A radiologic index of pulmonary arterial hypertension.

A new radiologic index indicative of pulmonary artery hypertension is presented. It was obtained by measuring the horizontal distances from the midline to the first divisions of the right and left pulmonary arteris, and dividing the sum of these distances by the maximum transverse diameter of the thorax. The index was significantly different in groups with and without pulmonary hypertension and was abnormal (above 38 percent in 111 of 150 patients with cardiovascular disease and pulmonary arterial hypertension (PAH). None of the cases with increased pulmonary flow from cardiac shunts but normal PAP had an anbormal index. Thus, an abnormal index suggested PAH but correlated poorly with the extent of hypertension.