Pulmonic Stenosis

Joseph Heaton; Chris Kyriakopoulos

Pulmonic Stenosis

Continuing Education Activity

Pulmonic stenosis is a typically benign condition in most patients. While generally non-life-threatening after the neonatal period, complications and new-onset symptoms may arise in adults requiring intervention. This activity describes the evaluation and treatment of pulmonic stenosis and highlights the role of the healthcare team in improving care for patients with this condition.

Objectives:

Describe the pathophysiology of pulmonic stenosis.
Review the common presentation of a patient with pulmonic stenosis.
Identify treatment considerations and common complications of interventions for patients with pulmonic stenosis.
Explain the importance of improving care coordination amongst the interprofessional team to improve outcomes for patients affected by pulmonic stenosis.

Introduction

Pulmonic stenosis is a defect of the pulmonic valve in which the valve is stiffened, causing an obstruction to flow. This disease is typically congenital, benign, and diagnosed in pediatric patients with potentially curative treatments. Pulmonic stenosis is also present in adults, usually in conjunction with severe cardiac structural diseases.

Etiology

Pulmonic stenosis is commonly associated with congenital structural cardiac syndromes, including tetralogy of Fallot and Noonan syndrome.[1][2][3] Maternal rubella syndrome is also a common cause of congenital pulmonic stenosis, albeit it is not a genetic-based defect.[4][5] The onset of symptomatic pulmonic stenosis in adults may be seen in pregnancy of patients with undiagnosed pulmonic stenosis, or patients suffering from an underlying carcinoid syndrome.[6][7][8] Furthermore, patients with rheumatic heart disease, previous cardiothoracic surgeries, or a cardiac tumor may acquire pulmonic stenosis.

Epidemiology

Pulmonic stenosis accounts for 7%-10% of the congenital heart diseases.[9][10] There is a slight female predominance, and 2% of familial occurrences are without a genetic cause.[11]

Pathophysiology

Isolated pulmonic stenosis is divided in to valvular, subvalvular, and supravalvular obstruction.

Valvular pulmonic stenosis is the most common type. In typical valvular disease, the commissures are partially fused, and leaflets are thin. This structural anomaly results in a dome-shaped or conical outlet seen during systole.[12] Less commonly, the pulmonic valves can be dysplastic, thickened, and without fusion. The associated hypoplastic annulus and proximal pulmonary artery are common in atypical presentations and are also associated with Noonan syndrome.[13] The atypical presentation generally requires intervention in the early years of life. Bicuspid valves are associated with tetralogy of Fallot, while other variations in leaflet quantities, such as quadricuspid valves, have also been reported.[13]

Subvavular pulmonic stenosis is a defect obstructing the infundibular region. A primary cause of fibromuscular narrowing of the right ventricular outflow tract may be associated with a double-chambered right ventricle or tetralogy of Fallot.[14] Secondary causes of subvalvular pulmonic stenosis may be a result of primary valvular stenosis, inducing hypertrophy of the right ventricle. Secondary stenosis often regresses with valvotomy or valvuloplasty.[14][15][16]

Supravalvular pulmonic stenosis, also known as peripheral pulmonary stenosis, is a functional obstruction originating from the pulmonary artery. The blockage may occur at the main artery, bifurcation point, at distal branches of the pulmonary artery, or any combination thereof. Supravalvular stenosis is associated with structural defects of atrial septal defects, ventricular septal defects, patent ductus arteriosus, and tetralogy of Fallot. Supravalvular stenosis may also be a result of surgical repair of transposition of the great arteries.

History and Physical

Most patients with pulmonic stenosis are asymptomatic, which may lead to a missed diagnosis until an insult occurs. Symptomatic patients typically experience dyspnea on exertion or associated fatigue, depending on the severity of obstruction and cardiac compensatory reserve. Rarely, patients can experience angina or sudden cardiac arrest. In patients with an associated septal defect, the patient may present with signs of cyanosis.

A physical exam may reveal multiple signs of pulmonic stenosis, depending on severity and practitioner skill. Cardiac examination may reveal a left parasternal heave, secondary to right ventricular hypertrophy. Auscultation at the left upper sternal border may reveal a systolic ejection murmur radiating to the back.[17] Furthermore, there may be an associated ejection click and a split S2, rising from a delay in pulmonary closing.[18][19] Finally, pulmonic auscultation may be associated with a 4th heart sound and tricuspid regurgitation.[20][21]

Evaluation

Evaluation of pulmonic stenosis is best completed using echocardiography, due to its superior visualization of the pulmonic valve and surrounding structures.[22][23][24][25] A transthoracic echocardiogram is sufficient in most cases. Transesophageal echocardiography should be reserved for suboptimal views or when particularly assessing for endocarditis.[26][27]

Doppler studies using echocardiography provides flow gradients, which is used to grade severity. Guidelines from the European Association of Echocardiography, the American Society of Echocardiography, the American Heart Association, and American College of Cardiology (AHA/ACC) and the European Society of Cardiology have been summarized below.[22][23][28][29][30][31][32]

Mild stenosis: Peak doppler gradient across the valve <36 mm Hg, doppler jet velocity <3m/sec, or peak doppler gradient <30 mm Hg.
Moderate stenosis: Peak doppler gradient across the valve 36 to 64 mm Hg, doppler jet velocity 3 m/sec to 4m/sec, or peak doppler gradient 30 to 50 mm Hg.
Severe stenosis: Peak doppler gradient across the valve >64 mm Hg, doppler jet velocity >4m/sec, or peak doppler gradient >50 mm Hg.

Pulmonic stenosis may be interpreted through electrocardiography, despite not being diagnostic. Criteria supporting right ventricular hypertrophy correlates well with the severity of the disease. Right axis deviation may also be seen in mild disease, while prominent R waves in V1 and R waves in AVR are more likely seen in severe cases.

Cardiac catheterization and pulmonary angiography are typically not required for the diagnosis of pulmonic stenosis due to echocardiography's efficacy and safety profile. Cardiac magnetic resonance imaging (CMR) is a viable alternative to echocardiography. In the setting of suboptimal echocardiographic viewing or complicated anatomy, cardiac magnetic resonance imaging may assist in proper diagnosis.[33][34] CMR also provides a measurement of the right ventricular volume, right ventricular function, and pulmonary artery blood flow.[35][36][37] Cardiac computed tomography (CCT) may be substituted for patients who cannot undergo CMR.

The sensitivity of plain film x-rays is not sufficient to diagnose pulmonic stenosis. Radiographic evidence of pulmonic stenosis is supported by the prominence of the pulmonary arteries or a prominent right heart border.

Treatment / Management

The American Heart Association and American College of Cardiology have recommended the following management plans in their 2008 guidelines:[28]

Asymptomatic patients with peak doppler gradient <30 mm Hg can be followed up every five years with an electrocardiogram and doppler echocardiography.
Asymptomatic patients with peak doppler gradient >30 mm Hg can be followed up every two to five years with doppler echocardiography.
Asymptomatic patients with peak doppler gradient >60 mm Hg are recommended for balloon valvotomy.
Symptomatic patients with a peak doppler gradient >50 mm Hg and a domed pulmonic valve are recommended for balloon valvotomy.

Surgical intervention is recommended for severe valvular stenosis with severe pulmonary regurgitation, hypoplastic pulmonary annulus, subvalvular stenosis, or supravalvular stenosis. Unfortunately, balloon valvotomy is not as effective in dysplastic valves as in domed valves, making surgery the preferred option. Balloon valvotomy may be worthwhile if peak doppler gradient is >60 mm Hg in asymptomatic patients, or if peak doppler gradient is >50 mm Hg in symptomatic patients. Surgery should also be considered in patients undergoing concurrent cardiac surgical procedures. Pulmonary artery balloon angioplasty, with optional stent placement, is an acceptable treatment for supravalvular and subvalvular pulmonic stenosis.

Differential Diagnosis

Congenital structural cardiac defects include complex congenital heart disease associated with findings of pulmonary stenosis, double-chambered right ventricle, syndrome of absent pulmonary valves, and tetralogy of Fallot. Adult-onset symptoms, excluding undiagnosed congenital causes, include rheumatic valvular heart disease and carcinoid heart disease. Acute onset of symptoms should include myocardial infarction, pulmonary embolism, right heart failure, cardiac tumor, cardiac sarcoma, sinus of Valsalva aneurysm.

Prognosis

The prognosis for most patients is excellent. Except for critical stenosis during the neonatal period, most patients will live a typical life.[38] For patients undergoing surgical revision, 67% of patients achieve 90% of maximal exercise capacity, with only 15-20% needing reintervention. 67% of reinterventions are for significant pulmonary regurgitation, and, if present, most supraventricular tachycardias (SVTs) resolved with reintervention.[39][40]

For patients undergoing balloon valvotomy, a better prognosis was seen with dome-shaped valves over dysplastic valves. After the procedure, at years 1, 3, and 6, the reintervention rate was 0%, 3.5%, and 3.5%, respectively.[41][42] Furthermore, 52% of adults were free of any symptoms.[43] Complications are generally minor but could include a vagal response, catheter induced ventricular ectopy, right bundle branch block, and transient or permanent high-grade AV nodal block.[44] A rare but serious side effect has been seen, dubbed "suicidal right ventricle," in which the infundibulum obstructs the right outflow tract; this may self-resolve or require reintervention.[43][45][46]

Patients suffering from pulmonic stenosis can also undergo virtually all dental procedures. Antibiotics are only recommended with a history of prior endocarditis or a prosthetic valve placement.[47] In pregnancy, patients should avoid vigorous exercise, especially in the second half, when they have moderate or severe gradients. Finally, in athletes with mild stenosis and gradients less than 50 mm Hg, there are no activity limitations; more severe cases should only participate in low-intensity competitive sports.

Complications

Complications of pulmonic stenosis are rare. Infective endocarditis is possible; however, it is the lowest likelihood of all valvular pathologies at 0.38 per 10,000 person-years.[48][49] Other complications include arrhythmias, typically as premature atrial contractions, premature ventricular contractions, and ventricular couplets.[50][51][52]

Consultations

In the setting of pregnancy, a high-risk obstetrician should be consulted as the hemodynamic changes associated with pregnancy can exacerbate pulmonic stenosis symptoms. Cardiology consultation for a pregnant patient may be warranted if the symptoms are severe. Consult of a pediatric cardiologist is warranted for newborns experiencing symptoms of pulmonic stenosis. Depending on the severity, pediatric critical care may also be necessary. In cases of suspected symptomatic pulmonic stenosis in an adult, a cardiology consult may be warranted.

Deterrence and Patient Education

Parents of patients diagnosed with pulmonic stenosis should be educated about complications and treatments available to pediatrics patients. Adult patients, especially those who are planning to become pregnant, should be educated about the risk of such decisions exacerbating their underlying condition.

Enhancing Healthcare Team Outcomes

An interprofessional team approach will ensure the best outcome during pregnancy and labor for patients with pulmonic stenosis. Obstetricians and cardiologists should be in communication for the affected mother's health, as well as with a pediatric intensivist and cardiologist for the affected neonate.

Contributed by Katherine Humphries

Article Details

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