Patients with this disease often have systemic pressures of the right ventricle secondary to obstruction in the lobar, segmental, and subsegmental branches. Small segmental artery stenting, particularly in patients with congenital pulmonary stenosis, has been less successful.
Peripheral pulmonary artery stenosis is well described in children 3-5 but not in the adult population, where it is often underrecognized. Esta was recently included in the latest classification of PH (Nice, 2013) as part of group 5 (PH with unclear multifactorial mechanism), under the name “segmental PH.” PPAS is a rare disease that is commonly misdiagnosed as idiopathic. PPAS can present as an isolated congenital problem or, more commonly, as part surgery for congenital heart disease involving pulmonary artery reconstruction.
In addition, Takayasu arteritis and Behcet disease have been associated with pulmonary artery stenoses that required immunosuppressive therapy and pulmonary artery balloon angioplasty with or without stenting. Isolated cases of PPAS in adulthood have been seldom reported, a fact that can reflect a low prevalence of the disease in addition to underrecognition and misdiagnosis. These last two factors are of great relevance, since patients may not receive appropriate treatment (i.e., balloon or stent angioplasty) or the therapy might be inappropriate for PPAS (specific therapies or pulmonary thromboendarterectomy (3)
Treatment for PPAS includes surveillance, for those asymptomatic patients with preserved RV function and symmetric pulmonary blood flow, and balloon angioplasty, cutting balloon angioplasty, stent implantation, or surgery, for those with symptoms of right heart failure, substantial elevation of RV pressures, marked asymmetry in pulmonary blood flow (<25% of the total flow to a single lung), severe pulmonary regurgitation, or worsening hemodynamics or RV function. Recurrent stenosis is not uncommon, as it occurs in approximately 35% of successfully dilated vessels. Stent placement in the central pulmonary arteries has been performed with success, but stenting of small segmental arteries, particularly in patients with congenital PPAS, has been less successful. In recent years, surgical intervention for PPAS has been associated with low mortality and a reduction of the RV/aortic pressure ratio in half, a hemodynamic improvement that has been maintained during follow-up.However, surgery is limited to proximal pulmonary artery lesions; distal branches are difficult for the surgeon to repair. (4)
Patients selected for balloon angioplasty are those with discrete central or multiple segmental lesions of stenosis with significant elevation of right ventricular pressures, marked inequality of blood flow and symptoms. In patients destined for univentricular circulation, pulmonary artery distortions in symptomatic patients and in those with cavopulmonary shunts are additional indications for pulmonary artery balloon angioplasty.
The vascular response to balloon dilation is complex and involves several factors including vascular endothelial growth factor, basic fibroblast growth factor, and nitric oxide. The balance between reendothelialization and smooth muscle proliferation may determine neointimal hyperplasia which leads to restenosis. Restenosis has been described after balloon dilation but little is known about its frequency, nature of occurrence, and time course.
Indications for stent therapy in the pulmonary artery tree are in those lesions not responsive to conventional balloon dilation. These are stenoses due to: kinking or tension (following the LeCompte maneuver or systemic to pulmonary artery shunts), external compression (from the neoaortic reconstruction following Norwood stage I), intimal flaps, stenoses presenting in the early postoperative period, relatively mild stenosis and restenosis following successful balloon angioplasty. Compliant (dilatable but elastic) stenotic lesions are also unlikely to respond to balloon angioplasty and would also benefit from stent therapy.
Surgical repair of peripheral pulmonary arterial lesions, in general, has been disappointing with a 50 to 60% restenosis rate at 5 years. Certain lesions however, such as supravalvular pulmonary stenosis or bifurcation stenosis of the branch pulmonary arteries are best managed by surgical repair. (5)