Aneurysms of the pulmonary artery.

P ulmonary artery (PA) aneurysms (PAAs) are rare and infrequently diagnosed. Deterling and Clagett 1 discovered 8 cases of PAAs in 109 571 consecutive postmortem examinations. PAAs generally occurred in a younger age group than aortic aneurysms with an equal sex incidence. 2 Eighty-nine percent of all PAAs were located in the main PA, whereas only 11% were located in the pulmonary branches. 3 When affecting the PA branches, PAAs in the left PA were more common than in the right PA. An aneurysm is defined as a focal dilatation of a blood vessel involving all 3 layers of the vessel wall. Pseudoaneurysms, on the other hand, do not involve all layers of the arterial wall but possess a higher risk of rupture. In computed tomography, the upper limit for adults of the main PA diameter is 29 mm, and the upper limit of the interlobar PA is 17 mm. 4 Therefore, Nguyen et al 5 describe a PAA as a focal dilatation of the PA beyond its maximal normal caliber. In contrast, Brown and Plotnick 6 define a PAA as a PA with a diameter exceeding 40 mm, distinguishing between an ectasia of the PA and a true PAA. However, both definitions do not relate the PAA threshold to body dimensions or to the diameters of other vessels. In our center, the upper limit of the main PA diameter (29 mm) was defined as a PAA. In case of a PAA in children, the PAA size was compared with the normal values according to the method of Kampmann et al. 7 In high-risk patients, the diameter of the PAA was indexed to the body weight according to patients presenting with an aneurysm of the aorta. Origin Various origins of PAA have been described, allowing us to differentiate among congenital causes, acquired causes, and idiopathic PAA (Table 1). Congenital causes have been recognized as the major reason for PAA formation. More than 50% of all cases were associated with congenital heart disease. In general, it is presumed that increased flow caused by left-to-right shunt results in increased hemodynamic shear stress on the vessel walls and therefore promotes aneurysm formation in the PAs. 5 The 3 most frequent congenital heart defects associated with a PAA are, in decreasing order, persistent ductus arteriosus, ventricular septal defects, and atrial septal defects. The aortic valve has also been identified as a major congenital cause …