Pulmonary hypertension (PH) is a leading cause of death in patients with systemic sclerosis (SSc; scleroderma). Although right-sided heart catheterization (RHC) is the gold standard for diagnosing PH, it is an invasive test with associated risks. The submaximal heart and pulmonary evaluation (step test) is a noninvasive, submaximal stress test that could be used to identify patients with PH. The purpose of this study is to assess the correlation between change in end tidal carbon dioxide (ΔPETCO2 ) from rest to end-exercise on the step test and mean pulmonary artery pressure (mPAP) on RHC in SSc patients.
This is a retrospective cohort study of patients with limited or diffuse cutaneous SSc who were evaluated in an academic cardiology practice between November 2007 and November 2011 and underwent a step test and RHC. Statistical analysis was performed using Spearman's correlation test and multivariable linear regression.
A total of 679 charts were reviewed. Nineteen SSc patients who underwent a step test and RHC were included. ΔPETCO2 was negatively correlated with mPAP (r = -0.82, P < 0.0001). In a multivariable linear regression model evaluating the relationship between ΔPETCO2 and mPAP, controlling for age, sex, and time between and order of step test and RHC, ΔPETCO2 remained the only variable statistically significantly associated with mPAP (P < 0.001). The step test had a sensitivity of 100%, specificity of 75%, positive predictive value of 93.8%, and negative predictive value of 100% for the diagnosis of PH.
ΔPETCO2 on the step test has a strong, statistically significant negative correlation with mPAP on RHC.