SECTION VII - RIGHT VENTRICULAR OUTFLOW TRACT OBSTRUCTION

Part I - Background Information

Supravalvar RVOTO seldom occurs in isolation. It may occur in tetralogy of Fallot, Williams syndrome, Noonan syndrome, VSD, arteriohepatic dysplasia or congenital Rubella syndrome.

Valvar RVOTO, the most common form of RVOTO, is almost always congenital in origin. Typically, the stenotic pulmonic valve is a thin, pliable, dome-shaped structure, with a narrow opening at its apex. In 10-15% of cases, the valve is dysplastic with thickened and immobile cusps. In adults, the valve may calcify late in life.

Subvalvar (infundibular) RVOTO usually occurs in combination with other lesions, particularly ventricular septal defect, and as part of tetralogy of Fallot.

A separate but somewhat similar entity is "double-chambered right ventricle" with mid-cavity obstruction, often from a prominent moderator band. This may be associated with a VSD.

RVOTO (either valvar or subvalvar) may rarely occur in association with subaortic stenosis.

Branch pulmonary artery stenosis is not considered here.

Hemodynamic Severity Grading

The following is based on peak systolic pressure gradients at heart catheterization). It is time-honoured and useful for decisions regarding therapy.

Trivial: < 25 mmHg
Mild: 25-49 mmHg
Moderate: 50-79 mmHg
Severe or Critical: > 80 mmHg

 
Part II - Prevalence and Genetics

Patients with Noonan syndrome (autosomal dominant inheritance) may present with pulmonary stenosis, ASD and restrictive cardiomyopathy. Mental retardation, abnormal facies, short stature, thoracic/penile and/or testicular abnormalities may also be present. Williams syndrome is a contiguous gene syndrome associated with cardiac (pulmonary stenosis, pulmonary artery stenosis, supravalvar aortic stenosis), neurodevelopmental (mental retardation, "cocktail personality") and multisystem manifestations (abnormal facies, short stature, hypercalcemia) caused by a deletion at chromosome 7q11.23. Patients with Alagille syndrome (autosomal dominant inheritance - also called arteriohepatic dysplasia) may have pulmonary stenosis, pulmonary arterial stenosis and abnormal facies (prominent overhanging forehead, deep-set eyes, small pointed chin).

 
Part III - History and Management of Unoperated Patients

Supravalvar RVOTO may progress in severity and should be monitored.

Patients with trivial valvar RVOTO who are asymptomatic do not become worse with time as adults and will not require treatment, unless endocarditis occurs.
Grade: C	Level: IV	Ref: 89

Female patients often present to physicians during pregnancy because of an increase in the loudness of the murmur. Others may present because of enlarged pulmonary arteries detected on chest x-ray.

Mild valvar RVOTO may progress in 20% of unoperated patients. Moderate stenosis may progress in up to 70% of unoperated patients. Some of these patients will also become symptomatic later in life because of atrial arrhythmias. When the gradient is moderate to severe or the patient is symptomatic, balloon valvotomy (or rarely surgical valvotomy) is recommended.
Grade: C	Level: IV	Refs: 89,90

Subvalvar RVOTO usually progresses in severity and often leads to the development of worsening right ventricular hypertrophy, symptoms, and critical gradients requiring surgical repair.

 
Part IV - Diagnostic Work Up

An adequate diagnostic workup:

• Documents the level(s) of obstruction.
• Quantitates the severity of the obstruction(s).
• Identifies associated abnormalities such as ASD, PDA, VSD and tetralogy of Fallot.

The diagnostic workup should include at a minimum:

• A thorough clinical assessment, paying particular attention to the 'a' wave on the venous pulse, the length of the murmur, the pulmonary component of the second sound and right ventricular hypertrophy.
• ECG.
• Chest x-ray, paying particular attention to valvar calcification on the lateral film.
• Echo Doppler examination by an appropriately trained individual.

The diagnostic workup may require:

• Oximetry (rest and exercise) to determine if there is cyanosis because of associated abnormalities (ASD or VSD).
• Heart catheterization (including angiocardiography) to assess hemodynamics and severity of obstruction and pulmonary artery abnormalities.
• Coronary angiography in patients at risk of coronary artery disease, or in patients over the age of 40 years in whom intervention is being planned.
• MRI to assess associated lesions such as pulmonary artery stenoses, co-existing pulmonary regurgitation and RV function if unable to properly assess these by echo or angiogram.

 
Part V - Indications for Intervention/Re-intervention

Intervention is indicated if: The combined pullback gradient at cath across the RVOT is > 50 mmHg at rest. Symptoms are present (exertional dyspnea, angina, presyncope or syncope).
Grade: C	Level: IV	Ref: 89

Intervention is also indicated if: There are important arrhythmias (usually sustained atrial flutter). There is an associated ASD or VSD, especially if there is right-to-left shunting. There is a double chambered right ventricle with significant mid-cavity obstruction (pullback gradient at cath > 50 mmHg)
Grade: Consensus	Level: IV	Ref: 91

Intervention may be indicated following an episode of endocarditis. Re-intervention is indicated for: Recurrent RVOTO after prior surgery or balloon valvotomy (same criteria as above). Severe pulmonic regurgitation associated with reduced exercise capacity of cardiovascular cause or deteriorating right ventricular function or substantial tricuspid regurgitation or sustained atrial flutter/fibrillation or sustained ventricular tachycardia.
Grade: C	Level: V	Ref: 92

 
Part VI - Surgical/Interventional Options

Balloon valvuloplasty is the treatment of choice for valvar RVOTO. Occasionally valve replacement may be necessary.
Grade: C	Level: IV	Refs: 93,94

Balloon valvuloplasty for valvar RVOTO is an established technique but should still be performed only in centres and by teams with experience in this technique.
Grade: Consensus		Refs: 93,94

Relief of obstruction in a double-chambered right ventricle is accomplished by surgical resection of right ventricular muscle bands. Patients who require operation for supravalvar or subvalvar RVOTO should be operated on by congenital heart surgeons.
Grade: C	Level: V	Refs: 18,19

 
Part VII - Surgical/Interventional Outcomes

The long-term results of surgical pulmonary valvotomy are established. Clinical outcomes are excellent. Relief of valvar RVOTO is usually maintained, but residual obstruction may progress. Occasionally pulmonary regurgitation may progress and become severe enough to warrant re-intervention. Long-term survival in surgical patients when valvar RVOTO occurs as an isolated lesion is close to normal. Long-term mortality may be increased, however, with greater age (> 21 years) at time of surgery.

Patients treated with balloon valvuloplasty, in the absence of a dysplastic valve, have the same prognosis as those who have had surgical valvotomy, at least in the medium term (95,96).

Subvalvar and supravalvar RVOTO seldom recur after adequate repair.

 
Part VIII - Pregnancy

The increased hemodynamic load of pregnancy may precipitate right heart failure, atrial arrhythmias, or tricuspid regurgitation in patients with significant RVOTO, irrespective of the presence or absence of symptoms prior to pregnancy. Patients with moderate-to-severe RVOTO should, therefore, be considered for RVOTO relief prior to conception.

Balloon valvuloplasty for valvar pulmonary stenosis may be employed during pregnancy if the stenosis is severe or symptoms due to pulmonary stenosis develop. When possible, intervention should be delayed until after organogenesis.

Mild RVOTO or RVOTO which has been alleviated by valvuloplasty or surgery (with or without pulmonary regurgitation) is well tolerated.

 
Part IX - Follow Up

Patients with trivial RVOTO (gradient < 25mmHg) do not require ACHD cardiology follow-up. Follow-up by a general physician and/or internist/cardiologist is sufficient unless new findings or symptoms occur. Patients with mild or greater RVOTO or moderate to severe pulmonary regurgitation require monitoring by an ACHD cardiologist as intervention may be required. Particular attention should be paid to: Progressive/recurrent stenosis, especially at the subvalvar level. Right ventricular size and function in the context of significant pulmonary/subpulmonary stenosis and/or regurgitation. Tricuspid regurgitation (often reflecting right ventricular dysfunction). Atrial and occasionally ventricular (usually post-operative) arrhythmias (sustained). Evidence of intracardiac shunting, especially right-to-left. Endocarditis prophylaxis is recommended.
Grade: Consensus