Cardiology

Congenital Intervention - Angioplasty (Pulmonary Arteries and Veins)

General description of procedure, equipment, technique

Angioplasty of the pulmonary arteries

Balloon or stent angioplasty of the branch pulmonary arteries is occasionally necessary for patients with a history of complex congenital heart disease, such as transposition after the arterial switch operation and with tetralogy of Fallot.

Branch pulmonary artery obstructions may be isolated, multiple, or may occur diffusely throughout the pulmonary arteries.

Postmortem studies have revealed these lesions to consist of primarily fibrous intimal proliferation with medial hypoplasia and loss of elastic fibers in affected vascular segments. For adult congenital heart patients, the isolated obstruction of the proximal branch is rare, but when it does occur it is more often the result of prior surgical interventions, Blalock-Taussig shunt, or main pulmonary artery banding.

Multiple, or diffuse narrowing of the branch pulmonary arteries (PAs), especially in conjunction with other cardiac and/or systemic malformations, is a marker for congenitally acquired genetic or infectious diseases.

William syndrome, Noonan syndrome, congenital rubella, and Alagille syndrome all commonly present with branch PA stenosis and/or hypoplasia. It is rare that these systemic diseases remain undiagnosed into adulthood.

Angioplasty of the pulmonary veins

Pulmonary vein stenosis after radiofrequency ablation for atrial fibrillation is uncommon but can occur. Although further follow-up is necessary to determine long-term success, stent angioplasty can improve pulmonary vein flow. Also, most of these patients will have symptomatic improvement dilation of postablation pulmonary vein stenoses.

Indications and patient selection

Angioplasty of the pulmonary arteries

Diminished flow to the branch vessel to less than 20%, less than 50% of the expected adult branch pulmonary artery diameter, or less than 50% of the normal opposite branch.

Indications for catheter intervention include symptoms, a significant decrease in pulmonary blood flow to one lung based on perfusion data suggesting less than 20% flow, or elevated right ventricular (RV) afterload as determined by a ratio of RV systolic to systemic systolic pressure.

Angioplasty of the pulmonary veins

The median onset of symptoms after radiofrequency ablation is reported as 7.5 weeks (range, 0.1 to 48). The median duration from the onset of symptoms to definitive diagnosis of pulmonary vein stenosis is reported as 16 weeks (range, 2 to 59). Often, patients are initially misdiagnosed with either pneumonia, new-onset asthma, pulmonary embolism, and/or lung cancer.

Because of the incorrect diagnosis, patients may undergo placement of an inferior vena cava (IVC) filter, partial resection of the lung, or other unnecessary procedures.

Contraindications

Angioplasty of the pulmonary arteries

No specific contraindications unless the stent is to obstruct another branch. Caution should be considered if there is an abnormal wall anatomy, such as with some cardiovascular syndromes or surgically created branch pulmonary vessels from aortopulmonary collaterals or pericardial tissue.

Angioplasty of the pulmonary veins

Although there are not true contraindications for this procedure, there are patients with difficult transseptal access or total occlusion of the pulmonary vein that the procedure may not be successful.

Details of how the procedure is performed

Angioplasty of the pulmonary arteries

Current techniques have been best applied to isolated lesions, and involve balloon angioplasty, stent angioplasty, and the use of cutting balloons when standard balloons have failed. Improvements in stent and balloon design have allowed the percutaneous approach to be applied to almost all patients with the delivery of large stents that can be dilatable to 18 mm in diameter.

Angioplasty of the pulmonary veins

Procedures are usually performed with patients under general endotracheal anesthesia due to the risk of vein injury and airway bleeding and access is obtained in both femoral veins. Patients are given 5000 units of intravenous heparin.

Activated clotting times (ACT) are monitored throughout the procedure with the goal to maintain an ACT above 250 units. Right heart hemodynamic data are obtained with a 7 Fr balloon wedge catheter through the left femoral sheath.

This catheter is also used to obtain pulmonary artery wedge pressure and perform a wedge angiogram for mapping the individual pulmonary vein flow and to determine if any segments were completely occluded.

Subsequently, transseptal puncture is performed to access the left atrium and pulmonary veins. A V-18 floppy-tipped control wire (Boston Scientific) is manipulated across the target lesion within the pulmonary vein and a F Angled Glide catheter (Medi-tech, Boston Scientific) is coaxially introduced and used to measure a mean pressure gradient across the target lesion, angiographically study individual pulmonary vein anatomy, and position the V-18 wire into the distal pulmonary vein.

The diameter and length of the target lesion and the distal pulmonary vein are measured digitally using the diameter of the catheter across the target lesion as a known diameter. Standard angioplasty is performed in each lesion first to determine the resistance of the vein.

The angioplasty balloon used should not exceed the diameter of the stenotic lesion by a factor of 4 or the distal pulmonary vein by a factor of 1.5. The lesion is then gradually dilated with a goal of a final diameter greater than 12 mm.

After balloon angioplasty, a mean pressure gradient across the lesion is measured and angiography is used to measure the target lesion diameter and assess the degree of vessel injury. Then stent angioplasty is performed if a stent diameter of greater than 10 mm can be achieved and there are no distal branches that are at risk to be jailed.

Also, difficult anatomy such as bilateral proximal branch stenosis with closely related ostia can also be treated with the percutaneous approach using special techniques.

Interpretation of results

Angioplasty of the pulmonary arteries

Usual goal is to diminish right ventricular hypertension and/or enhance flow to the lung fields. Echocardiography or cardiac MRI are used to assess these results and compare with the preintervention data.

Angioplasty of the pulmonary veins

Restenosis does occur and many patients return for further dilation of the stent at 6 months follow-up. The decision to return to the laboratory can be based on symptoms or further assessment by perfusion scan, CT angiography, or cardiac MRI.

Outcomes (applies only to therapeutic procedures)

Angioplasty of the pulmonary arteries

Although the outcomes are generally good if procedural serious adverse events are avoided, the outcomes in patients with diffuse pulmonary obstructions, such as William, Noonan, Rubella and Alagille syndromes, have been generally poor. This can be attributed to two factors.

First, given the large number of vessels typically involved, successful dilation of even a few significant lesions will not result in an immediate decrease in right ventricular afterload. Second, when angioplasty is successful, the newly unobstructed lung segment will acutely face high flow, as blood is redirected from unobstructed segments, as well as high pressure. This may result acutely in a “reperfusion injury” with significant segmental pulmonary edema, which may require ventilatory support.

Angioplasty of the pulmonary veins

At least 85% of patients will need further dilation of the stent due to excessive endothelial growth within the stent frame and along the distal entrance of the stent by 6 months follow-up. If further dilation can be achieved above 10 to 12 mm there is a better chance that additional interventions will not be necessary. Vessels under this diameter will often require redilation every 1 to 3 years or the patient becomes use to the fact that this vessel will never have normal flow.

Alternative and/or additional procedures to consider

Angioplasty of the pulmonary arteries

Intraoperative stent placement or surgical arterioplasty. Although most proximal stenoses of the prehilar area can be repaired surgically, more distal branch pulmonary artery obstructions are difficult for the surgeon to reach without the potential for extensive pulmonary parenchymal injury. As a result, branch PA stenosis in these locations is better treated in the catheter laboratory or by intraoperative stent angioplasty.

Angioplasty of the pulmonary veins

  • Medical management

  • Surgical repair of the pulmonary veins

Complications and their management

Serious adverse event and management

Angioplasty of the pulmonary arteries

Reported procedural and long-term adverse events include:

  1. Coronary artery compression - Careful angiography recommended prior to stent placement

  2. Pulmonary artery rupture or dissection - Covered stents should be available during these procedures

  3. Distal pulmonary artery perforation - mainly an issue with the stiff wire in the pulmonary arteries.

  4. Malposition of the stent valve or embolization into the RV or pulmonary arteries

  5. Pulmonary stent fracture - Seen with these and may require a second stent procedure

  6. Endocarditis - Current guidelines recommend 6 months subacute bacteriial endocarditis (SBE) prophylaxis poststent placement

Angioplasty of the pulmonary veins

Qureshi and colleagues reported no procedure-related deaths in 2003, but four adverse events, including two events of pulmonary hemorrhage after the balloon wedge angiogram in the setting of an occluded pulmonary vein. Immediately after a balloon wedge angiogram, one patient had hemoptysis that resulted in 48 hours of intubation and positive-pressure ventilation before complete resolution, and self-limiting pulmonary hemorrhage developed in one patient.

In addition, one patient had a pulmonary vein tear that required emergent surgical repair, and one patient had an embolic event with MRI evidence of middle cerebral artery distribution stroke and transient ECG changes.

What’s the evidence?

Angioplasty of the pulmonary arteries

This is a key study for transcatheter management of pulmonary artery stenoses:

Gonzalez, I, Kenny, D, Slyder, S, Hijazi, ZM. "Medium and long-term outcomes after bilateral pulmonary artery stenting in children and adults with congenital heart disease". Pediatr Cardiol.. vol. 34. 2013. pp. 179-84.

(This article reviews the outcome for stent angioplasty of the branch pulmonary arteries.)

Angioplasty of the pulmonary veins

This is a key study for transcatheter management of pulmonary vein stenosis:

Qureshi, AM, Prieto, LR, Latson, LS. "Transcatheter angioplasty for acquired pulmonary vein stenosis after radiofrequency ablation". Circulation. vol. 108. 2003. pp. 1136-1342.

(This article reviews the technique and outcome for angioplasty of stenotic pulmonary veins after atrial fibrillation ablation.)
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