MECHANICAL-PROPERTIES OF THE PULMONARY-ARTERIES AFTER THE ARTERIAL SWITCH OPERATION FOR COMPLETE TRANSPOSITION

This study was designed to determine, first, the stiffness of the pulm onary arteries and, second, the relationship between the stiffness of the pulmonary arteries and the success rate of balloon angioplasty in patients with complete transposition after an arterial switch operatio n. Indexes of pulmonary arterial wall stiffness, percent change in the radius during a cardiac cycle and the pressure elastic modulus, were calculated from the pulmonary arterial pressure and radius measured fr om a cineangiogram. Of the patients, 13 had no significant stenosis, w hile 25 had significant stenoses and, therefore, underwent balloon ang ioplasty. In all, we dilated 33 stenotic lesions. In the presence or a bsence of postoperative pulmonary stenosis, the percent change in the radius of the pulmonary trunk was significantly less than the normal v alue. The pressure elastic modulus of the trunk and its branches was s ignificantly greater than normal, and increased significantly with tim e after the operation. In patients without pulmonary stenosis, the sys tolic pulmonary arterial pressure increased concomitantly with the pre ssure elastic modulus. Balloon dilation was successful at 17 locations and unsuccessful at 16 locations. The percent change in radius was si gnificantly less for the failures than for the successes. Prior to 3.5 years after the operation, the pressure elastic modulus was < 400 g/c m(2) at most locations and balloon dilation was successful in 88%. Mor e than 3.5 years after the operation, the pressure elastic modulus was > 409 g/cm(2) in 11 of 15 locations, and balloon dilation was success ful in only one location. The increased stiffness of the pulmonary art ery may result in increased pulmonary systolic pressure in patients wi thout pulmonary stenosis, and result in a low success rate for balloon angioplasty in patients with pulmonary stenosis.