Prognostic Significance of Small Pulmonary Vessel Alteration Measured by Chest Computed Tomography in Connective Tissue Diseases With Pulmonary Arterial Hypertension

Background: Pulmonary arterial hypertension (PAH) is characterized by structural alterations of pulmonary vessels. Few studies have explored the clinical significance of quantitative assessment of pulmonary small vessels by chest computed tomography (CT). Our aim was to assess whether the prognosis of connective tissue diseases (CTD)-PAH patients could be assessed through pulmonary small vessels measured by chest CT. Methods: In all, 42 CTD-PAH patients diagnosed based on right heart catheterization were retrospectively investigated. All patients underwent a chest CT within 1 month before and after right heart catheterization examination. Main pulmonary artery (MPA) and the cross-sectional area of small pulmonary vessels <5 mm(2) as a percentage of total lung area (%CSA (<5)) were measured. The primary endpoint was a composite clinical worsening endpoint. Results: After a median follow-up time of 30.5 (interquartile range, 8.5 to 45.25) months, endpoint events occurred in 16 (38.1%) patients after 19.5 (interquartile range, 10.0 to 45.5) months. Cox univariate proportional hazard analysis showed that pulmonary vascular resistance, MPA diameter, and %CSA (<5) were associated with the end point. A combination of MPA diameter and %CSA (< 5) was the independent risk factor for the prognosis (hazard ratio, 2.180 [95% confidence interval, 1.405-3.383], P=0.001). Kaplan-Meier analysis showed that CTD-PAH patients satisfying %CSA (< 5) of 36.75 mm had the highest risk of experiencing the endpoint. Conclusion: Among the pulmonary vascular indicators measured by chest CT, in addition to MPA, %CSA (< 5) may be a potential independent risk factor for poor long-term prognosis in Chinese CTD-PAH patients.