Pulmonary regurgitation surgical therapy

# Overview
Surgical management of pulmonic regurgitation may include pulmonary valve replacement (PVR). The major indications for PVR may include symptomatic patients with arrythmias or NYHA class higher than II, an ejection fraction of less than 40% when assessed with CMR, patients with progressive right ventricular regurgitation(right ventricular end- diastolic volume 160 mL/m2 or end-systolic volume 82 mL/m2 on CMR), moderate to severe tricuspid valve regurgitation, resulting from annular dilatation, patients at risk of developing arrythmias and with prolonged QRS duration.(total QRS duration 180 msec, or QRS duration increase >3.5 msec per year and severe pulmonic regurgitation among patients with another cardiac lesion that requires operative intervention. Timing of pulmonary valve replacement is not well defined. However timely intervention is advised before the onset of RV dysfunction. Pulmonary valve replacement (PVR) by surgical and percutaneous approach is the definitive treatment for the management of chronic PR and has proven to improve RV function, New York Heart Association Functional Class status, quality of life, and reduce risk for development of RV tachyarrhythmias and sudden cardiac death. Among patients with arrhythmias, intraoperative electrophysiological mapping with cryoablation during pulmonary valve replacement has demonstrated promising results.

# Surgical therapy
Pulmonary valve replacement (PVR) is one of the most common procedures performed among adults with congenital heart disease, due to different diseases causing regurgitation or stenosis. Patients may undergo reoperations during their lifetime.

## Indications for Surgery
Indications for pulmonary valve replacement (PVR) include:
- Symptomatic patients with arrythmias or NYHA class higher than II.
- Ejection fraction of less than 40% when assessed with cardiac MRI. Both right and left ventricular dysfunction  serve as an indication.
- Patients with progressive right ventricular dysfunction (right ventricular end-diastolic volume 160 mL/m2 or end-systolic volume 82 mL/m2 on CMR).
- Moderate to severe tricuspid regurgitation, resulting from annular dilation.
- Patients at risk of developing arrythmias and with prolonged QRS duration.(total QRS duration 180 msec, or QRS duration increase >3.5 msec per year).
- Severe PR in a patient with another cardiac lesion (such as RVOT aneurysm) that requires operative intervention.
- According to ACC/AHA guidelines, PVR is reasonable among adults with the previous TOF, severe PR, and any of the following:
Moderate to severe RV dysfunction/ enlargement
Development of symptomatic or sustained artial and/or ventricular arrhythmias
Moderate to severe TR
- Moderate to severe RV dysfunction/ enlargement
- Development of symptomatic or sustained artial and/or ventricular arrhythmias
- Moderate to severe TR

## Timing Of Surgery
- Timing of pulmonary valve replacement is not well defined as in aortic and mitral regurgitation. However timely intervention is advised before the onset of RV dysfunction.
- Pulmonary valve should be replaced before RV end-diastolic volume-index (EDVI) exceeds 163 mL/m2 or RV end-systolic volume index (ESVI) exceeds 80 mL/m2. RV ESVI is the major factor to be considered.
- Delayed intervention has shown to have poor outcomes and higher rate of re-intervention.
- The prime goals of pulmonary valve replacement include improved functional class and quality of life, maintenance of right (and left) ventricular function, risk modification of arrhythmia and sudden cardiac death.

## Choice of prosthetic valve
- Bioprosthetic valves:
Usually preferred over mechanical valve prosthesis and have a longevity of around 15years.
Bioprosthesis utilizes biological tissue that are usually harvested from the ] of either cows or horses.
Do not require anticoagulation.
Indications: Informed patient's desire or if there are contraindications/high risk to anticoagulation.
- Usually preferred over mechanical valve prosthesis and have a longevity of around 15years.
- Bioprosthesis utilizes biological tissue that are usually harvested from the ] of either cows or horses.
- Do not require anticoagulation.
- Indications: Informed patient's desire or if there are contraindications/high risk to anticoagulation.
- Mechanical valves:
Preferred among patients at high risk of reoperation such as patients with RV dysfunction.
Some of the examples include bileaflet (Carbomedics), titing disc (Medtronic-Hall), and the cage.
Require long-term anticoagulation.
Indications: Age <65-70 years and long life expectancy, informed patient's desire, another heart valve contains a mechanical implant, patient is on anticoagulation already or there are no contraindications to anticoagulation. Patients requiring a redo surgery are high-risk.
- Preferred among patients at high risk of reoperation such as patients with RV dysfunction.
- Some of the examples include bileaflet (Carbomedics), titing disc (Medtronic-Hall), and the cage.
- Require long-term anticoagulation.
- Indications: Age <65-70 years and long life expectancy, informed patient's desire, another heart valve contains a mechanical implant, patient is on anticoagulation already or there are no contraindications to anticoagulation. Patients requiring a redo surgery are high-risk.

## Surgical Options
- Pulmonary valve replacement (PVR) by surgical and percutaneous approach is the definitive treatment for the management of chronic PR and has proven to improve RV function, New York Heart Association Functional Class status, quality of life, and reduce risk for development of RV tachyarrhythmias and sudden cardiac death.
- Surgical repair may combine pulmonary valve insertion with correction of the associated defects such as reduction of aneurysmal RVOT or intraoperative cryoablation.
- The indications for both surgical or transcatheter pulmonary valve replacement are similar.
- In the case of free PR with severe discrepancy (>35%) between right and left pulmonary blood flow, patients should undergo balloon dilation, with/without an endoluminal stent implantation.

### Surgical Valve Implantation
- Various valved conduits are placed to replace the pulmonic valve which include homografts from cadavers, valved conduits, and the contegra bovine jugular vein graft or a bioprosthetic valve implanted directly in the RV outflow tract.
- Stenosis of the conduit is the major limitation and 25% of patients have to undergo a repeat intervention.

### Transcatheter Pulmonary Valve Replacement
- The Melody transcatheter pulmonary valve (Medtronic) was approved by FDA in 2010.
- The current transcatheter valves are designed to treat conduit and bioprosthetic valve failure only.
- For transcatheter valve replacement eligibility, the morphology of RVOT (determined viaCT or MRI) serves as the major criterion. a determination that may easily be made at CT or MRI.
- Contraindications:
Patients with an aneurysmal appearance of RVOT do not qualify for transcatheter pulmonary valve implantation.
They are not useful to treat patients who had a RVOT reconstruction by transannular patching.
- Patients with an aneurysmal appearance of RVOT do not qualify for transcatheter pulmonary valve implantation.
- They are not useful to treat patients who had a RVOT reconstruction by transannular patching.

# Complications
- Complications (both surgical and transcatheter) post pulmonic valve replacement (PVR) include:
Prosthetic valve failure (PVR or interventional catheter procedure is required to be redone).
Prosthetic valve dysfunction (death due to prosthetic valve dysfunction is very rare).
Atrial fibrillation and atrial flutter are rare complications.
Pulmonary artery obstruction.
Infective endocarditis is not a common late complication (reported in 3.2% cases a few months post tPVR). A few patients (such as of streptococcal infection) may be managed medically and surgical or percutaneous reintervention may be required for others. Staphylococcus aureus and Candida albicans are other pathogens commonly involved.
- Prosthetic valve failure (PVR or interventional catheter procedure is required to be redone).
- Prosthetic valve dysfunction (death due to prosthetic valve dysfunction is very rare).
- Atrial fibrillation and atrial flutter are rare complications.
- Pulmonary artery obstruction.
- Infective endocarditis is not a common late complication (reported in 3.2% cases a few months post tPVR). A few patients (such as of streptococcal infection) may be managed medically and surgical or percutaneous reintervention may be required for others. Staphylococcus aureus and Candida albicans are other pathogens commonly involved.
- Complications post transcatheter pulmonic valve implantation (TPVI)/ transcatheter pulmonic valve replacement (tPVR) include:
- Procedural:
tPVR procedural complications range from 2.9%-6% and may warrant conversion to surgery.. They include: valve migration, homograft rupture, guide wire injury to a distal branch pulmonary artery, and damage to the tricuspid valve.
Coronary artery compression due to stent placement
Conduit rupture
- tPVR procedural complications range from 2.9%-6% and may warrant conversion to surgery.. They include: valve migration, homograft rupture, guide wire injury to a distal branch pulmonary artery, and damage to the tricuspid valve.
- Coronary artery compression due to stent placement
- Conduit rupture
- Device-related complications:  Detected postprocedure.
Stent fracture: It leads to an increase in RV outflow tract gradient and RV pressure and its incidence is around 21% in 1 series that used the Melody valve and was the major reason for a repeat intervention.Stent fracture has not been reported with the SAPIEN valve.
Device instability and dislodgement
Valve-in-valve tPVR has been performed to treat the Hammock effect, stent fractures, and residual stenosis.
- Stent fracture: It leads to an increase in RV outflow tract gradient and RV pressure and its incidence is around 21% in 1 series that used the Melody valve and was the major reason for a repeat intervention.Stent fracture has not been reported with the SAPIEN valve.
- Device instability and dislodgement
- Valve-in-valve tPVR has been performed to treat the Hammock effect, stent fractures, and residual stenosis.

## Outcomes
- Patients with percutaneous pulmonary valve replacement have good outcome and are free of reintervention at 1year.
- Patients with CMR derived pre operative right ventricular end diastolic volume index of less than 160ml/m2  and end systolic volume index of less than 80ml/m2 showed better outcomes. 

# Treatment of arrhythmia
- An invasive electrophysiological study to ablate atrial flutter, and map (if not ablate) ventricular tachycardia is recommended among patients with documented atrial flutter or ventricular tachycardia.
- Before a patient reaches endstage heart failure, resynchronization therapy is the suggested treatment for dilated right ventricles with the RBBB.
- Among patients with arrhythmias, intraoperative electrophysiological mapping with cryoablation during pulmonary valve replacement has demonstrated promising results. Complete resolution of preexisting arrhythmias has been reported.