From the Guidelines
Pulmonary hypertension can be suggested on CT criteria when the main pulmonary artery diameter is greater than 29 mm or the ratio of main pulmonary artery to ascending aorta diameter is greater than 1, with a positive predictive value of 97% and 96%, respectively, as reported in the most recent study 1.
Key CT Findings for Pulmonary Hypertension
- Main pulmonary artery diameter greater than 29 mm
- Ratio of main pulmonary artery to ascending aorta diameter greater than 1
- Right ventricular enlargement with a ratio of right ventricle to left ventricle diameter exceeding 1
- Enlargement of segmental pulmonary arteries with diameters greater than their accompanying bronchi
- Other supportive findings include pruning or rapid tapering of peripheral pulmonary vessels, right atrial enlargement, interventricular septal flattening or bowing toward the left ventricle, and pericardial effusion
Additional CT Criteria
- True right and left descending PA diameters of 16 mm and 21 mm, respectively
- Ratio of segmental PA to accompanying bronchus >1:1
- Enlargement of the right ventricle, RV lumen/LV lumen 1, straightening of the interventricular septum, RV free wall thickness 6 mm, pericardial thickening or effusion
- Enlargement of the bronchial arteries to a diameter of >1.5 mm
Importance of Right Heart Catheterization
While CT findings are valuable for suggesting pulmonary hypertension, right heart catheterization remains the gold standard for definitive diagnosis, as it directly measures pulmonary arterial pressure, as noted in 1 and supported by earlier studies 1.
CT in Evaluating Etiologies of Pulmonary Hypertension
CT is particularly useful for identifying potential causes of pulmonary hypertension, such as chronic thromboembolic disease, interstitial lung disease, or congenital heart defects, and can characterize various pulmonary etiologies, including IPAH, pulmonary capillary hemangiomatosis (PCH), pulmonary veno-occlusive disease (PVOD), and many diffuse lung diseases, as discussed in 1.
From the Research
CT Criteria for Pulmonary Hypertension
- The study 2 found that computed tomography angiography can be used to diagnose and estimate the severity of pulmonary arterial hypertension.
- The main pulmonary artery diameter on CT angiography has a good predictive value regarding the severity of pulmonary hypertension, with a mean diameter of 3.55 +/- 0.66 cm in patients with pulmonary hypertension 2.
- The pulmonary artery/ascending aorta ratio was also found to be significantly different in patients with pulmonary hypertension, with a mean ratio of 1.2 +/- 0.29 2.
- Other CT criteria that may be useful in diagnosing pulmonary hypertension include:
- These CT criteria can be used in conjunction with other diagnostic tests, such as right heart catheterization and echocardiography, to diagnose and estimate the severity of pulmonary hypertension 2.