Abstract
Noninvasive imaging markers may be helpful in identifying higher-risk patients with various lung diseases. Pulmonary artery to aorta ratio (PA/A ratio) on computed tomography (CT) is an indicator of pulmonary hypertension, but its relationship with other hemodynamic, imaging, and physiologic measurements, functional status, and outcomes requires further investigation. We set out to determine if the PA/A ratio is related to components of right ventricular (RV) afterload (pulmonary vascular resistance (PVR), PA compliance), lung diffusion capacity, radiographic emphysema, or honeycombing on chest CT, six-minute-walk distance, and transplant-free survival in COPD and/or interstitial lung disease (ILD). Data including PA/A ratio, hemodynamics, imaging, physiologic measurements, and survival in Redefining Pulmonary Hypertension through Pulmonary Vascular Disease Phenomics (PVDOMICS) cohort participants with COPD, ILD, or both were analyzed in regression and survival models to determine the association between PA/A ratio and various outcomes. We found that PA/A ratio analyzed as a continuous variable or dichotomized (> 0.9 vs. ≤ 0.9) was associated with higher PVR and lower PA compliance in fully adjusted models. Having either a PA/A ratio > 0.9 or a more elevated PVR was associated with worse transplant-free survival, while PA compliance was not associated with survival. PVR did not appear to mediate the relationship of PA/A ratio with survival. PA/A ratio did not correlate with six-minute walk distance or presence of emphysema or honeycombing, but was related to lower lung diffusion capacity. In conclusion, PA/A ratio on CT is related to aspects of RV afterload and to survival in COPD and ILD.