Abstract
This chapter focuses on the indications and treatment options of pulmonary valve replacement. Currently there are multiple options for pulmonary valve replacement. However, there is no “perfect” valve for pulmonary position. To date, surgical pulmonary valve replacement followed by transcatheter pulmonary valve replacement is the preferred option to limit future surgical intervention.
Key Words
pulmonary regurgitation, congenital heart disease, congenital heart surgery, pediatrics, cardiovascular
Survival after surgical repair of congenital heart defects has continuously improved over the last several decades with advances in surgical techniques, cardiopulmonary bypass, and perioperative care. This has created the need to address the emerging long-term issues of older children and young adults with “repaired” congenital heart disease. Half of the patients who survive tetralogy of Fallot repair require pulmonary valve replacement (PVR) within 30 years. As a result, PVR or right ventricular outflow tract (RVOT) reconstruction is becoming the most frequent congenital heart surgical procedure performed on adolescents and young adults. More recently there is growing enthusiasm for percutaneously inserted bioprosthetic valves in the pulmonary position. In this chapter we will review the current indications and approach for PVR.
Indications
PVR is required in various situations such as isolated pulmonary valvular disease or pulmonary insufficiency after repair of tetralogy of Fallot ( Box 60.1 ). Current indications for PVR include symptomatic and asymptomatic patients with increased risk for right ventricular (RV) dilation, RV failure, exercise intolerance, arrhythmia, and sudden cardiac death ( Box 60.2 ). Numerous studies have demonstrated the benefits of PVR, and guidelines for PVR in adults with CHD have been published by the American, Canadian, and European cardiac societies. These guidelines are clear in symptomatic patients with severe pulmonary regurgitation recommending PVR. However, they are less clear in asymptomatic patients with severe pulmonary regurgitation. PVR offers improvement in symptoms and RV function, but the sickest patients receive the least benefit and carry higher surgical risks.
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Pulmonary valve stenosis
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Tetralogy of Fallot with or without pulmonary atresia
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Pulmonary atresia with intact ventricular septum
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Truncus arteriosus and other congenital heart defects repaired with an RV-PA conduit
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Post Ross procedure
PA, Pulmonary artery; RV, right ventricle.
Moderate or severe pulmonary regurgitation (regurgitation fraction ≥25%)
- I.
Asymptomatic patient with two or more of the following criteria
- a.
RV end-diastolic volume index >150 mL/m 2 or z score >4. In patients whose body surface area falls outside published normal data: RV/LV end-diastolic volume ratio >2
- b.
RV end-systolic volume index >80 mL/m 2
- c.
RV ejection fraction <47%
- d.
LV ejection fraction <55%
- e.
Large RVOT aneurysm
- f.
QRS duration >140 ms
- g.
Sustained tachyarrhythmia related to right heart volume load
- h.
Other hemodynamically significant abnormalities:
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RVOT obstruction with RV systolic pressure ≥2/3 systemic
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Severe branch pulmonary artery stenosis (<30% flow to affected lung) not amenable to transcatheter therapy
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≥ Moderate tricuspid regurgitation
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Left-to-right shunt from residual atrial or ventricular septal defects with pulmonary-to-systemic flow ratio ≥1.5
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Severe aortic regurgitation
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Severe aortic dilation (diameter ≥5 cm)
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- a.
- II.
Symptomatic patients with one or more of the above criteria
- III.
Special considerations
- a.
In patients who underwent TOF repair at ≥3 years of age, PVR may be considered if fulfill ≥1 of the quantitative criteria in section I.
- b.
In women with severe pulmonary regurgitation and RV dilation and/or dysfunction, PVR may be considered if fulfill ≥1 of the quantitative criteria in section I due to pregnancy-related complications.
- a.
LV, Left ventricle; PVR, pulmonary valve replacement; RV, right ventricle; RVOT, right ventricular outflow tract; TOF, tetralogy of Fallot.
Given the limitations of echocardiography to accurately assess the RV, magnetic resonance imaging (MRI) has become the more preferable approach to assess pulmonary regurgitation fraction, RV volume, and RV ejection fraction. Several MRI studies have reported that RV volumes return to the normal range if the preoperative RV end-diastolic volume (RVEDV) index is less than 150 to 170 mL/m 2 or the RV end-systolic volume is less than 80 to 90 mL/m 2 . Additional findings such as an RV pressure more than two-thirds systemic, a pulmonary-to-systemic flow ratio of more than 1.5 : 1, residual shunt, severe tricuspid regurgitation, an RVOT aneurysm, and reduced left ventricular function are also factors promoting a need for PVR. Maximal benefit from PVR seems to occur with earlier intervention before the RV suffers irreversible change. Although aggressive application of PVR to younger children may result in a higher likelihood of reintervention within 10 years, waiting to perform PVR for preoperative RV end-systolic volume (RVESV) greater than 95 mL/m 2 has an increased risk for suboptimal hemodynamic outcomes and adverse clinical events.
Common candidates for PVR include patients with transannular patches for repair of tetralogy of Fallot, congenital pulmonary valve stenosis, repaired truncus arteriosus, and other anomalies requiring placement of an RV–pulmonary artery (PA) conduit. RV function is more successfully preserved in patients after repair of pulmonary stenosis compared with patients with pulmonary insufficiency following repair of tetralogy of Fallot. Patients with residual pulmonary insufficiency after congenital pulmonary stenosis repair had superior RV remodeling after PVR when compared with tetralogy of Fallot patients with residual pulmonary insufficiency after PVR. In patients requiring PVR, significant tricuspid regurgitation is more common in patients with pulmonary atresia and intact ventricular septum compared with patients with tetralogy of Fallot. Therefore complete knowledge of the original congenital heart defect is extremely important before PVR. In addition to the recommended indications for PVR, the optimal timing for PVR requires a thorough workup and discussion based on the individual patient.
There is agreement that PVR is recommended in symptomatic patients with severe pulmonary insufficiency (particularly with RV dilation), heart failure, and new-onset arrhythmia. However, PVR is still controversial in asymptomatic patients. There is no randomized trial to prove PVR reduces long-term adverse clinical outcomes compared with medical treatment. Multicenter clinical registries will be necessary to assess long-term clinical benefit after PVR.
Pulmonary Valve Replacement Options ( Box 60.3 )
Surgical PVR is becoming one of the most common operations in adult congenital heart disease. The mortality is reassuringly low, reported as 0.9% from the Society of Thoracic Surgeons Congenital Heart Surgery Database (STS CHSD) and 4.1% from the Adult Cardiac Surgery Database (STS ACSD). The risk of a major complication (temporary or permanent renal failure at discharge requiring dialysis, neurologic deficit persisting at discharge, atrioventricular block or arrhythmia requiring a permanent pacemaker, postoperative mechanical circulatory support, phrenic nerve injury, or any unplanned reintervention before discharge) is reported as 2.2% from the STS CHSD and 20.9% from STS ACSD. PVR carries higher morbidity and mortality in the adult population compared with the pediatric population, possibly secondary to a higher prevalence of other preoperative risk factors such as endocarditis. There is also an increasing volume of literature suggesting that the risk for PVR is significantly higher when performed by non–congenital heart surgeons and when patients are cared for in intensive care units that are not accustomed to caring for congenital heart patients. The difference between the mortality for PVR in the STS CHSD and the STS ACSD is likely not due to patient comorbidity alone.
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Allograft
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Bioprosthetic stented valve
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Bioprosthetic stentless valve (Contegra, Freestyle)
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Mechanical valve
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ePTFE valve (monocusp, bicuspid, tricuspid)
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Transcatheter pulmonary valve (Melody, Sapien)
ePTFE, Expanded polytetrafluoroethylene.
Surgical Approach
In the majority of PVR surgeries a repeat sternotomy is necessary. The risk of a reentry injury during repeat sternotomy is low (0.3% to 1.3%) ; however, major injury requires emergent cannulation to initiate cardiopulmonary bypass (CPB). There are clear risk factors that increase the risk of PVR in certain patients such as the existence of a transannular patch, a prior RV-PA conduit, or an enlarged and aneurysmal aorta; however, reentry injury is not associated with an increased risk of operative mortality in the current era.
Typically CPB at normothermia or mild hypothermia is common for PVR. In the case of a residual atrial or ventricular level shunt, aortic cross-clamping with cardioplegic arrest of the heart is preferred over techniques such as “empty, beating” right heart surgery to reduce the risk of systemic air embolism. In general the favored recommendation is to avoid “empty, beating” heart surgery for congenital heart surgery due to the possibility of unrecognized residual shunts, and we recommend aortic cross-clamping and cardioplegic arrest unless the anatomy makes this more dangerous (e.g., a calcified, enlarged, or heavily scarred aorta). Ventricular fibrillation using an electric fibrillator is an alternative technique to avoid “empty, beating” heart surgery, which carries a risk for embolic brain injury in some patients. The pulmonary annulus is visualized through a longitudinal incision to the RVOT. An appropriate-size valve or valved conduit can be chosen, and the selected valve can be placed using a wide variety of surgical techniques.
Allograft.
Allografts ( Fig. 60.1A ) have been widely used for more than 50 years. Early outcomes with allografts have been excellent, especially in neonates and infants; however, valve deterioration over time has been an issue, especially in smaller allografts. Decellularized pulmonary homografts have better early to midterm results when compared with conventional homografts or to bovine jugular vein (BJV) conduits. Freedom from conduit dysfunction was significantly better at 10 years in decellularized pulmonary homografts (83%) compared with conventional pulmonary homografts (58%). However, long-term outcomes beyond 10 years have been discouraging, especially in small children. In some countries such as Japan, allografts are not widely available.
Bioprosthetic Stented Valve.
The durability of bioprosthetic stented valves (see Fig. 60.1B ) in the aortic position over time have greatly improved. When a stented, bioprosthetic valve is used, a patch pulmonary arterioplasty to augment the size of the RVOT can be used to allow placement of an adequate-size prosthesis ( Fig. 60.2 ).
