Atrial septal defect (ASD) ❤️

Related Subjects: |Congenital Acyanotic Heart Disease |Congenital Cyanotic Heart Disease |Cardiac Embryology |Cyanosis - Central and Peripheral |Down's syndrome (Trisomy 21) |Tetralogy of Fallot |Patent Foramen Ovale (PFO) |Ventricular Septal defect (VSD) |Atrial Septal defect (ASD) |Ebstein anomaly |Eisenmenger's syndrome

🫀 In ASD, the murmur is not due to flow across the septum itself, but rather increased right-sided flow → producing an ejection systolic murmur (ESM) over the pulmonary valve. 🔊 Fixed splitting of S2 is a hallmark. 🧪 Surgery/device closure is usually indicated if Qp:Qs > 1.5 or if there is significant right heart dilatation. 💉 Risk of endocarditis is low.

📖 About

• ASD = congenital defect with an abnormal opening between the atria → left-to-right shunt.
• Results in volume overload of the RA & RV, and ↑ pulmonary blood flow.
• ~10% of congenital heart disease. More common in ♀ and in Down’s syndrome.

⚙️ Pathophysiology

• Oxygenated blood from LA → RA → RV → pulmonary artery → pulmonary hypertension risk.
• RA & RV become dilated over time → right heart failure.
• Chronic shunt may cause pulmonary vascular remodelling → Eisenmenger syndrome (shunt reversal & cyanosis).

🔎 Types of ASD

• Ostium Secundum (70%): Commonest. Foramen ovale region. Often + mitral valve prolapse. ECG: RBBB + RAD.
• Ostium Primum (15%): Near AV valves → partial AVSD. Often with MR/TR. Associated with Down’s, Noonan, Klinefelter. ECG: RBBB + LAD + 1° AV block.
• Sinus Venosus (15%): Near SVC/IVC. Often anomalous pulmonary venous drainage. ECG: RBBB.
• Unroofed Coronary Sinus (<1%): Rare, coronary sinus drains to LA.

🩺 Clinical Presentation

• Often silent in childhood → may present later.
• Symptoms: Dyspnoea, fatigue, recurrent chest infections, palpitations (AF/flutter).
• Exam:
  • 🌟 Fixed, wide split S2.
  • ESM at left upper sternal edge (↑ flow across PV).
  • Mid-diastolic murmur at LLSE (↑ flow across TV).
• Advanced: Signs of RHF (JVP ↑, hepatomegaly, oedema).

🧪 Investigations

• CXR: Cardiomegaly, pulmonary plethora, enlarged RA/RV.
• ECG:
  • Secundum: RBBB + RAD.
  • Primum: RBBB + LAD + 1° AV block.
• Echocardiography: Key test – visualises defect, shunt, RV dilatation, valve involvement.
• Cardiac MRI: Detailed anatomy, esp. sinus venosus.
• Right Heart Cath: Measures Qp:Qs ratio & pulmonary pressures.

⚠️ Complications

• 💨 Pulmonary hypertension.
• 📉 Right heart failure.
• ❤️ Atrial arrhythmias (AF/flutter).
• 🧠 Paradoxical embolism → stroke.
• 🔄 Eisenmenger syndrome if untreated.

💊 Management

• Monitoring: Small, asymptomatic ASDs → echo follow-up.
• Closure Indications: Qp:Qs > 1.5 or evidence of RV dilatation.
• Catheter device closure: Secundum defects (minimally invasive).
• Surgical closure: Needed for primum, sinus venosus, or very large secundum ASDs. Operative mortality <1% in specialist centres.
• Anticoagulation: If AF or paradoxical embolism.
• Prognosis: Excellent if repaired before pulmonary HTN develops.

📚 Reference

• AHA/ACC Guidelines for the Management of Patients with Atrial Septal Defects

🩺 Case 1 - Child with Recurrent Chest Infections

A 6-year-old girl is evaluated for recurrent chest infections and poor growth. Exam reveals a fixed split of the second heart sound and a systolic murmur at the left upper sternal edge. Echocardiography shows a secundum ASD with right atrial and right ventricular dilatation. Management: 🩺 Elective closure (percutaneous device or surgical repair) usually in early childhood to prevent long-term complications. Avoid: ❌ Delaying closure beyond adolescence, as this increases risk of pulmonary hypertension and arrhythmias.

🩺 Case 2 - Adult with Incidental Murmur

A 35-year-old woman is found to have a systolic murmur during a routine check. She is asymptomatic, but echo demonstrates a secundum ASD with significant left-to-right shunt (Qp:Qs > 1.5). Management: 💊 Closure indicated if shunt is significant and RV dilatation present, even if asymptomatic. Endocarditis prophylaxis not routinely required. Avoid: ❌ Assuming asymptomatic means benign - late complications (AF, RV failure) can still occur.

🩺 Case 3 - Elderly Patient with Pulmonary Hypertension

A 70-year-old man presents with exertional dyspnoea and ankle swelling. Exam shows elevated JVP, a loud P2, and a systolic murmur. Echo confirms an unrepaired secundum ASD with severe pulmonary hypertension and right heart failure. Management: 🚑 Supportive therapy for right heart failure (diuretics, oxygen). ASD closure not advised if pulmonary vascular resistance is very high and right-to-left shunt has developed (Eisenmenger physiology). Palliative and specialist pulmonary hypertension care considered. Avoid: ❌ Closing the defect in irreversible pulmonary hypertension - can worsen right-sided failure.