Predicting Survival in IPF With CT-Measured Pulmonary Artery: Aorta Ratio

Pulmonary artery to aorta (PA:A) ratio measurement is an effective method for predicting elevated mean pulmonary artery pressure (mPAP) and survival in patients with idiopathic pulmonary fibrosis (IPF). Patients with a PA:A >0.9 had a worse prognosis, according to findings published in Respirology.¹

Mitsuaki Yagi, MD, from Tosei General Hospital and Nagoya University Graduate School of Medicine in Japan, and colleagues sought to examine the prognostic value of PA:A measurements and predict the relationship between elevated mPAP and survival in patients with IPF without further invasive testing.

In an observational study, pulmonologists used computed tomography to measure the diameters of the pulmonary artery and descending aorta in 177 patients with IPF (83.6% men; mean age: 65.4±7.8 years). To measure mPAP, the patients underwent right heart catheterization. 

Patients with IPF were excluded from the study if they had long-term oxygen therapy, if right heart catheterization was not performed at the initial visit, and if pulmonary artery wedge pressure was higher than 15 mm Hg.

Patients with PA:A >0.9 had a predicted mPAP of >20 mm Hg (area under the curve, 0.75; 95% CI, 0.65-0.84; P <.001). The researchers also found that the PA:A ratio, 6-minute walk test, and diffusion capacity for carbon monoxide were independent explanatory variables that correlated significantly with mPAP (P <.0001, P =.009, and P =.002, respectively).

Other findings corroborated previous studies^2-7: patients with borderline pulmonary hypertension (PH) and mPAP >20 mm Hg had a worse prognosis than patients who did not have PH and had mPAP ≤20 mm Hg.

The study investigators noted that the current study provided an optimal cut-off value at an early stage of IPF: “[W]e demonstrated that a PA:A >0.9 was the optimal cut-off value for predicting mPAP > 20 mm Hg and that patients with a PA:A > 0.9 had a worse prognosis than those with a PA:A ≤ 0.9.”

“Measurement of the PA:A may be a useful and convenient method to predict elevated mPAP and survival in mild-to-moderate IPF,” they concluded.

Study Limitations

• The single-site study in Japan is not representative of patients worldwide.
• Only 5.1% of patients had PH, which may have led to the insignificant difference in survival rates between the patients with normal mPAP and the group with PH.

Because the study was cross-sectional, researchers were unable to determine the changes in disease progression.