The role of the pulmonary artery–ascending aorta ratio as a non-invasive indicator of pulmonary hypertension in interstitial lung disease

English:

Pulmonary hypertension (PH) represents a severe complication that significantly worsens the prognosis of patients with interstitial lung disease (ILD). While early identification of PH throughout the clinical course of ILD is paramount, referrals for the gold-standard right heart catheterization remain constrained, limited not only by availability or clinical suspicion but primarily by stringent indications. Historically, most patients with Group 3 PH did not benefit from treatment, as there were only very limited therapeutic options available in recent years. However, emerging pharmacological advancements have begun to expand the treatment landscape for PH-ILD, making early non-invasive screening more clinically pertinent than ever. This literature review evaluates the diagnostic utility and predictive significance of the non-invasively measured pulmonary artery-to-ascending aorta diameter ratio (PA:A ratio) via computed tomography as a robust screening tool for suspected PH-ILD. Contemporary evidence indicates that a PA:A ratio threshold of ≥0.9 serves as an optimal predictor for elevated (mean pulmonary artery pressure >20 mmHg) in patients with idiopathic pulmonary fibrosis, demonstrating a specificity of 83%. Furthermore, a ratio of ≥1.0 is established as an independent predictor of significant survival decline and increased mortality rates. Ultimately, the PA:A ratio is a pragmatic, reproducible, and highly accessible non-invasive marker that plays a pivotal role in early risk stratification, helping clinicians identify high-risk cohorts who may benefit from comprehensive diagnostic workups and emerging specialized therapeutic strategies.