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Summary Table

Category	Details
Risk Factors	Congenital heart disease (most cases), Noonan syndrome, congenital rubella syndrome, carcinoid syndrome (acquired)
Etiology	Congenital malformation of the pulmonic valve (dome-shaped, thickened, fused commissures); less commonly subvalvular (infundibular) or supravalvular
Patient Presentation	Mild cases are asymptomatic and discovered incidentally via murmur; severe cases present with exertional dyspnea, fatigue, syncope, or signs of right heart failure
Classic Physical Exam	Crescendo-decrescendo systolic ejection murmur loudest at the left upper sternal border (pulmonic area), wide splitting of S2, systolic ejection click that decreases with inspiration
Key Diagnostic Results	Echocardiography showing thickened/domed pulmonic valve with restricted opening, elevated transvalvular pressure gradient; RV hypertrophy on ECG (right axis deviation, tall R in V1)
Management	Mild: observation. Moderate-to-severe (peak gradient >60 mmHg or mean >40 mmHg): percutaneous balloon valvuloplasty is the treatment of choice. Surgical valvotomy reserved for dysplastic valves
Keywords	"Ejection click that decreases with inspiration," "wide split S2," "systolic murmur at pulmonic area," "Noonan syndrome with murmur," "dome-shaped pulmonic valve"

1. Pathophysiology

Pulmonary stenosis refers to obstruction of right ventricular outflow at or near the pulmonic valve. The overwhelming majority of cases are congenital in origin, with the valve leaflets being thickened, fused at the commissures, and forming a dome-shaped structure that restricts opening during systole. This creates a fixed obstruction that the right ventricle must pump against.

Because the RV faces a chronically elevated afterload, it undergoes concentric hypertrophy as a compensatory response. In mild-to-moderate disease, this hypertrophy is sufficient to maintain cardiac output at rest, which is why most patients remain asymptomatic for years. The murmur is often discovered incidentally during a routine physical examination.

As the stenosis progresses or when the RV can no longer compensate, right ventricular failure develops. The failing RV cannot adequately fill the pulmonary vasculature, leading to decreased pulmonary blood flow and therefore reduced left-sided preload. This explains the exertional dyspnea and fatigue. Simultaneously, elevated RV end-diastolic pressure transmits backward into the right atrium and systemic venous system, producing jugular venous distension, hepatomegaly, peripheral edema, and a prominent "a" wave on JVP tracings (reflecting the atrium contracting against a stiff, hypertrophied RV).

The wide splitting of S2 is a direct hemodynamic consequence: the stenotic valve delays RV ejection, so the pulmonic valve closes later than normal. The more severe the stenosis, the later P2 occurs. In critical stenosis, P2 may become inaudible entirely because the valve is so rigid it no longer produces an audible closure sound.

The ejection click in pulmonary stenosis has a unique behavior compared to aortic stenosis. It decreases with inspiration. During inspiration, increased venous return to the right heart partially opens the domed pulmonic valve before systole begins, so when the RV contracts, there is less abrupt tensing of the valve and thus a softer or absent click. This is the only right-sided auscultatory finding that decreases with inspiration, making it a classic exam discriminator.

Acquired causes are far less common. Carcinoid syndrome produces serotonin and other vasoactive substances that cause fibrous plaque deposition on right-sided valve endocardium (because the lung metabolizes serotonin before it reaches the left heart). This leads to pulmonic stenosis and tricuspid regurgitation.

2. Classification and Clinical Manifestation

Classification by Anatomy

Type	Location	Key Features
Valvular (most common, ~90%)	At the pulmonic valve	Dome-shaped thickened valve with fused commissures; associated with ejection click
Subvalvular (Infundibular)	Below the valve in the RV outflow tract	Muscular or fibrous obstruction; often accompanies Tetralogy of Fallot; no ejection click
Supravalvular	Above the valve in the pulmonary artery or branches	Associated with congenital rubella, Williams syndrome (rarely), Alagille syndrome; no ejection click

Classification by Severity (Doppler Echocardiography)

Severity	Peak Gradient	Mean Gradient	Clinical Manifestation
Mild	<36 mmHg	<15 mmHg	Asymptomatic; soft, short systolic murmur; normal S2 splitting; prominent ejection click
Moderate	36-64 mmHg	15-40 mmHg	Exertional dyspnea, mild fatigue; longer and louder murmur; wider S2 split; click may diminish
Severe	>64 mmHg	>40 mmHg	Dyspnea, chest pain, syncope, right heart failure; murmur peaks late in systole; P2 diminished or absent; RV heave palpable
Critical (neonates)	Near-atretic valve	Duct-dependent	Cyanosis at birth, duct-dependent pulmonary blood flow; requires urgent intervention

Syndrome Associations

Syndrome	Valve Morphology	Distinguishing Feature
Noonan Syndrome	Dysplastic valve (thickened, myxomatous, immobile leaflets without commissural fusion)	Short stature, hypertelorism, webbed neck, pectus excavatum, cryptorchidism
Congenital Rubella	Peripheral/supravalvular branch stenosis	Cataracts, sensorineural deafness, PDA
Carcinoid Syndrome	Fibrotic thickening and retraction of valve leaflets	Flushing, diarrhea, wheezing, elevated 5-HIAA; typically causes combined PS and tricuspid regurgitation

3. Diagnostic Workup

Test	Role	Key Findings
Transthoracic Echocardiography (TTE)	Best initial test AND primary diagnostic tool	Thickened/domed valve, restricted systolic opening, post-stenotic PA dilatation; Doppler measures peak and mean transvalvular gradient
ECG	Screening/supportive	Right axis deviation, RV hypertrophy (tall R wave in V1, right atrial enlargement with peaked P waves in lead II)
Chest X-ray	Supportive	Post-stenotic dilatation of the main pulmonary artery (prominent PA segment), decreased pulmonary vascular markings in severe disease
Cardiac Catheterization	Gold standard for direct pressure measurement; also therapeutic	Direct measurement of RV-to-PA pressure gradient; simultaneous balloon valvuloplasty if intervention indicated

Echocardiography is the cornerstone of evaluation. It confirms the diagnosis, defines the anatomy (valvular vs. subvalvular vs. supravalvular), and quantifies severity through Doppler-derived pressure gradients. A peak instantaneous gradient above 64 mmHg or a mean gradient above 40 mmHg indicates severe stenosis requiring intervention. TTE also assesses RV size and function, the degree of tricuspid regurgitation (which reflects RV pressure overload), and whether the interatrial septum is intact or has a PFO/ASD that could permit right-to-left shunting.

ECG is not diagnostic on its own but provides supporting evidence of chronicity. In mild PS, the ECG may be entirely normal. As severity increases, you expect to see right axis deviation and RV hypertrophy pattern (dominant R wave in V1, deep S wave in V5-V6). Right atrial enlargement manifests as peaked P waves (P pulmonale) in the inferior leads.

Chest X-ray classically shows post-stenotic dilatation of the main pulmonary artery. This occurs because the high-velocity jet through the stenotic valve creates turbulence that dilates the PA segment just beyond the valve. The heart size may be normal in compensated disease or enlarged if RV failure has developed. Notably, post-stenotic dilatation is seen with valvular PS but typically not with subvalvular or supravalvular stenosis (because the jet hits a different anatomical segment).

Cardiac catheterization is reserved for cases where intervention is planned or when noninvasive data is inconclusive. It provides direct measurement of the pressure gradient between the RV and pulmonary artery and is performed simultaneously with balloon valvuloplasty when treatment is indicated.

4. Management and Treatment

Clinical Scenario	Management	Details
Asymptomatic, mild PS (peak gradient <36 mmHg)	Observation	Clinical follow-up with serial echocardiography every 3-5 years
Asymptomatic, moderate PS (peak gradient 36-64 mmHg)	Close surveillance	Echocardiography every 1-2 years; intervene if gradient progresses or symptoms develop
Symptomatic PS or severe PS (peak gradient >60 mmHg by catheterization, or >64 mmHg by Doppler)	Percutaneous balloon valvuloplasty	Treatment of choice for typical valvular PS with domed morphology
Dysplastic valve (e.g., Noonan syndrome)	Surgical valvotomy or valve replacement	Balloon valvuloplasty has poor results in dysplastic valves because the obstruction is from thickened leaflet tissue, not fused commissures
Subvalvular (infundibular) PS	Surgical resection of obstructing muscle/fibrous tissue	Balloon is ineffective for muscular obstruction
Critical PS in neonates	Prostaglandin E1 to maintain PDA + urgent balloon valvuloplasty	Duct-dependent pulmonary circulation; $PGE_1$ keeps the ductus arteriosus open to provide pulmonary blood flow until intervention
Carcinoid-related PS	Somatostatin analogs (octreotide) for carcinoid control + surgical valve replacement if severe	Medical management of the underlying carcinoid; valve replacement when hemodynamically indicated

Percutaneous balloon valvuloplasty is the definitive treatment for typical congenital valvular PS. The procedure involves threading a balloon catheter across the stenotic valve and inflating it to split the fused commissures. Success rates exceed 90%, with low complication rates and durable long-term results. The procedure is indicated when the peak catheterization gradient exceeds 60 mmHg (or Doppler peak gradient >64 mmHg), or at lower gradients if the patient is symptomatic.

A critical distinction for exam purposes: balloon valvuloplasty works well for domed valves with fused commissures but is ineffective for dysplastic valves. In Noonan syndrome, the pulmonic valve leaflets are thickened, myxomatous, and immobile, without true commissural fusion. Inflating a balloon across such a valve does not relieve obstruction because there are no commissures to split. These patients require surgical valvotomy or valve replacement.

For neonatal critical PS, the clinical picture is a cyanotic newborn with duct-dependent pulmonary blood flow. The immediate stabilization step is prostaglandin E1 infusion to prevent ductal closure, followed by urgent balloon valvuloplasty. This is analogous to any duct-dependent right-sided lesion (e.g., pulmonary atresia, critical PS, severe Tetralogy of Fallot in neonates).

After successful balloon valvuloplasty, patients generally have excellent long-term outcomes. Follow-up echocardiography monitors for residual stenosis and the development of pulmonic regurgitation (the most common post-procedure sequela, usually mild and well tolerated). Endocarditis prophylaxis is not routinely recommended for isolated PS after successful treatment, unless there is a prosthetic valve or prior endocarditis history.

5. Differential Diagnosis and Distractors

Differential Diagnosis	Why It Is Similar	Key Discriminator
Aortic Stenosis	Both produce a crescendo-decrescendo systolic ejection murmur with an ejection click	Aortic stenosis murmur is loudest at the right upper sternal border and radiates to the carotids; its ejection click does not change with respiration. PS murmur is at the left upper sternal border and the click decreases with inspiration
Atrial Septal Defect (ASD)	Both cause a systolic murmur at the pulmonic area and wide splitting of S2	ASD produces fixed splitting of S2 (does not vary with respiration); PS produces wide but variable splitting. ASD murmur is from increased flow, not obstruction
Tetralogy of Fallot	Both involve RV outflow obstruction (infundibular PS is a component of TOF)	TOF presents with cyanosis, right-to-left shunt through VSD, and a boot-shaped heart on CXR. Isolated PS has no VSD and is typically acyanotic (unless critical neonatal PS with PFO shunting)
Innocent (Flow) Murmur	Soft systolic ejection murmur in an asymptomatic child	Innocent murmurs have no click, no thrill, normal S2 splitting, and a normal echocardiogram. The presence of an ejection click or abnormal S2 rules out an innocent murmur
Hypertrophic Cardiomyopathy (HCM)	Systolic murmur that can vary with maneuvers	HCM murmur increases with Valsalva and standing (reduced preload); PS murmur does not. HCM is a left-sided outflow obstruction with different location and character
Pulmonary Artery Hypertension	RV hypertrophy, loud P2, JVD	In PAH, P2 is loud (not diminished); there is no ejection click and no stenotic murmur. The pathology is in the pulmonary vasculature, not the valve

6. Traps and High-Yield Pearls

The single most tested concept in pulmonary stenosis is the behavior of the ejection click. Students commonly apply the rule that all right-sided heart sounds increase with inspiration and mark the wrong answer. The ejection click of PS is the notable exception: it decreases with inspiration because the increased venous return pre-opens the domed valve, eliminating the abrupt snap. If a vignette describes a systolic click at the left upper sternal border that becomes softer when the patient takes a deep breath, that is pulmonary stenosis until proven otherwise.

The second common trap involves confusing PS with ASD. Both can present as an asymptomatic murmur at the pulmonic area with widened S2 splitting. The distinguishing feature is whether the split is fixed (ASD) or variable (PS). Test-writers rely on this distinction heavily, and a single word in the stem ("fixed" vs. "wide") changes the correct answer entirely.

A third pitfall is the management of dysplastic valves. Students who memorize "balloon valvuloplasty for pulmonic stenosis" without nuance will select the wrong treatment for a patient with Noonan syndrome features. When the vignette describes short stature, a webbed neck, and a dysplastic pulmonic valve on echocardiography, the correct answer shifts to surgical intervention.

Finally, for neonatal critical PS, the tested competency is recognizing a duct-dependent lesion. Any cyanotic neonate who worsens as the ductus closes should trigger the reflex to start prostaglandin E1 infusion as the immediate stabilization step, before any definitive repair.

The core skill being assessed across all PS questions is the ability to integrate auscultatory findings (murmur location, click behavior, S2 splitting pattern) with hemodynamic reasoning to arrive at the correct diagnosis and appropriate next step.

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