 21.81 ± 11.72 vs. 50.61 ± 12.35; p = 0.0001) when compared to healthy subjects. Significantly lower increase of HR in first minute of 6 MWT was observed in patients with cardiac sarcoidosis when compared to patients with pulmonary sarcoidosis with no cardiac involvement (DHR₁ = 21.81 ± 11.72 vs. 38.8 ± 18.17, p = 0.01). After introduction of treatment in sarcoidosis group, significantly higher (p = 0.02) increase of HR in first minute of 6 MWT as compared to baseline test was observed. Conclusions: The six-minute walk test is useful in diagnosing cardiac involvement in sarcoidosis. The increase in HR during exercise and decrease degree of desaturation were a good predictors of the response to therapy.