Pulmonic Valve Disorders

Introduction

Among the four cardiac valves, the pulmonic valve is often the least discussed in clinical practice. This valve, located between the right ventricle (RV) and the pulmonary artery, ensures unidirectional blood flow during ventricular systole, propelling deoxygenated blood into the lungs for gas exchange. Compared to left-sided valvular lesions such as aortic or mitral disease, pulmonic valve disorders are rare. However, their importance cannot be overlooked, as these conditions can significantly affect hemodynamics, right ventricular function, and long-term outcomes, particularly in congenital heart disease.

Pulmonic valve disease encompasses two broad categories:

1. Pulmonic Stenosis (PS): Obstruction of blood flow from the RV to the pulmonary artery due to valvular narrowing.
2. Pulmonic Regurgitation (PR): Backward flow of blood into the RV during diastole due to valve incompetence.

Both conditions may be congenital or acquired, but congenital etiologies dominate the clinical landscape. In this post, we will examine pulmonic valve disorders in detail—focusing on stenosis, regurgitation, congenital vs acquired causes, clinical relevance, and diagnostic approaches.

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Pulmonic Stenosis

Definition and Overview

Pulmonic stenosis (PS) refers to narrowing of the pulmonic valve orifice, which imposes a pressure load on the right ventricle. It accounts for 8–12% of congenital heart defects and is most often detected in childhood or adolescence. In adults, isolated pulmonic stenosis is relatively uncommon unless it has persisted since birth.

Types of Pulmonic Stenosis

• Valvular PS: The most common form, caused by dysplastic, fused, or thickened valve cusps.
• Subvalvular (infundibular) PS: Narrowing below the valve, often due to muscular hypertrophy of the RV outflow tract.
• Supravalvular PS: Narrowing above the valve, typically involving the main pulmonary artery.

Hemodynamics

In PS, the RV must generate higher systolic pressure to overcome the obstruction. This leads to right ventricular hypertrophy (RVH) and, if severe, eventual RV failure. The degree of stenosis is classified by the pressure gradient across the pulmonic valve:

• Mild: Gradient < 36 mmHg
• Moderate: 36–64 mmHg
• Severe: > 64 mmHg

Clinical Features

• Symptoms:
  • Often asymptomatic in mild cases.
  • Dyspnea on exertion, fatigue, and chest discomfort in moderate to severe cases.
  • Syncope or sudden cardiac death (rare, in severe cases).
• Physical Exam Findings:
  • Systolic ejection murmur best heard at the left upper sternal border.
  • Ejection click that decreases with inspiration (unlike aortic stenosis).
  • A delayed and diminished P2 (pulmonic component of S2).
  • Jugular venous distension (in advanced disease).

Diagnosis

• Echocardiography (Echo): First-line modality. Doppler estimates pressure gradient across the valve.
• ECG: Shows RV hypertrophy or right axis deviation.
• Chest X-ray: May show post-stenotic dilatation of the pulmonary artery.
• Cardiac MRI/CT: For anatomical delineation, especially pre-intervention.

Management

• Mild PS: No treatment, regular monitoring.
• Moderate to severe PS: Balloon valvuloplasty is the treatment of choice, particularly for valvular PS.
• Surgical repair or valve replacement: Indicated if balloon valvuloplasty is ineffective or in non-valvular forms.

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Pulmonic Regurgitation

Definition and Overview

Pulmonic regurgitation (PR) occurs when the pulmonic valve fails to close properly during diastole, allowing blood to leak back into the RV. Mild PR is physiologic and commonly detected in normal individuals via Doppler echocardiography. Clinically significant PR is less frequent but has important long-term implications.

Causes

Congenital Causes

• Tetralogy of Fallot (TOF) repair: Surgical interventions often lead to chronic PR due to removal of the pulmonary valve or use of conduits.
• Congenital absence or malformation of the pulmonic valve.

Acquired Causes

• Pulmonary hypertension: Leads to dilation of the pulmonary annulus, causing functional PR.
• Infective endocarditis: Rare, but can damage the pulmonic valve.
• Carcinoid heart disease: Affects right-sided valves, including pulmonic.
• Iatrogenic causes: Following balloon valvuloplasty for PS.

Hemodynamics

PR causes volume overload of the RV, leading to dilatation, dysfunction, and eventually right-sided heart failure. The severity of PR is determined by regurgitant volume and annular dilation.

Clinical Features

• Symptoms: Often absent until RV dysfunction develops. Patients may experience fatigue, dyspnea, palpitations, and peripheral edema.
• Physical Exam Findings:
  • High-pitched, decrescendo early diastolic murmur at the left upper sternal border (Graham Steell murmur, particularly in pulmonary hypertension).
  • Prominent jugular venous pulsations.
  • RV lift or heave on palpation.

Diagnosis

• Echocardiography: Gold standard for grading PR severity and assessing RV size/function.
• Cardiac MRI: Preferred in repaired congenital heart disease for quantifying regurgitant fraction and RV volumes.
• ECG: May show right atrial enlargement, RV hypertrophy, or arrhythmias.

Management

• Mild/Moderate PR: No specific treatment; monitor with serial imaging.
• Severe PR with RV dilation or dysfunction: Pulmonic valve replacement (surgical or transcatheter) is recommended.
• Secondary PR due to pulmonary hypertension: Treat underlying cause.

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Congenital vs. Acquired Pulmonic Valve Disorders

Congenital Disorders

• Stenosis: Predominantly congenital, often isolated or associated with syndromes (e.g., Noonan syndrome).
• Regurgitation: Frequently occurs after surgical repair of congenital defects (e.g., TOF).

Acquired Disorders

• Much less common compared to congenital.
• Causes include pulmonary hypertension, infective endocarditis, rheumatic disease (rare), or iatrogenic injury.

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Clinical Relevance

Although pulmonic valve disorders are rare compared to mitral or aortic valve disease, they hold significant clinical importance in:

1. Congenital Heart Disease Survivors: With advances in pediatric cardiology, more patients with repaired TOF or congenital pulmonic stenosis survive into adulthood. Chronic PR and RV dysfunction are major long-term issues in this population.
2. Pulmonary Hypertension: Functional PR serves as a marker of disease severity and right ventricular compromise.
3. Differentiation from Other Murmurs: Pulmonic murmurs must be distinguished from aortic and tricuspid murmurs for accurate diagnosis.

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Diagnostic Features

A systematic approach is essential for accurate diagnosis:

1. History and Clinical Examination: Focus on exertional symptoms, right heart failure signs, and murmur characteristics.
2. Electrocardiography: Helps assess RV strain or hypertrophy.
3. Imaging Modalities:
   • Echocardiography: First-line tool.
   • MRI: Superior for RV functional assessment and quantification of regurgitation.
   • CT: Useful in complex congenital anatomy or when MRI is contraindicated.
4. Cardiac Catheterization: Rarely needed, reserved for intervention planning.

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Prognosis

• Mild PS/PR: Excellent prognosis with near-normal life expectancy.
• Severe untreated PS: Leads to RV failure, arrhythmias, and reduced survival.
• Chronic severe PR: Progressive RV dilatation and dysfunction, increasing risk of sudden cardiac death in congenital heart disease survivors.
• Interventional outcomes: Balloon valvuloplasty and valve replacements significantly improve prognosis and quality of life.