Radiologic Parameters of Pulmonary Hypertension on Thorax CT May Help Risk Stratify Patients with Fibrosing Interstitial Lung Disease

Main pulmonary artery and right ventricular diameters on computed tomography (CT) scans of the thorax were predictors of pulmonary hypertension.

In patients with fibrosing interstitial lung disease (ILD), the presence of associated pulmonary hypertension has a significant impact on the appearance of thorax computed tomography (CT). In a recently presented study at the Radiological Society of North America (RSNA) 2022 Annual Meeting, researchers found that main pulmonary artery and right ventricular diameter findings were predictors of pulmonary hypertension.

“In patients with fibrosing ILD, a combination of radiologic parameters may be used to predict the presence and severity of pulmonary hypertension,” and to guide clinical decisions on right heart catheterization, lung transplant assessment and prognosis, said Lubna Siddiqi, M.D. a resident at the Department of Diagnostic Radiology at the Schulich School of Medicine & Dentistry at Western University in London, Ontario, Canada, and colleagues.

The development of pulmonary hypertension in patients with fibrosing ILD is associated with considerably shorter survival. While earlier detection is desirable, the current gold standard for diagnosis is right heart catheterization with risk stratification being based on clinical and echocardiographic findings. However, pulmonary hypertension can occur in asymptomatic patients and echocardiography may not detect mild or early pulmonary hypertension. Dr. Siddiqi and colleagues aimed to use objective values from CT imaging to predict the presence of pulmonary hypertension in patients with fibrosing ILD.

An initial 128 patients with fibrosing ILD followed at the London Health Sciences Centre in Ontario underwent right heart catheterization. Of these patients, 94 patients (average age 66.2; 66 male) with thorax CT within six months of right heart catheterization were assessed for main pulmonary artery to aorta ratio, right to left ventricular ratio, caliber of the right and left pulmonary arteries, interventricular septal thickness, and right ventricular wall thickness, presence of pulmonary thromboembolic disease and degree of mosaic attenuation.

Pulmonary hypertension was defined as a mean pulmonary arterial pressure of 25 mmHg or greater. Radiologic data were analyzed to determine the best predictors of associated pulmonary hypertension, with the results adjusted for sex, body mass index and age.

Of the patients, 38 (40 percent) underwent right heart catheterization electively and 56 (60 percent) as part of a lung transplant assessment. The average mean pulmonary arterial pressure was 25 mmHg, wedge pressure was 9 mmHg, cardiac output was 5 L/min and pulmonary vascular resistance was 3.3 Wood units. Overall, 66 patients (70 percent) had pulmonary hypertension with an average mean pulmonary arterial pressure of 38 mmHg and a pulmonary vascular resistance of 5.7 Wood units.

Main pulmonary artery and right ventricular diameters were independent and significant predictors of pulmonary vascular resistance (F ratio 6.64, 6.32; respectively). However, the correlation between main pulmonary artery and right ventricular diameters was weak and not significant. The main pulmonary artery diameter was also a significant predictor of mean pulmonary arterial pressure (F ratio 11.5).

While the authors noted the small sample size and said they “will seek validation of these data in a separate cohort of patients,” they suggested that “these parameters could be especially helpful in populations for whom right heart catheterization is not readily available or is a contraindication.”