Pulmonary Artery Diameter and Pulmonary Hypertension

Diagnostic Thresholds

The American College of Radiology establishes that a main pulmonary artery ≥3.0 cm should be reported as dilated, with a measurement of 3.4 cm exceeding this threshold, indicating a high likelihood of pulmonary hypertension 1, 2, 3
A diameter >3.32 cm has been associated with pulmonary arterial hypertension, although the exact sensitivity and specificity may vary 1, 2, 3
The 90th percentile cutoff values from the Framingham Heart Study (3,171 individuals) are 29 mm in men and 27 mm in women, providing a reference point for pulmonary artery diameter 1, 2, 3

A main pulmonary artery diameter >29 mm demonstrates 87% sensitivity and 89% specificity with a 97% positive predictive value for pulmonary hypertension, as per the American College of Radiology 4, 5
Thresholds of >29.5 mm and >31.5 mm show sensitivities of 71% and 52% with specificities of 79% and 90% respectively, highlighting the importance of accurate measurement 1, 2, 3
A measurement of 34 mm substantially exceeds all validated thresholds for pulmonary hypertension, indicating a high likelihood of disease 1, 4, 5

The pulmonary artery to ascending aorta ratio (PA:A) is a useful indicator of pulmonary hypertension, with a ratio >1.0 having a 96% positive predictive value for disease 1, 2, 4, 5
A segmental artery to bronchus ratio >1:1 suggests elevated pulmonary vascular pressures, which may be indicative of pulmonary hypertension 4, 5, 6
Right ventricular enlargement and interventricular septal flattening indicate RV pressure overload, which may be associated with pulmonary hypertension 4, 5, 6

Echocardiography is recommended to estimate pulmonary artery systolic pressure, assess RV function, and evaluate for structural heart disease, as per the American College of Radiology 4, 5
Right heart catheterization remains necessary to confirm pulmonary hypertension before initiating specific therapy, according to the American College of Radiology 4, 5
Screening for underlying etiologies such as HIV, sickle cell disease, systemic sclerosis, connective tissue diseases, chronic thromboembolic disease, and left heart disease is essential for accurate diagnosis 1, 2, 3

Pulmonary hypertension is relatively rare, with 15-50 cases per million, but idiopathic pulmonary arterial hypertension represents at least 40% of cases and is typically diagnosed when advanced, highlighting the importance of early detection 1, 2, 3
Recognition and reporting of pulmonary artery dilation by radiologists is critical for early detection and diagnosis of pulmonary hypertension, as emphasized by the American College of Radiology 1, 2, 3