Relevance of width of right descending branch of pulmonary artery as a radiological sign of pulmonary hypertension.

An enlargement of the diameter of the right descending branch (RDB) of the pulmonary artery in chest radiographs may serve as a sign of pulmonary arterial hypertension. We tried at first to establish exactly the normal values for men and women of different age, analysing the radiographs of 112 healthy subjects. There is a relationship of RDB diameter to sex and age. We compared the RDB diameters in 95 men suffering from chronic bronchitis with the pulmonary arterial pressure, flow, and resistance, and with the right ventricular work: a highly significant relationship of RDB diameter to all but the blood flow values was found. Considering (in men over 40 years of age) a diameter of the RDB of 18 mm. or more as pathological, the reliability of the diagnosis of pulmonary hypertension in chronic bronchitis was 72·2% with readable films, or 64·2% when not reliably readable chest films were included. Nevertheless, a similar comparison in patients with mitral stenosis indicates that the radiographic picture of pulmonary hypertension differs according to the initial disease. Here we discuss the factors which may influence the RDB diameter.