Etiology of pulmonary artery dilatation and hilar dance in atrial septal defect.

Atrial septal defect is associated with increased diameter and pulsation of the pulmonary arteries. The high pulmonary flow rate produces turbulence and a murmur. Intraluminal pressure is normal and vessel wall elastic properties may be altered as in poststenotic dilatation. Pulmonary artery angiograms in 6 normal patients, 9 with pulmonary stenosis and 10 with atrial septal defect were recorded on film, projected and traced. Arterial diameters at maximum systole and diastole were measured and, with intraluminal pressures, 2 points on the elastic diagram were calculated. These points lay on the initial linear portion of the graph so that a line through them to zero wall tension gave the resting radius (Ro)Each radius value (R) was normalized by dividing by the corresponding Ro. By plotting wall tension versus strain (R/Ro), a regression line was obtained for normals significantly different from that for poststenotic dilatation (P<0.01) and atrial septal defect (P<0.01). The slope of each line approximated vessel elastance at normal pressures: normals, 2.15 X 10 dyne/cm; poststenotic dilatation, 1.00 X 10 dyne/cm; and atrial septal defect, 0.89 X 10 dyne/ cm. Increased pulmonary artery distensibility extends more peripherally in atrial septal defect, thus producing "hilar dance." A case of Marfan's syndrome showed similar changes.