Dynamic three-dimensional anatomy of pulmonary arteries in pigs with aorto-to-pulmonary artery shunts

Accurate quantitation of three-dimensional pulmonary arterial geometry is difficult in vivo by the usual clinical imaging techniques. We have used a fast, multislice, computed tomography (CT) scanner, the dynamic spatial reconstructor (DSR), to obtain such measurements. After one injection of contrast medium into the right atrium, all major pulmonary arteries were imaged in three dimensions at 60 per second intervals throughout several cardiac cycles. Computer-generated pseudothree-dimensional displays were generated to show the arteries from several views so that superposition of arteries could be avoided. Using this technique, we have quantitated pulmonary arterial geometry in five pigs, three of them with surgically created aortopulmonary shunt and two with sham shunts. Pulmonary arterial cross-sectional areas (CSA) along the length of the left and right pulmonary arteries as they course through the lower lobes of the lungs were measured at peak-systole and end-diastole. From these image data, the systolic to diastolic change in CSA was measured. The regression line relating the CSA at these two phases had slopes in the five pigs ranging from 0.41 to 0.85. The magnitude of this slope corresponded closely with pulmonary arterial pressure, which ranged from 20 to 92 mm Hg.