Acyanotic Congenital Heart Disease: Obstructive Lesions

Pulmonary Valve Stenosis

Definition and Pathophysiology

Pulmonary valve stenosis (PS) is a congenital heart defect characterized by narrowing of the pulmonary valve, which obstructs blood flow from the right ventricle to the pulmonary artery. The stenosis can occur at valvular, subvalvular, or supravalvular levels, with valvular being the most common.

In PS, the valve leaflets are often thickened, fused, or dysplastic. This narrowing creates resistance to right ventricular outflow, leading to increased right ventricular pressure and hypertrophy. The severity of stenosis determines the degree of obstruction and subsequent right ventricular adaptation.

Epidemiology

PS accounts for 8-12% of all congenital heart defects, making it one of the most common. It occurs in approximately 1 in 2000 live births and can be associated with genetic syndromes such as Noonan syndrome.

Clinical Presentation

The clinical presentation varies based on the severity of stenosis:

  • Mild PS: Often asymptomatic and may be detected incidentally during routine examinations.
  • Moderate PS: Patients may experience fatigue, dyspnea on exertion, or chest pain.
  • Severe PS: Symptoms include marked exercise intolerance, syncope, and right-sided heart failure.
  • Critical PS in neonates: Can present with cyanosis, tachypnea, and signs of right heart failure.

Physical Examination Findings

  • Systolic ejection murmur, best heard at the left upper sternal border
  • Ejection click may be present, decreasing with inspiration
  • Right ventricular heave in moderate to severe cases
  • Jugular venous distention and hepatomegaly in severe cases with right heart failure

Diagnostic Approach

  1. Electrocardiogram (ECG):
    • Right axis deviation
    • Right ventricular hypertrophy
    • Right atrial enlargement in severe cases
  2. Chest X-ray:
    • Normal heart size in mild cases
    • Enlarged right ventricle and main pulmonary artery in moderate to severe cases
    • Decreased pulmonary vascular markings
  3. Echocardiography:
    • Gold standard for diagnosis
    • Assesses valve morphology and motion
    • Measures pressure gradient across the valve
    • Evaluates right ventricular size, function, and hypertrophy
  4. Cardiac Catheterization:
    • Not routinely needed for diagnosis
    • May be performed for intervention (balloon valvuloplasty)
    • Provides accurate measurement of pressure gradients

Management

Treatment depends on the severity of stenosis and patient's age:

  • Mild PS (gradient <30 mmHg): Regular follow-up, no intervention needed
  • Moderate PS (gradient 30-50 mmHg): Balloon valvuloplasty if symptomatic
  • Severe PS (gradient >50 mmHg): Balloon valvuloplasty or surgical valvotomy
  • Critical PS in neonates: Urgent intervention required, often with prostaglandin E1 to maintain ductal patency before definitive treatment

Balloon Valvuloplasty

This is the preferred treatment for valvular PS. A balloon catheter is inflated across the stenotic valve, causing commissural splitting and valve expansion. Success rates are high, with low complication rates.

Surgical Intervention

Surgery is reserved for cases where balloon valvuloplasty is contraindicated or unsuccessful. Options include open valvotomy, valve repair, or valve replacement.

Prognosis and Follow-up

Prognosis is generally excellent with timely intervention. Most patients lead normal lives post-treatment. However, long-term follow-up is necessary to monitor for:

  • Restenosis
  • Development of pulmonary regurgitation
  • Right ventricular function
  • Exercise capacity
  • Arrhythmias

Endocarditis prophylaxis is not routinely recommended except in high-risk cases.

Special Considerations

  • Pregnancy: Generally well-tolerated in mild to moderate PS. Severe PS should be treated before pregnancy.
  • Exercise: No restrictions for mild PS. Moderate to severe PS may require activity modification.
  • Associated lesions: PS can occur in conjunction with other cardiac defects, necessitating comprehensive evaluation.

Aortic Stenosis

Definition and Pathophysiology

Aortic stenosis (AS) is a congenital heart defect characterized by narrowing of the aortic valve, obstructing blood flow from the left ventricle to the aorta. This narrowing can occur at three levels:

  • Valvular: Most common, involving the valve leaflets
  • Subvalvular: Obstruction below the valve
  • Supravalvular: Narrowing of the ascending aorta

The stenotic aortic valve creates resistance to left ventricular outflow, leading to increased left ventricular pressure and hypertrophy. Over time, this can result in left ventricular diastolic dysfunction and eventually systolic dysfunction if left untreated.

Epidemiology

Congenital AS accounts for 3-6% of all congenital heart defects. It's more common in males (male-to-female ratio of 4:1). Bicuspid aortic valve, the most common cause of congenital AS, occurs in 1-2% of the general population.

Clinical Presentation

The presentation varies based on the severity and age of onset:

  • Neonates with critical AS: Cardiogenic shock, poor feeding, tachypnea
  • Infants: Failure to thrive, respiratory distress
  • Children: Often asymptomatic, may have decreased exercise tolerance
  • Adolescents/Adults: Classic triad of angina, syncope, and dyspnea

Physical Examination Findings

  • Harsh systolic ejection murmur, best heard at the right upper sternal border, radiating to the carotids
  • Ejection click may be present (absent in severe calcific stenosis)
  • Narrow pulse pressure with pulsus parvus et tardus (delayed and weak peripheral pulses)
  • Left ventricular heave
  • In severe cases: Signs of heart failure (rales, edema, hepatomegaly)

Diagnostic Approach

  1. Electrocardiogram (ECG):
    • Left ventricular hypertrophy
    • Left atrial enlargement
    • ST-T wave changes indicating strain
  2. Chest X-ray:
    • Normal heart size in compensated AS
    • Left ventricular enlargement in advanced cases
    • Post-stenotic dilation of the ascending aorta
    • Calcification of the aortic valve (in older patients)
  3. Echocardiography:
    • Gold standard for diagnosis
    • Assesses valve morphology and calcification
    • Measures aortic valve area and pressure gradient
    • Evaluates left ventricular size, function, and hypertrophy
    • Assesses for associated lesions (e.g., coarctation, mitral valve abnormalities)
  4. Cardiac Catheterization:
    • Not routinely needed for diagnosis
    • May be performed pre-operatively in adults
    • Provides accurate measurement of pressure gradients and cardiac output
  5. Exercise Testing:
    • Useful in assessing exercise capacity and symptoms in asymptomatic patients
    • Can unmask symptoms and provide prognostic information

Management

Treatment depends on the severity of stenosis, patient age, and symptoms:

  • Mild AS: Regular follow-up, no intervention needed
  • Moderate AS: Close monitoring, intervention if becoming symptomatic
  • Severe AS: Intervention recommended, even if asymptomatic
  • Critical AS in neonates: Urgent intervention required

Balloon Valvuloplasty

Often used as initial treatment in children and as a bridge to surgery in adults. A balloon catheter is inflated across the stenotic valve, causing commissural splitting and valve expansion.

Surgical Intervention

Options include:

  • Surgical valvotomy: For non-calcified valves in younger patients
  • Ross procedure: Pulmonary autograft replacement of the aortic valve (for children and young adults)
  • Valve replacement: Mechanical or bioprosthetic valves (more common in adults)

Transcatheter Aortic Valve Replacement (TAVR)

Increasingly used in adult patients with calcific AS, especially those at high surgical risk.

Prognosis and Follow-up

Prognosis depends on the severity of AS and timing of intervention:

  • Excellent outcomes with early intervention in children
  • Adults with severe symptomatic AS have poor prognosis without intervention
  • Long-term follow-up is necessary to monitor for:
    • Progression of stenosis
    • Left ventricular function
    • Development of symptoms
    • Complications of prosthetic valves (if present)

Special Considerations

  • Pregnancy: High-risk in severe AS. Consider intervention before pregnancy if severe.
  • Exercise: Restricted in moderate to severe AS. Competitive sports are contraindicated in symptomatic patients.
  • Endocarditis prophylaxis: Recommended for prosthetic valves and in the first 6 months after valve intervention.
  • Associated lesions: AS can be part of complex congenital heart defects (e.g., Shone's complex).

Coarctation of the Aorta

Definition and Pathophysiology

Coarctation of the aorta (CoA) is a congenital narrowing of the aorta, typically occurring just distal to the left subclavian artery. It can be classified as:

  • Preductal (infant type): Proximal to the ductus arteriosus
  • Postductal (adult type): Distal to the ductus arteriosus

The narrowing creates a pressure gradient between the upper and lower body, leading to hypertension in the upper body and relative hypotension in the lower body. This increased afterload causes left ventricular hypertrophy and potential heart failure.

Epidemiology

CoA accounts for 5-8% of all congenital heart defects. It's more common in males (male-to-female ratio of 1.5-2:1). CoA is associated with other cardiac defects, particularly bicuspid aortic valve (in up to 50% of cases) and ventricular septal defect.

Clinical Presentation

The presentation varies based on the severity and age of presentation:

  • Neonates: May present with cardiogenic shock when the ductus arteriosus closes
  • Infants: Congestive heart failure, poor feeding, failure to thrive
  • Children/Adults: Often asymptomatic, may have hypertension, headaches, leg claudication

Physical Examination Findings

  • Blood pressure difference between upper and lower extremities (>20 mmHg significant)
  • Weak or delayed femoral pulses compared to brachial pulses
  • Systolic murmur best heard in the left interscapular area
  • Continuous murmur due to collateral vessels (in long-standing cases)
  • Palpable thoracic aorta pulsation

Diagnostic Approach

  1. Electrocardiogram (ECG):
    • Left ventricular hypertrophy
    • Possible right ventricular hypertrophy in infants
  2. Chest X-ray:
    • "Figure 3" sign (indentation of aorta at coarctation site)
    • Rib notching (in older children/adults due to collateral vessels)
    • Cardiomegaly in infants with heart failure
  3. Echocardiography:
    • Visualization of the coarctation
    • Measurement of pressure gradient across the narrowing
    • Assessment of left ventricular size and function
    • Evaluation for associated cardiac defects
  4. CT/MRI Angiography:
    • Detailed imaging of the aorta and collateral vessels
    • Particularly useful in planning interventions
  5. Cardiac Catheterization:
    • Accurate measurement of pressure gradients
    • Assessment of collateral flow
    • Can be combined with intervention (balloon angioplasty/stenting)

Management

Treatment depends on the age at presentation and severity of coarctation:

Medical Management

  • Prostaglandin E1 in neonates to maintain ductal patency
  • Antihypertensive therapy as needed

Surgical Repair

  • End-to-end anastomosis: Resection of the narrowed segment and direct anastomosis
  • Subclavian flap aortoplasty: Using left subclavian artery to patch the coarctation
  • Patch aortoplasty: Synthetic patch to enlarge the narrowed segment

Catheter-Based Interventions

  • Balloon angioplasty: Often used as initial treatment in older children/adults
  • Stent placement: Provides better long-term results compared to balloon angioplasty alone

Prognosis and Follow-up

Prognosis is generally good with early intervention, but lifelong follow-up is necessary:

  • Monitor for recoarctation (10-20% of cases)
  • Ongoing risk of systemic hypertension
  • Surveillance for aneurysm formation at the repair site
  • Screening for associated cardiovascular abnormalities (e.g., bicuspid aortic valve, berry aneurysms)

Complications

  • Persistent hypertension
  • Premature coronary artery disease
  • Cerebrovascular disease
  • Aortic aneurysm or dissection
  • Endocarditis (rare)

Special Considerations

  • Pregnancy: High-risk in unrepaired or residual CoA. Consider intervention before pregnancy if significant.
  • Exercise: Restrictions based on the presence of residual obstruction or hypertension.
  • Endocarditis prophylaxis: Not routinely recommended except in the first 6 months after repair.

Congenital Mitral Stenosis

Definition and Pathophysiology

Congenital mitral stenosis (MS) is a rare heart defect characterized by narrowing of the mitral valve, obstructing blood flow from the left atrium to the left ventricle. It can occur in several forms:

  • Typical congenital MS: Thickened valve leaflets with shortened chordae tendineae
  • Parachute mitral valve: Single papillary muscle
  • Supravalvular mitral ring: Fibrous membrane above the mitral valve
  • Hypoplastic mitral valve: Underdeveloped valve and annulus

The stenotic mitral valve creates resistance to left atrial emptying, leading to increased left atrial pressure and eventual left atrial enlargement. This can result in pulmonary venous congestion and pulmonary hypertension over time.

Epidemiology

Congenital MS is rare, accounting for 0.6% of congenital heart defects. It's often associated with other left heart obstructive lesions, such as in Shone's complex (which includes coarctation of the aorta, subaortic stenosis, and aortic valve abnormalities).

Clinical Presentation

The presentation varies based on the severity of stenosis and associated lesions:

  • Neonates/Infants: Tachypnea, poor feeding, failure to thrive, recurrent respiratory infections
  • Children: Exercise intolerance, dyspnea, fatigue
  • Older children/Adults: May develop atrial fibrillation, hemoptysis

Physical Examination Findings

  • Diastolic rumble at the apex
  • Loud S1
  • Opening snap may be present
  • Signs of pulmonary hypertension in advanced cases (loud P2, right ventricular heave)

Diagnostic Approach

  1. Electrocardiogram (ECG):
    • Left atrial enlargement
    • Possible right ventricular hypertrophy in cases with pulmonary hypertension
  2. Chest X-ray:
    • Left atrial enlargement
    • Pulmonary venous congestion
    • Possible calcification of the mitral valve in older patients
  3. Echocardiography:
    • Gold standard for diagnosis
    • Assesses valve morphology and motion
    • Measures mitral valve area and gradient
    • Evaluates left atrial size and left ventricular function
    • Estimates pulmonary artery pressure
  4. Cardiac Catheterization:
    • Not routinely needed for diagnosis
    • May be performed to assess hemodynamics and pulmonary vascular resistance
    • Useful in planning surgical intervention
  5. CT/MRI:
    • Provides detailed anatomical information
    • Helpful in evaluating associated lesions

Management

Treatment depends on the severity of stenosis, associated lesions, and patient age:

Medical Management

  • Diuretics for symptom relief
  • Anticoagulation if atrial fibrillation develops
  • Management of pulmonary hypertension if present

Interventional Procedures

  • Balloon valvuloplasty: May be attempted in selected cases, but often less effective than in other valve lesions

Surgical Options

  • Commissurotomy: Splitting of fused commissures
  • Mitral valve repair: Various techniques depending on valve anatomy
  • Mitral valve replacement: Used when repair is not feasible

Prognosis and Follow-up

Prognosis varies depending on the severity of stenosis, associated lesions, and timing of intervention:

  • Early intervention is crucial to prevent irreversible pulmonary vascular changes
  • Regular follow-up is necessary to monitor:
    • Disease progression
    • Left atrial size and function
    • Development of pulmonary hypertension
    • Complications of interventions (e.g., prosthetic valve function)

Complications

  • Pulmonary hypertension
  • Atrial fibrillation
  • Thromboembolic events
  • Heart failure

Special Considerations

  • Pregnancy: High-risk in moderate to severe MS. Consider intervention before pregnancy if significant.
  • Exercise: Restrictions based on severity of stenosis and presence of pulmonary hypertension.
  • Endocarditis prophylaxis: Recommended for prosthetic valves and in the first 6 months after valve repair.

Pulmonary Venous Hypertension

Definition and Pathophysiology

Pulmonary venous hypertension (PVH) is a condition characterized by elevated pressure in the pulmonary veins, often secondary to left heart disease or, in congenital cases, due to obstructed pulmonary venous return. In the context of congenital heart disease, it can be caused by:

  • Total or partial anomalous pulmonary venous return
  • Cor triatriatum sinister
  • Congenital mitral stenosis
  • Left heart obstruction (e.g., hypoplastic left heart syndrome)

Increased left atrial pressure leads to elevated pulmonary venous pressure, causing pulmonary capillary congestion and interstitial edema. Over time, changes in the pulmonary vasculature can lead to pulmonary arterial hypertension.

Epidemiology

The prevalence of PVH in congenital heart disease varies depending on the underlying condition. It's more common in lesions that obstruct pulmonary venous drainage or increase left atrial pressure.

Clinical Presentation

Symptoms depend on the severity and underlying cause:

  • Infants: Tachypnea, poor feeding, failure to thrive, recurrent respiratory infections
  • Children/Adults: Dyspnea, orthopnea, fatigue, hemoptysis
  • In severe cases: Right heart failure symptoms (peripheral edema, ascites)

Physical Examination Findings

  • Tachypnea and increased work of breathing
  • Fine crackles on lung auscultation
  • Loud P2 in cases with pulmonary arterial hypertension
  • Right ventricular heave in advanced cases
  • Hepatomegaly and peripheral edema in right heart failure

Diagnostic Approach

  1. Electrocardiogram (ECG):
    • Left atrial enlargement
    • Possible right ventricular hypertrophy in advanced cases
  2. Chest X-ray:
    • Pulmonary venous congestion
    • Kerley B lines
    • Possible cardiomegaly
  3. Echocardiography:
    • Assesses left heart function and structure
    • Estimates pulmonary artery pressure
    • Evaluates for underlying structural abnormalities
  4. Cardiac Catheterization:
    • Gold standard for diagnosis
    • Measures pulmonary capillary wedge pressure (PCWP)
    • Assesses pulmonary vascular resistance
  5. CT/MRI Angiography:
    • Detailed imaging of pulmonary veins and cardiac structures
    • Particularly useful in anomalous pulmonary venous return

Management

Treatment focuses on addressing the underlying cause and managing symptoms:

Medical Management

  • Diuretics to reduce congestion
  • Supplemental oxygen as needed
  • Pulmonary vasodilators in cases with significant pulmonary arterial hypertension

Surgical/Interventional Management

  • Repair of anomalous pulmonary venous return
  • Resection of cor triatriatum membrane
  • Treatment of mitral valve disease or other left heart obstructions

Prognosis and Follow-up

Prognosis depends on the underlying cause and the degree of pulmonary vascular remodeling:

  • Early diagnosis and treatment of the primary lesion is crucial to prevent irreversible pulmonary vascular disease
  • Long-term follow-up is necessary to monitor for:
    • Progression of pulmonary hypertension
    • Right ventricular function
    • Recurrence of obstruction in repaired lesions

Complications

  • Progressive pulmonary arterial hypertension
  • Right heart failure
  • Arrhythmias
  • Hemoptysis

Special Considerations

  • Pregnancy: High-risk in patients with significant pulmonary hypertension
  • Altitude: Patients may experience worsening symptoms at high altitudes
  • Exercise: Restrictions based on severity of pulmonary hypertension and right ventricular function
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