Pulmonary Stenosis

Pulmonary stenosis is a valvular disease characterized by an obstruction to blood flow from the right ventricle to the pulmonary artery, due to a localized narrowing at the level of the pulmonary valve or, less commonly, above or below it (supravalvular and subvalvular forms).

In adults, pulmonary stenosis is a relatively rare condition and in most cases represents the persistence of a congenital anomaly rather than an acquired pathology. Isolated congenital forms or those associated with syndromic malformations are discussed in detail in the section dedicated to congenital heart diseases (Congenital Pulmonary Stenosis). Here, the focus is on residual or acquired forms in adulthood, their pathophysiological implications, and diagnostic-therapeutic strategies.

Etiology, Pathogenesis and Pathophysiology

The most common form of pulmonary stenosis is the congenital valvular type, where the semilunar cusps are thickened, fused, or dysplastic, preventing full opening during systole. In other cases, the narrowing affects the right ventricular outflow tract (subvalvular) or is due to narrowing of the pulmonary artery or its main branches (supravalvular).

Acquired forms, which are extremely rare, include:

• Rheumatic stenosis, almost always associated with other valvular diseases;
• Infective endocarditis involving the pulmonary valve (e.g., in patients with central venous catheters or intravenous drug users);
• Carcinoid heart disease, where serotonergic metastases predominantly affect the right-sided valves;
• Iatrogenic stenosis, secondary to surgery or placement of prosthetic valves or conduits in the right ventricular outflow tract (e.g., post-tetralogy of Fallot repair);
• Radiation-induced stenosis, in patients who underwent mediastinal radiotherapy.

Pulmonary valve stenosis creates a mechanical obstacle to systolic ejection from the right ventricle, resulting in increased right ventricular systolic pressure. This pressure overload induces an adaptive concentric hypertrophy of the right ventricle, which initially maintains pump function. Over time, however, increasing myocardial stiffness impairs diastolic filling, leading to upstream pressure increases and hemodynamic decompensation.

When the pressure gradient exceeds 50–60 mmHg, the stenosis is considered severe. The reduced flow to the pulmonary circulation leads to decreased left cardiac output and systemic oxygenation. Right atrial dilation, associated with rising systemic venous pressures, can eventually cause venous congestion with peripheral edema, hepatomegaly, ascites, and in advanced stages, anasarca.

If a patent foramen ovale or atrial septal defect is present (allowing right-to-left shunting due to elevated right atrial pressure), cyanosis may occur, especially during exertion or when pulmonary resistance increases.

Clinical Manifestations

The clinical manifestations of pulmonary stenosis depend on the severity of the obstruction, the compensatory capacity of the right ventricle, and the presence of associated cardiac abnormalities. In mild forms, the patient may remain asymptomatic for a long time, with the diagnosis made incidentally in adulthood. Symptom onset is related to disease progression and the development of right ventricular dysfunction or systemic hypoxemia.

Main symptoms include:

• Exertional dyspnea, due to reduced left cardiac output secondary to right ventricular ejection limitation;
• Fatigue and weakness, even in the absence of overt heart failure;
• Atypical chest pain or tightness, due to ischemia of the hypertrophic right ventricle;
• Palpitations, related to atrial arrhythmias secondary to right atrial dilation;
• Syncope, rare but possible in severe forms during exertion.

In critical stenosis with right-to-left shunt, central cyanosis may appear, more evident during physical exertion.

Physical examination may reveal:

• Prominent jugular pulse, with accentuated a wave and slow y descent;
• Systolic murmur of variable intensity, harsh and rough, heard at the left second intercostal space near the sternum, radiating upward toward the clavicle or right carotid artery;
• Systolic ejection click, present in valvular forms with mobile cusps;
• Signs of systemic venous congestion in advanced cases: hepatomegaly, peripheral edema, ascites, anasarca.

Diagnosis

Diagnosis is based on a combination of clinical, instrumental, and imaging data, aimed at determining the site, severity, and hemodynamic impact of the stenosis.

Electrocardiogram may be normal in mild forms. In moderate to severe cases, findings include:

• Right ventricular hypertrophy: prominent R waves in V1, right axis deviation, inverted T waves in right precordial leads;
• Peaked P waves ("P pulmonale") due to right atrial dilation;
• Atrial arrhythmias or atrial flutter in advanced stages.

Chest X-ray may show post-stenotic dilation of the pulmonary trunk, reduced peripheral pulmonary vascularization in severe cases, and enlargement of the right atrium and ventricle.

Transthoracic echocardiography is the first-line diagnostic test and is essential to confirm the diagnosis, assess valve morphology, mobility and calcifications, right ventricular wall thickness and hypertrophy, right atrial dilation, and associated valvular regurgitation. Doppler integration allows:

• Measurement of the transvalvular pressure gradient;
• Assessment of flow velocity across the valve;
• Estimation of valve area in complex cases;
• Evaluation of right ventricular function.

Cardiac catheterization is indicated in selected cases, particularly preoperatively or when precise hemodynamic information is needed. It allows direct measurement of the pressure gradient between the right ventricle and pulmonary artery and assessment of vasodilator response in doubtful cases or with associated pulmonary hypertension.

Treatment

Treatment of pulmonary stenosis depends on the severity of the transvalvular pressure gradient, the presence of symptoms, and valve morphological abnormalities. Mild and asymptomatic stenoses do not require active treatment but regular echocardiographic follow-up.

Balloon percutaneous valvuloplasty is the first-line treatment for isolated valvular forms, especially congenital, with favorable anatomy and no significant calcifications. Performed via the femoral vein, this procedure allows commissural dilation with significant gradient reduction. Selection criteria include:

• Severe stenosis (gradient >50 mmHg), even without symptoms;
• Moderate symptomatic stenosis (gradient >30 mmHg);
• Absence of significant pulmonary regurgitation or extensive calcifications.

In cases of dysplastic or calcified valves, complex associated lesions, or valvuloplasty failure, cardiac surgery is required, including commissurotomy or valve replacement with biological prostheses or valved conduits (especially in pediatric patients with complex congenital heart disease).

Medical therapy is reserved for inoperable patients or those awaiting surgery and aims to control right heart failure symptoms through:

• Diuretics for managing systemic congestion;
• Oxygen therapy in patients with hypoxemia and right-to-left shunt;
• Endocarditis prophylaxis in selected cases, especially with prosthetic material or a history of endocarditis.

Complications

The main complications of untreated or advanced pulmonary stenosis are related to progressive right ventricular dysfunction and the development of chronic right heart failure. These include:

• Right atrial dilation with predisposition to supraventricular arrhythmias (flutter or atrial fibrillation);
• Chronic venous congestion with congestive hepatomegaly, ascites, anasarca, and hepatorenal syndrome in advanced cases;
• Infective endocarditis, rarer than in left-sided valvular diseases, but still relevant in at-risk patients;
• Chronic cyanosis in patients with persistent right-to-left shunt through patent foramen ovale or associated septal defects.

Severe pulmonary stenosis left untreated, even if initially well tolerated, may insidiously progress to irreversible right heart failure. Early diagnosis and proper echocardiographic assessment allow for effective treatment and significantly improve prognosis.

References
1. Otto CM, et al. 2020 ACC/AHA Guideline for the Management of Patients With Valvular Heart Disease. Journal of the American College of Cardiology. 2021;77(4):e25–e197.
2. Baumgartner H, et al. 2021 ESC/EACTS Guidelines for the management of valvular heart disease. European Heart Journal. 2022;43(7):561–632.
3. Bonow RO, et al. Valvular Heart Disease. In: Zipes DP, et al. Braunwald’s Heart Disease: A Textbook of Cardiovascular Medicine. 11th ed. Philadelphia: Elsevier; 2019. p. 1463–1532.
4. Perloff JK. The Clinical Recognition of Congenital Heart Disease. 6th ed. Philadelphia: Elsevier; 2012. p. 345–367.
5. Silversides CK, et al. Congenital pulmonary valve stenosis in adults: diagnosis and long-term follow-up. Canadian Journal of Cardiology. 2019;35(10):1294–1301.
6. Hoffman JIE, Kaplan S. The incidence of congenital heart disease. Journal of the American College of Cardiology. 2002;39(12):1890–900.
7. Mohamed S, et al. Pulmonary stenosis: diagnosis and management strategies. Heart. 2017;103(13):1042–1049.
8. Mullins CE. Cardiac Catheterization in Congenital Heart Disease. Malden: Blackwell Futura; 2006. p. 451–469.
9. Klabunde RE. Cardiovascular Physiology Concepts. 2nd ed. Philadelphia: Lippincott Williams & Wilkins; 2011. p. 191–202.
10. Morray BH, et al. Long-term outcomes after balloon valvuloplasty for congenital pulmonary valve stenosis. Journal of the American College of Cardiology. 2013;62(5):416–422.