Right Ventricular to Left Ventricular Ratio at CT Pulmonary Angiogram Predicts Mortality in Interstitial Lung Disease

Patients with interstitial lung disease (ILD) may develop pulmonary hypertension (PH), often disproportionate to the severity of the ILD. The right ventricular to left ventricular diameter (RV:LV) ratio measured at CT pulmonary angiogram (CTPA) has been shown to provide valuable information in patients with pulmonary arterial hypertension and to predict death or deterioration in acute pulmonary embolism.

Demographic characteristics, ILD subtype, echocardiography, and detailed CTPA measurements were collected in consecutive patients undergoing both CTPA and right heart catheterization at the Royal Brompton Hospital between 2005 and 2015. Fibrosis severity was formally scored according to CT criteria. The RV:LV ratio at CTPA was evaluated by using three different methods. Cox proportional hazards analysis was used to assess the relation of CTPA-derived parameters to predict death or lung transplantation.

A total of 92 patients were included (64% male; mean age 65 ± 11 years) with an FVC 57 ± 20% predicted, corrected transfer factor of the lung for carbon monoxide 22 ± 8% predicted, and corrected transfer coefficient of the lung for carbon monoxide 51 ± 17% predicted. PH was confirmed at right heart catheterization in 78%. Of all the CTPA-derived measures, an RV:LV ratio ≥ 1.0 strongly predicted mortality or transplantation at univariate analysis (hazard ratio, 3.26; 95% CI, 1.49-7.13; P = .003), whereas invasive hemodynamic data did not. The RV:LV ratio remained an independent predictor at multivariate analysis (hazard ratio, 3.19; 95% CI, 1.44-7.10; P = .004), adjusting for an ILD diagnosis of idiopathic pulmonary fibrosis and CT imaging-derived ILD severity.

An increased RV:LV ratio measured at CTPA provides a simple, noninvasive method of risk stratification in patients with suspected ILD-PH. This should prompt closer follow-up, more aggressive treatment, and consideration of lung transplantation.