6-minute walk test predicts pulmonary artery pressure in patients with collagen vascular disease associated interstitial pneumonia

Abstract

[Objective] It has been reported clinical importance of pulmonary hypertension(PH) in collagen vascular disease(CVD), however the role of PH in interstitial pneumonia related CVD(CVD-IP) has been scarcely evaluated. We sought to determine the prediction factor of mean pulmonary artery pressure(MPAP) in patients with CVD-IP.

[Method]Patients with CVD-IP underwent right heart catheterization(RHC) within 3 months of initial evaluation at our institution. Patients with left ventricular dysfunction, incomplete follow-up, and patients with respiratory failure were excluded.

[Results] We studied 44 patients, (19 male, mean age 59.8±11.0years). They were 13 with RA, 13 with SSc, 9 with PM/DM, and 9 with others. PaO2 at rest was 83.1±9.6mmHg,MPAP was 17.2±5.5mmHg (>20mmHg, 13(29.5%)), cardiac index(CI) was 3.6±0.8L/min/m2, pulmonary vascular resistance index(PARI) was 223±102 Wood units/m2, %vital capacity(%VC) was 78.4±21.0%, percentage of carbon monoxide diffusing capacity (%DLco) was 50.9±17.6%, and 6-min walk distance(6MWD) was 502±142 m, and minimum SpO₂ at 6-min walking test (mSpO₂) was 85.6±5.9%, respectively. The median observation period was 31.8 months with 11 patients died. In the univariable model, MPAP was significantly correlated with %DLco (r=-0.377,P=0.013), and mSpO₂ (r=-0.552, P=0.0001). In the multivariable model, MPAP was significantly correlated with 6MWD (r=-0.360,P=0.019) and mSpO₂ (r=-0.595,P<0.001).

Conclusion] 6MWD and mSpO₂ were independent predictors of MPAP in CVD-IP.