Atrial Septal Defects: Clinical Case and Viva QnA

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Clinical Case of Atrial Septal Defect

A 4-year-old girl is brought to the pediatric cardiology clinic for evaluation of a heart murmur detected during a routine check-up. Her parents report that she occasionally gets tired during play but has no other significant symptoms. There is no history of cyanosis, chest pain, or syncope.

On examination:

  • Weight: 16 kg (50th percentile)
  • Height: 102 cm (50th percentile)
  • Vital signs: HR 100 bpm, RR 22/min, BP 95/60 mmHg
  • Cardiovascular: Fixed split S2, grade 2/6 systolic ejection murmur at left upper sternal border
  • No cyanosis or clubbing
  • Normal peripheral pulses

Investigations:

  • Chest X-ray: Mild cardiomegaly, increased pulmonary vascularity
  • ECG: Right axis deviation, incomplete right bundle branch block
  • Echocardiogram: 15 mm secundum atrial septal defect with left-to-right shunt, mild right ventricular dilation

Based on these findings, the patient is diagnosed with a secundum atrial septal defect. The cardiologist discusses management options with the family, including the potential need for surgical or catheter-based closure of the defect.

5 Varieties of Presentation of Atrial Septal Defects
  1. Asymptomatic Presentation:
    • Incidental finding of heart murmur during routine examination
    • No overt symptoms
    • Normal growth and development
  2. Symptomatic Presentation in Infancy:
    • Failure to thrive
    • Recurrent respiratory infections
    • Tachypnea and increased work of breathing
    • Signs of congestive heart failure in large defects
  3. Exercise Intolerance in Older Children:
    • Reduced exercise capacity
    • Fatigue with physical activity
    • Shortness of breath on exertion
    • Palpitations
  4. Paradoxical Embolism:
    • Stroke or transient ischemic attack
    • Systemic embolic events
    • More common in adults but can occur in children
  5. Associated Syndromes and Genetic Disorders:
    • Part of a syndromic presentation (e.g., Holt-Oram syndrome)
    • Associated with chromosomal abnormalities (e.g., Down syndrome)
    • May present with features of the underlying genetic disorder along with ASD
Viva Questions and Answers
  1. Q: What is an atrial septal defect (ASD)?
    A: An atrial septal defect is a congenital heart defect characterized by an opening in the interatrial septum, allowing blood flow between the left and right atria. It is one of the most common congenital heart defects, accounting for approximately 6-10% of all congenital heart diseases.
  2. Q: What are the different types of atrial septal defects?
    A: The main types of ASDs are:
    • Secundum ASD (most common, 75% of cases): Located in the central part of the atrial septum
    • Primum ASD (15-20%): Located in the lower part of the atrial septum, often associated with atrioventricular canal defects
    • Sinus venosus ASD (5-10%): Located near the entry of the superior or inferior vena cava
    • Coronary sinus ASD (rare): Defect in the wall between the coronary sinus and the left atrium
  3. Q: What is the pathophysiology of an ASD?
    A: In an ASD, blood flows from the left atrium to the right atrium due to the pressure difference between the two chambers. This left-to-right shunt leads to:
    • Increased blood flow to the right ventricle and pulmonary arteries
    • Right ventricular volume overload and eventual dilation
    • Increased pulmonary blood flow
    • If large and untreated, can lead to pulmonary hypertension and right ventricular failure over time
  4. Q: What are the classic auscultatory findings in a patient with ASD?
    A: Classic auscultatory findings include:
    • Fixed split S2: The split in the second heart sound does not vary with respiration
    • Systolic ejection murmur: Grade 2-3/6 at the left upper sternal border due to increased flow across the pulmonary valve
    • Mid-diastolic flow rumble at the lower left sternal border (in large ASDs)
  5. Q: How does an ASD affect the ECG?
    A: ECG findings in ASD may include:
    • Right axis deviation
    • Incomplete or complete right bundle branch block
    • Right ventricular hypertrophy in advanced cases
    • Prolonged PR interval (especially in primum ASD)
  6. Q: What are the typical chest X-ray findings in a patient with ASD?
    A: Chest X-ray findings may include:
    • Enlarged cardiac silhouette (mainly right atrium and right ventricle)
    • Increased pulmonary vascular markings
    • Prominent main pulmonary artery segment
    • In sinus venosus ASD, there may be a characteristic figure-of-8 appearance
  7. Q: How is an ASD diagnosed?
    A: ASD is typically diagnosed through:
    • Clinical presentation and physical examination
    • Echocardiography (transthoracic or transesophageal): Primary diagnostic tool
    • ECG and chest X-ray: Supportive findings
    • Cardiac MRI or CT: For complex cases or pre-procedural planning
    • Cardiac catheterization: Rarely needed for diagnosis, may be used for hemodynamic assessment in complex cases
  8. Q: What are the indications for closure of an ASD?
    A: Indications for ASD closure include:
    • Significant left-to-right shunt (Qp:Qs > 1.5:1)
    • Evidence of right ventricular volume overload
    • History of paradoxical embolism
    • Symptomatic patients (e.g., exercise intolerance, frequent respiratory infections)
    • Generally, closure is recommended for all ASDs >5mm by age 2-5 years
  9. Q: What are the methods available for ASD closure?
    A: ASD closure can be achieved through:
    • Transcatheter device closure: Preferred for secundum ASDs with suitable anatomy
    • Surgical closure: For large secundum ASDs, primum ASDs, sinus venosus ASDs, or when transcatheter closure is not feasible
  10. Q: What are the contraindications for transcatheter ASD closure?
    A: Contraindications include:
    • Primum or sinus venosus ASD
    • Very large secundum ASD (>38mm) without adequate rim
    • Multiple ASDs that cannot be covered by a single device
    • Associated lesions requiring surgical repair
    • Active endocarditis or other systemic infection
    • Intracardiac thrombus
  11. Q: What are the potential complications of untreated ASD?
    A: Potential complications include:
    • Right ventricular failure
    • Pulmonary hypertension
    • Atrial arrhythmias (e.g., atrial fibrillation, atrial flutter)
    • Paradoxical embolism and stroke
    • Eisenmenger syndrome (in rare, longstanding cases)
  12. Q: How does ASD differ from patent foramen ovale (PFO)?
    A: Key differences include:
    • ASD is a true defect in the atrial septum, while PFO is a normal fetal communication that fails to close after birth
    • ASDs typically have continuous left-to-right shunting, while PFOs have intermittent right-to-left shunting
    • ASDs often require closure, while most PFOs do not require intervention
    • ASDs can lead to right heart volume overload, which is not typically seen in PFO
  13. Q: What is Lutembacher syndrome?
    A: Lutembacher syndrome is a rare combination of:
    • Congenital atrial septal defect (usually secundum type)
    • Acquired mitral stenosis (typically rheumatic)
    This combination alters the hemodynamics and can mask the typical findings of each individual lesion.
  14. Q: How does pregnancy affect women with unrepaired ASD?
    A: In pregnancy, women with unrepaired ASD may experience:
    • Increased risk of paradoxical embolism due to hypercoagulable state
    • Increased right-to-left shunting due to increased venous return
    • Potential for heart failure symptoms due to increased cardiovascular demands
    • Increased risk of arrhythmias
    Most women with small to moderate ASDs tolerate pregnancy well, but large defects may require pre-pregnancy intervention.
  15. Q: What follow-up is required after ASD closure?
    A: Follow-up after ASD closure typically includes:
    • Immediate post-procedure echocardiogram to confirm device position or surgical repair
    • ECG to assess for arrhythmias
    • Follow-up echocardiogram at 1, 6, and 12 months, then annually
    • Antiplatelet therapy (usually aspirin) for 6 months after device closure
    • Endocarditis prophylaxis for 6 months after closure, then lifelong for surgical closure with prosthetic material
  16. Q: What is the natural history of untreated ASD?
    A: The natural history of untreated ASD varies:
    • Small defects (<5mm) may close spontaneously in the first few years of life
    • Moderate defects may remain asymptomatic until adulthood
    • Large defects can lead to symptoms in childhood or early adulthood
    • By age 40, 90% of untreated patients have symptoms
    • Complications increase with age: arrhythmias, right heart failure, pulmonary hypertension
  17. Q: How does ASD affect exercise tolerance in children?
    A: ASD can affect exercise tolerance by:
    • Causing increased pulmonary blood flow, leading to dyspnea on exertion
    • Right ventricular volume overload, reducing cardiac efficiency
    • Potential for exercise-induced pulmonary hypertension in large defects
    • Increased risk of arrhythmias during exercise
    However, many children with small to moderate ASDs may have normal exercise tolerance.
  18. Q: What genetic syndromes are associated with ASD?
    A: Genetic syndromes associated with ASD include:
    • Holt-Oram syndrome (TBX5 gene mutation)
    • Down syndrome (Trisomy 21)
    • Ellis-van Creveld syndrome
    • Noonan syndrome
    • CHARGE syndrome
    • Williams syndrome (rare association)
  19. Q: How does a sinus venosus ASD differ from a secundum ASD?
    A: Key differences include:
    • Location: Sinus venosus ASD is located near SVC or IVC entry, secundum in central septum
    • Associated anomalies: Sinus venosus often has partial anomalous pulmonary venous return
    • Embryology: Different developmental origins
    • Treatment: Sinus venosus always requires surgical repair, secundum can often be closed by device
    • Diagnosis: Sinus venosus may be harder to visualize on transthoracic echocardiography
  20. Q: What are the potential complications of transcatheter ASD closure?
    A: Potential complications include:
    • Device embolization
    • Cardiac perforation or erosion
    • Arrhythmias (e.g., atrial fibrillation, heart block)
    • Residual shunt
    • Thromboembolism
    • Allergic reaction to device material (rare)
    • Infection
  21. Q: How does an ASD affect pulmonary vascular resistance over time?
    A: The effect of ASD on pulmonary vascular resistance (PVR) typically follows this pattern:
    • Initially, PVR is normal or low due to the compliant pulmonary vasculature
    • Chronic increased pulmonary blood flow can lead to gradual changes in pulmonary vasculature
    • Over years to decades, some patients may develop increased PVR
    • In rare cases, severe pulmonary vascular disease can develop, leading to Eisenmenger syndrome
    • The risk of developing pulmonary hypertension increases with age and size of the defect
  22. Q: What is the role of cardiac MRI in the evaluation of ASD?
    A: Cardiac MRI is valuable in ASD evaluation for:
    • Accurate quantification of shunt fraction (Qp:Qs ratio)
    • Detailed anatomy of complex defects, especially sinus venosus ASD
    • Assessment of associated anomalies, such as partial anomalous pulmonary venous return
    • Evaluation of right ventricular size and function
    • Pre-procedural planning for complex cases
    • Follow-up assessment after repair, especially for surgical cases
  23. Q: How do you manage a patient with ASD and pulmonary hypertension?
    A: Management of ASD with pulmonary hypertension involves:
    • Careful hemodynamic assessment, usually requiring cardiac catheterization
    • Evaluation of pulmonary vascular reactivity with vasodilator testing
    • If pulmonary hypertension is reversible, proceed with ASD closure
    • If borderline, consider fenestrated device closure or staged approach
    • In severe, irreversible cases (Eisenmenger syndrome), ASD closure is contraindicated
    • Pulmonary vasodilator therapy may be considered in selected cases
    • Regular follow-up to monitor progression of pulmonary hypertension
  24. Q: What are the indications for fetal echocardiography in suspected ASD?
    A: Fetal echocardiography may be indicated in cases of:
    • Family history of congenital heart disease, especially ASD
    • Maternal medical conditions associated with increased risk of CHD (e.g., diabetes, phenylketonuria)
    • Exposure to teratogens associated with CHD
    • Abnormal obstetric ultrasound findings suggestive of cardiac anomaly
    • Fetal arrhythmia or hydrops fetalis
    However, it's important to note that small ASDs are often not detectable prenatally.
  25. Q: How does an ASD affect the risk of stroke in children and young adults?
    A: ASD can increase the risk of stroke through:
    • Paradoxical embolism: Right-to-left shunting of venous thrombi
    • Increased risk of atrial arrhythmias, which can lead to thromboembolism
    • Potential for in situ thrombus formation in dilated right atrium
    • The risk increases with age and size of the defect
    • Cryptogenic stroke in a young patient should prompt evaluation for ASD or PFO
  26. Q: What are the considerations for anticoagulation in patients with ASD?
    A: Anticoagulation considerations in ASD patients include:
    • Routine anticoagulation is not recommended for uncomplicated ASD
    • Antiplatelet therapy (usually aspirin) for 6 months after device closure
    • Anticoagulation may be needed if atrial arrhythmias develop
    • Consider anticoagulation in patients with history of paradoxical embolism
    • In Eisenmenger syndrome, anticoagulation is controversial and should be individualized
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