Pulmonary Artery Stenosis
M. Abigail Simmons, MD
Jeremy D. Asnes, MD
Key Points
Pulmonary artery stenosis may be due to congenital or acquired disease.
Pulmonary artery stenosis should be considered as part of the differential diagnosis for any adult undergoing evaluation of pulmonary hypertension.
Indications to intervene on pulmonary artery stenosis include: 1) right ventricular systolic pressure greater than 2/3 systemic pressure, 2) Significant stenosis in the setting of right ventricular dysfunction, 3) pulmonary artery stenosis with a marked perfusion inequality or deficit, 4) regional pulmonary artery hypertension in unaffected lung segment, and 5) pulmonary artery narrowing/distortion in patients with cavopulmonary anastomoses.
Interventional techniques to address pulmonary artery stenosis include simple balloon angioplasty, cutting balloon angioplasty, and stent angioplasty.
I. Introduction
A. Obstructions or stenoses with the pulmonary arterial tree result from a diverse group of intrinsic and extrinsic factors.
B. Pulmonary artery stenoses may involve the main pulmonary artery, the left and right branch pulmonary arteries, and the lobar, segmental, and subsegmental branches of the more distal pulmonary arterial tree. Obstruction may be isolated to a single vessel or may occur at multiple sites and multiple levels.1 Management strategies for pulmonary artery stenosis include balloon angioplasty, cutting balloon angioplasty, and stent angioplasty. Patient-specific strategies depend on etiology, lesion characteristics, and patient characteristics.
II. Etiology of Pulmonary Artery Stenosis
A. Pulmonary artery stenosis can be broadly classified as either congenital or acquired (Table 7.1). In a study by Franch, 60% of congenital stenoses were found in conjunction with congenital heart disease while 40% were isolated. Isolated congenital stenosis is often found in association with genetic syndromes including Williams, Alagille, and Noonan syndrome (Fig. 7.1). In these settings, the stenoses tend to be diffuse, involving multiple segments at multiple levels of the pulmonary tree.
B. Pulmonary artery stenoses may be acquired as a result of congenital heart disease surgery, particularly if the surgery involves manipulation of the pulmonary arteries themselves. Patch material, suture lines, and distortion due to kinking or stretching of the pulmonary vessel may all contribute to postsurgical pulmonary artery stenosis (Figs. 7.2A-C and 7.3A).
Table 7.1. Etiologies of Pulmonary Artery Stenosis
Congenital Malformation of Pulmonary Arterial System
Congenital heart disease associated
Tetralogy of Fallot, pulmonary atresia, pulmonary valvar stenosis
Main, branch, or lobar artery stenoses
Isolated pulmonary artery stenosis
Main or branch pulmonary artery stenosis
Genetic Syndromes
Williams syndrome:
Diffuse involvement: branch, lobar, segmental pulmonary arteries
Alagille syndrome: Peripheral pulmonary artery stenosis
Postsurgical
Distal to site of pulmonary artery patch or anastomosis
Site of previous Blalock-Taussig shunt
Site of patent ductus arteriosus ligation or device implantation
Following removal of pulmonary artery band
Following arterial switch operation
Idiopathic Pulmonary Artery Stenosis
Takayasu arteritis: Main, branch, and lobar pulmonary artery stenosis
Fibrosing mediastinitis: Main and branch pulmonary artery stenosis
External Compression
Compression from tumor (ie bronchogenic carcinoma) or lymphadenopathy
Compression from infiltrative or fibrotic lung disease (ie sarcoidosis)
C. Pulmonary artery stenosis presenting de novo in the adult is a rare but important condition and is usually an acquired pathology.2,3 Etiologies include external compression from tumor or lymphadenopathy, fibrosing mediastinitis, systemic vasculitis (eg Takayasu arteritis or Behcet disease), thromboembolic disease, and sarcoidosis. (Table 7.1). These are often misdiagnosed as idiopathic pulmonary arterial hypertension or pulmonary hypertension due to chronic venous thromboembolism. In cases of late diagnosis, patients have often received inappropriate or incomplete therapeutic strategies with little clinical benefit.
III. Pathophysiology
Pulmonary artery stenosis results in varying degrees of ventilation/perfusion mismatch, pulmonary hypertension, vascular injury in unaffected segments, elevations of right heart pressure, right ventricular dysfunction, and limitations of cardiac output. In the presence of an intra-cardiac shunt (eg, patent foramen ovale, atrial septal defect, or ventricular septal defect) obstruction to pulmonary blood flow can result in cyanosis from shunting of deoxygenated blood to the systemic circulation due to increased resistance to pulmonary blood flow. Untreated, pulmonary artery stenosis can contribute to exercise limitation, diminished quality of life, and, in the case of congenital lesions and stenosis due to previous cardiac surgery, limited pulmonary vascular growth and post-operative mortality.4,5
IV. Interventional Strategies
A. First Balloon Angioplasty and Advancements Lock et al, were the first to perform balloon angioplasty of pulmonary arteries. Their seminal work with an experimental lamb model was quickly translated to the congenital cardiac catheterization laboratory.6,7
Rapid advancements in catheter, balloon, stent and guidewire technologies, as well as refinements in angioplasty techniques, broadened the scope of lesions that can be safely treated with transcatheter therapies. In the current era, simple balloon angioplasty, cutting balloon angioplasty, and stent angioplasty are the primary interventions for pulmonary arterial stenosis.
FIGURE 7.1: A and B, Anterior-posterior and lateral angiograms from a patient with Williams syndrome. There is diffuse disease with hypoplasia of the central pulmonary arteries and severe stenoses of almost all lobar and segmental branches. C, Severe discrete right pulmonary artery stenosis (white arrow) in a patient with Takayasu arteritis. D, Severe proximal pulmonary artery stenosis/hypoplasia in a patient with Alagille syndrome.
1. Significant elevation in right ventricular systolic pressures (≥2/3 systemic)
2. Significant stenosis in the setting of right ventricular dysfunction
3. Pulmonary artery stenosis with a marked perfusion inequality or deficit
4. Regional pulmonary artery hypertension in unaffected lung segments (mean distal pressure >25 mm Hg)
5. Pulmonary artery narrowing/distortion in patients with cavopulmonary anastomoses
 FIGURE 7.2: A and B, Stenosis due to folding of the proximal left pulmonary artery at the site of a surgical patch before (A) and after (B) stent placement. C and D, Severe right pulmonary artery stenosis related to surgical patch material before (C) and after (D) stent placement and transcatheter valve-in-valve pulmonary valve implant. D, Pulmonary artery angiogram in a patient with transposition of the great arteries following arterial switch operation. There are stenoses of the lobar branches related to surgical manipulation of the pulmonary vasculature (E) successfully treated with stent angioplasty (F). |
V. Goals of Therapy and Measures of Success
The goals of intervention include reduction in right ventricle pressure, improved distribution of pulmonary blood flow, preservation and improved growth of distal pulmonary vasculature, pressure reduction in unobstructed lung segments, and improvement in exercise capacity. Therapeutic success is measured by angiographic and/or clinical/physiologic improvement.10 Nuclear perfusion imaging helps assess regional pulmonary perfusion and the need for and success of an intervention.
VI. Standard Balloon Angioplasty
A. Balloon Expansion
1. In general, balloons either expand uniformly with a discrete waist at the site of highest resistance, or nonuniformly without a discrete waist.
2. The latter is often associated with stenosis due to external compression, kinking, or stretching of the vessel.
3. These vessels typically exhibit significant recoil limiting therapeutic benefit of balloon angiogplasty.
FIGURE 7.3: Balloon angioplasty of proximal left pulmonary artery stenosis related to surgical patch augmentation, before (A) and following (D) successful balloon angioplasty in a patient with tetralogy of Fallot. Note the discrete waist in the angioplasty balloon (B) that resolves with high-pressure inflation (C).
4. When a waist is present, successful angioplasty is dependent on its eradication.13
5. Angiography following successful balloon angioplasty often shows a non-obstructive intra-luminal filling defect indicative of an appropriate intimal and medial tear.
B. Types of Balloon Angioplasty Catheters A wide array of balloon angioplasty catheters is available for pulmonary artery balloon angioplasty. Balloon selection depends on both patient and target vessel characteristics with differences in guidewire size, shaft flexibility, balloon compliance, balloon and balloon shoulder length, and nominal/maximal inflation pressure impacting angioplasty catheter choice.
1. Low-pressure balloon angioplasty. Low-pressure balloon angioplasty (4-10 atm) using balloons 2-4 times larger than the target minimal lumen diameter has been successful in up to 60% of lesions.13,14
2. High-pressure balloon angioplasty. Success rates with high-pressure balloon angioplasty (10-22 atm) exceed those seen with low-pressure balloons. Furthermore, successful
high-pressure angioplasty is frequently achieved at lower balloon:minimal lumen ratios than those needed for low-pressure angioplasty.15 Thus, with high-pressure angioplasty, a more conservative approach, starting with ratios of 2-3:1, with incremental increases in the absence of success may be preferable.
3. In recent studies, up to one-third of pulmonary artery stenoses remain resistant to high-pressure balloon angioplasty.9 Resistance to angioplasty is more common in distal pulmonary arteries while proximal vessels exhibit higher rates of recoil. This is likely related to the variable mechanisms of stenosis at these sites. Restenosis rates of 10%-35% have been reported following simple balloon angioplasty.9,16
VII. Cutting Balloon Angioplasty
Cutting balloon angioplasty for pulmonary artery stenosis was first reported in 199917 and has since been reported in multiple series and studied in a randomized trial comparing cutting balloon angioplasty to high-pressure balloon angioplasty.18 Cutting balloons improve the overall success rate for pulmonary artery angioplasty, particularly for lesions resistant to standard high-pressure balloon dilation. The microsurgical blades of the cutting balloon create precise longitudinal “incisions” along the length of the target lesion. The incisions are formed at lower pressures than those required to create an intimal/medial tear with a standard angioplasty balloon, and thus cutting balloons may reduce the risk of vessel rupture. Results are best in pulmonary artery stenoses that exhibit a discrete waist during standard angioplasty. Success in long-segment stenoses, diffusely hypoplastic pulmonary arteries, and pulmonary arteries exhibiting significant recoil is limited.19
Small diameter, 6-, 10-, and 15-mm long cutting balloons are available from 2.0 mm to 4.0 mm in diameter in 0.25 mm increments (Flextome, Boston Scientific). These are available as both over-the-wire and monorail systems. Importantly, these only accept a 0.014″ guidewire; thus guidewire exchange is frequently required when switching from a standard angioplasty balloon to a small diameter cutting balloon. Large diameter cutting balloons are limited to 2 cm lengths and are available from 5-8 mm in diameter in 1 mm increments. These balloons require a 0.018″ guidewire.
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