Pulmonary Stenosis in Children

Also written as Pulmonary outflow tract obstruction.

Pulmonary stenosis is a congenital narrowing of the right ventricular outflow tract that limits blood flow to the lungs. It presents with a harsh systolic murmur and right‑ventricular strain. Management depends on severity and resource availability.

Definition and diagnosis

Pulmonary stenosis (PS) is a congenital narrowing of the pulmonary valve or right ventricular outflow tract that impedes systolic blood flow into the pulmonary artery.

• Echocardiography: Shows valve morphology, gradient across the stenosis, and right ventricular size – a peak gradient >40 mmHg indicates severe PS
• Chest X‑ray: May show right ventricular prominence and a small pulmonary vascular bed in severe cases
• ECG: Right‑axis deviation and RV hypertrophy; a prominent P wave (a‑wave) suggests severe obstruction

• Harsh systolic ejection murmur at left upper sternal border
• Right ventricular heave
• Prominent a‑wave in jugular pulse in severe cases

Severity and staging

Severity is graded by peak systolic gradient and right‑ventricular function.

• Mild: <30 mmHg, no RV hypertrophy
• Moderate: 30–50 mmHg, mild RV hypertrophy
• Severe: >50 mmHg, marked RV hypertrophy and possible RV failure

Causes, most likely first

PS is primarily a congenital defect, but infections and environmental factors can exacerbate or mimic it.

• Congenital: isolated PS, PS with VSD, PS with Tetralogy of Fallot
• Infectious: rheumatic fever can cause valvular damage leading to PS
• Environmental: maternal rubella, alcohol exposure, high altitude hypoxia

How it presents

Clinical features vary with severity and associated lesions.

• Harsh systolic murmur at left upper sternal border
• Poor feeding and failure to thrive in infants
• Exercise intolerance, tachypnoea in older children
• Syncope or fainting in severe cases

Investigations

Choose tests based on availability and clinical urgency.

• Echocardiography: Determines gradient, valve anatomy, and RV size – essential for staging
• Pulse oximetry: Shows oxygen saturation; <90 % suggests significant obstruction or shunt
• Chest X‑ray: Assesses cardiac silhouette and pulmonary vasculature
• ECG: Detects RV hypertrophy and arrhythmias
• Blood tests (CBC, CRP): Rule out infection or anemia that may worsen symptoms

Red flags and complications

Early recognition of life‑threatening features is critical.

• Severe RV failure – tachycardia, hypotension, cool extremities
• Acute decompensation after dehydration or infection
• Pulmonary hypertension secondary to chronic obstruction
• Arrhythmias such as supraventricular tachycardia

Management

Treatment is tailored to severity and resource setting.

• Prostaglandin E1 (if available): Maintains ductal patency in critical PS to improve pulmonary flow
• Beta‑blockers (e.g., propranolol): Reduce heart rate and improve diastolic filling in moderate PS
• Balloon valvuloplasty: First‑line for isolated PS when gradient >40 mmHg and anatomy suitable; performed by cardiology team
• Surgical patch repair or valve replacement: Reserved for severe PS not amenable to catheter intervention or with complex anatomy

• Supportive care: maintain hydration, avoid dehydration, treat infections promptly

Follow‑up and prevention

Regular monitoring and early intervention prevent complications.

• Annual echocardiogram for moderate to severe PS
• Vaccination against pneumococcus and influenza to reduce infection risk
• Counselling on avoiding high‑altitude exposure

Often confused with

Conditions that mimic PS symptoms or auscultatory findings.

• Aortic stenosis – harsh systolic murmur at right upper sternal border
• Tetralogy of Fallot – harsh PS murmur plus cyanosis and VSD murmur

Where results can mislead

Certain investigations may give false normals or misleading values in low‑resource settings.

• Pulse oximetry: May read normal if patient is at rest but drops during activity

• Echocardiography may underestimate gradient if Doppler angle is off

Questions an examiner may ask

• What is the most appropriate first investigation for a 6‑month‑old with a harsh systolic murmur at the left upper sternal border? — Echocardiography to assess gradient and anatomy.
• A child with PS presents with syncope during play. What is the most likely underlying mechanism? — Severe RV outflow obstruction leading to transient cerebral hypoperfusion.
• You have a 10‑year‑old with PS and a VSD. Which intervention is preferred if the PS gradient is 45 mmHg? — Balloon valvuloplasty before addressing the VSD.
• Why is a loud harsh murmur at the left upper sternal border characteristic of PS? — It reflects high‑velocity jet across a narrowed pulmonary valve.
• A patient with PS is admitted with dehydration. What is the immediate priority? — Rehydrate to prevent worsening RV failure.
• Which drug is contraindicated in PS due to risk of worsening obstruction? — Calcium channel blockers (e.g., verapamil) because they reduce RV contractility.
• How would you differentiate PS from aortic stenosis on auscultation? — PS murmur is left upper sternal border; aortic stenosis is right upper sternal border.
• What is the key echocardiographic sign of severe PS? — Peak systolic gradient >50 mmHg with RV hypertrophy.

When to seek help

• Severe tachycardia with hypotension
• Sudden cyanosis or fainting
• Signs of right‑ventricular failure (cool extremities, poor capillary refill)

Quick questions

Can pulmonary stenosis resolve on its own?

No, PS is a structural defect; mild cases may remain stable but do not improve spontaneously.

What is the role of prostaglandin in PS?

It keeps the ductus arteriosus open, allowing pulmonary blood flow in critically ill infants with severe PS.

Why avoid aspirin in PS?

Aspirin can increase bleeding risk and does not address the obstruction; it is not indicated unless there is a thrombotic complication.