Cardiology

Congenital Intervention - Pulmonary Valve Replacement

General description of procedure, equipment, technique

Transcatheter management of conduit stenosis with bare metal stents has been used to effectively relieve conduit stenosis to delay the need for surgical valve replacement. Unfortunately, bare metal stenting may exacerbate chronic pulmonary insufficiency. More recently, percutaneous PV replacement has become an option to approach this patient population to relieve both conduit stenosis and conduit insufficiency.

Indications and patient selection

The 2008 guideline statement on management of adults with congenital heart disease with either or both severe RV to pulmonary artery conduit stenosis (peak gradient greater than 50 mm Hg or mean greater than 30 mm Hg) or conduit insufficiency; states the following as indications to replace the PV with either surgical or catheter-based intervention (Class I evidence):

  1. Decreased exercise capacity

  2. Presence of right ventricular failure

  3. At least moderate tricuspid insufficiency, or moderately dilated end diastolic RV volume

Contraindications

Vascular anatomy not capable of using the percutaneous equipment needed to deploy the valve. Femoral venous hypoplasia or occlusion is the most common problem with this patient population.

The jugular approach has also been described for some patients. Also, there are reports of placing the valve from a Glenn pathway but reversing the direction on the delivery catheter.

Details of how the procedure is performed

The Melody valve is a bovine jugular vein valve sutured within a platinum iridium stent. It is an 18-mm valve that is crimped to 6 mm and can be in my experience expanded to between 16 and 24 mm. The valve is inserted using a 22 Fr balloon in a balloon catheter delivery system (Ensemble) with a retractable sheath that covers the Melody valve once it is front loaded and crimped over the balloon.

There are three available balloon sizes (18 mm, 20 mm, and 22 mm) and the length of the stent is 26 mm, 24 mm, and 23 mm when dilated to the respective diameters. The suturing of the valve is clear except at the device outflow line, which is blue and aids correct orientation of the device on the delivery system.

Implantation of the Melody valve is typically performed from the femoral approach but can also be performed from the internal jugular or subclavian vein approach. After standard hemodynamics and angiography are performed, balloon sizing and balloon compliance testing can produce further information regarding the dimensions and distensibility of the right ventricular outflow tract.

Coronary anatomy should be defined with particular attention to the relationship of the coronary arteries to the right ventricular outflow tract. Coronary angiography should be performed during simultaneous balloon dilation of the right ventricular outflow tract. This is an important step in the assessment of the patient. During the multicenter trial for Melody there were 6/136 (4.4%) subjects deemed not candidates for pulmonary valve placement due to concerns about coronary artery anatomy.

Subsequently, if there is significant obstruction, predilation with a high-pressure balloon can facilitate passage of the delivery system and also aid in determining the optimal size for stent valve implantation. Since conduit rupture must be considered a risk, having access to a covered stent in the event of an emergency should be arranged.

The majority of procedures now involve prestenting at the implantation site with a bare metal stent, particularly in smaller, more narrowed conduits with more significant obstruction or closer apposition to the anterior chest wall. Prestenting reduces the risk of stent fracture. Some operators advocate for implantation of multiple “stacked” stents until conduit recoil is eliminated. The objective is to eliminate fracture risk.

Interpretation of results

Angiography to determine valve position, pressure data to reach a minimal residual valve stenosis, and follow-up MRI or CT angiography to assess valve function. Echocardiography is also used to follow the mean valve gradient and consider fluoroscopy for assessment of stent fractures when there is suspicion of loss of valve integrity or a type II fracture.

Outcomes (applies only to therapeutic procedures)

Between January 2007 and August 2009, 136 subjects were enrolled in the Melody transcatheter pulmonary valve multicenter trial to assess transcatheter pulmonary valve repair of the right ventricular outflow tract. Successful implant of the valve was achieved in 124 subjects with 8 procedural adverse events including a coronary artery dissection, two with conduit rupture, a ventricular arrhythmia, a hemodynamic derangement, a femoral vein thrombosis, and two with guidewire pulmonary artery perforation.

With a median follow-up of 8.5 months (range: 6 to 24 months), there were 7 subjects with major stent fracture and 10 subjects that underwent reintervention, all transcatheter, and 9 of those were a valve-in-valve procedure.

Alternative and/or additional procedures to consider

Surgical repair of the right ventricular outflow tract. This is often a balance between reoperation risk and transcatheter valve success.

Complications and their management

Serious adverse events and management

Reported procedural and long term adverse events include:

  1. Coronary artery compression - Careful angiography is recommended with valve placement.

  2. Conduit wall rupture or dissection - Covered stents should be available during these procedures.

  3. Branch 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. Hammock effect with poor apposition of the stent Gore-Tex (mainly a problem with early design)

  6. Pulmonary stent valve frame fracture - seen with the Melody but not described with the Edwards

  7. Endocarditis - Current guidelines recommend 6 months SBE prophylaxis post valve placement

What’s the evidence?

These are the key studies for transcatheter pulmonary valve replacement:

Warnes, CA, Williams, RG, Bashore, TM. "ACC/AHA 2008 Guidelines for the management of adults with congenital heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (writing committee to develop guidelines on the management of adults with congenital heart disease)". Circulation. vol. 118. 2008. pp. e714-833.

(This article outlines the guidelines for management of pulmonary outflow conditions.)

McElhinney, DB, Hellenbrand, WE, Zahn, EM. "Short- and medium-term outcomes after transcatheter pulmonary valve placement in the expanded multicenter US Melody valve trial". Circulation. vol. 122. 2010. pp. 507-16.

(This is the multicenter trial results for the Melody valve.)
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