Pulmonary Stenosis

Overview

Anatomy

Pulmonary (or pulmonic) valve:

• Semilunar valve between the right ventricle (RV) and pulmonary artery (PA)
• Consists of 3 cusps: anterior, left, and right
• Opens during systole as the RV pressure exceeds the pulmonary trunk pressure
• Closes during diastole as the RV pressure drops (S2), preventing retrograde flow from the pulmonary trunk

Definition and Epidemiology

Definition

Pulmonary stenosis is the narrowing of the pulmonary valve causing:

• An increased pressure gradient across the valve
• An obstruction to the flow from the RV to the PA

• Affects 7% of children with congenital heart defects
• Women > men
• Mild PS: good prognosis, with no difference from unaffected population
• Severe PS: 
  • Without treatment, advances to RV outflow obstruction
  • Intervention required by majority of affected patients within 10 years of diagnosis

Etiology and Classification

Etiology

• Cases are often congenital:
  • Isolated valvular PS: 
    • 10% of congenital heart disease
    • Valve is typically dome shaped.
  • Other congenital forms:
    • As part of Noonan syndrome: 
      • 50% of cases are associated with the PTPN1 gene mutation.
      • Usually with dysplastic valves
    • Tetralogy of Fallot (TOF):
      • Pulmonary valve stenosis 
      • Overriding aorta
      • RVH
      • Ventricular septal defect (VSD)
    • Congenital rubella syndrome
• Acquired PS:
  • Carcinoid syndrome
  • Rheumatic heart disease (rarely involves PS)
  • Previous cardiothoracic surgeries

Types of stenosis

• Valvular PS: 
  • Narrowed or thickened valve
  • Most common type
  • Associated with TOF, congenital rubella syndrome, Noonan syndrome, acquired PS from carcinoid syndrome
• Subvalvular infundibular PS:
  • Fibromuscular narrowing of the infundibular region, with normal valve
  • Rare
  • Can be found with other congenital lesions (TOF, VSD)
• Supravalvular (or peripheral) PS: 
  • Narrowing of the main PA or its branches, up to the periphery
  • Murmurs heard over the lungs
  • Mild form: nonpathologic, with murmur resolving by 6 months of age
  • Associated with congenital rubella syndrome or other anomalies (TOF, patent ductus arteriosus, VSD)

Pathophysiology and Clinical Presentation

Pathophysiology

• PS causes sustained outflow tract obstruction, which increases right ventricular afterload. 
• RV is less adaptive than the left ventricle, with early rises in pressures; so, with lower systolic pressures, RVH occurs.
• Right atrial (RA) pressure increases as a result of elevated RV pressure.
• Late in the disease: persistently increased RV strain → RV dysfunction occurs → eventual RV failure
• Other complications: arrhythmia, infective endocarditis

Symptoms

• Commonly asymptomatic during mild-to-moderate disease (majority of patients)
• Severe PS:
  • The more severe the obstruction is, the earlier it is detected.
  • Fatigue and exertional dyspnea 
  • Anginal chest pain from oxygen supply-demand mismatch
  • Syncope especially when accompanied by provoking factors (e.g., atrial fibrillation, infection)

Signs

• Prominent a wave in jugular venous pulse (strong atrial contraction)
• Heart sounds:
  • A high-pitched crescendo-decrescendo (diamond-shaped) systolic ejection murmur heard at the left upper sternal border (2nd intercostal space)
  • Murmur preceded by a pulmonary ejection click, which decreases with inspiration (the only right-sided sound that decreases with inspiration)
  • P2 delayed (wide S2 splitting)
  • Right-sided S3, S4 (RV failure)
• Left parasternal lift (from RVH) in severe PS
• Cyanosis in those with a right-to-left shunt (e.g., atrial septal defect)
• Very late in the course: peripheral edema, hepatomegaly, ascites

Diagnosis

• Transthoracic echocardiography (TTE) with Doppler: 
  • 2-dimensional (2D) and Doppler echocardiogram confirms the diagnosis.
  • Findings: 
    • Pulmonary valve thickening, doming of the valves
    • RVH, narrowed RV outflow tract
    • Post-stenotic dilation of the PA
    • Associated cardiac defects
    • Increased transvalvular gradient between the RV and the PA
  • Grading:
    • Mild PS: peak Doppler gradient < 30 mm Hg
    • Moderate PS: peak Doppler gradient of 30–50 mm Hg
    • Severe PS: peak Doppler gradient across the pulmonary valve of > 50 mm Hg
• Transesophageal echocardiography (TEE):
  • Use when assessing for infective endocarditis.
  • Not indicated for routine diagnosis of PS
• Electrocardiogram (ECG): 
  • Right axis deviation, RVH, right atrial enlargement
  • Right bundle branch block
• Chest X-ray: 
  • Frontal view: 
    • Prominent PA from post-stenotic dilation
    • Lifting of the cardiac apex off the diaphragm
    • Prominent right heart border from RA enlargement
  • Lateral view: filling of the retrosternal space by the enlarged RV
• Cardiac magnetic resonance imaging:
  • An option if TTE is suboptimal
  • Evaluates severity of the valve abnormalities and branch PA flow
  • Delineates anatomy of the PA and right heart
• Cardiac catheterization and pulmonary angiography:
  • Not necessary for the diagnosis of PS
  • Performed if clinical findings and echocardiographic findings are inconclusive
  • Provides information about concomitant congenital abnormalities

Management

• Monitoring:
  • Asymptomatic, with peak Doppler gradient < 30 mm Hg: physical examination, Doppler echocardiography, ECG every 5 years 
  • Asymptomatic, with peak Doppler gradient > 30 mm Hg: Doppler echocardiography every 2–5 years
• Diuretics: for symptoms of RV overload
• Percutaneous balloon valvotomy:
  • Symptomatic patients with a domed valve and a peak gradient > 50 mm Hg (or a mean gradient > 30 mm Hg)
  • Asymptomatic patients with a peak gradient > 60 mm Hg (or a mean gradient > 40 mm Hg)
• Surgical valvotomy for severe PS associated with:
  • Hypoplastic pulmonary annulus
  • Severe pulmonary regurgitation
  • Subvalvular PS
  • Most dysplastic valves
  • Severe tricuspid regurgitation
  • Surgical cardiac condition requiring operative intervention

Clinical Relevance

• TOF: cyanotic congenital heart disease characterized by the tetrad of RVH, an overriding aorta, pulmonary valve stenosis, and a ventricular septal defect. Surgically corrected TOF is a common cause for subsequent pulmonary regurgitation.
• Pulmonary atresia: a rare congenital cyanotic heart disease characterized by the failed formation of the pulmonary valve, leading to subsequent RV hypoplasia. Pulmonary atresia may occur as part of the most severe form of TOF (with VSD), where the entire RV outflow enters the aorta.
• Carcinoid syndrome: small, slow-growing neuroendocrine tumors. The tumors are associated with unregulated vasoactive hormone production, inducing the development of fibrous endocardial plaques and leading to pulmonary and tricuspid valve abnormalities.
• Rheumatic fever: a late complication of untreated streptococcal pharyngeal infection characterized by valvular abnormalities, most commonly of the left heart. While rare, the pulmonary valve can be affected concurrently with the mitral valve.