Can a mid diastolic murmur be present in atrial septal defect (ASD)?

Mid-Diastolic Murmur in Atrial Septal Defect

Yes, a mid-diastolic murmur can be present in atrial septal defect (ASD) due to increased blood flow across the normal tricuspid valve. 1

Pathophysiology of Murmurs in ASD

• Mid-diastolic murmurs in ASD occur due to increased diastolic blood flow across the normal tricuspid valve, resulting from the left-to-right shunting through the defect 1
• This increased flow creates a relative disproportion between the tricuspid valve orifice size and the diastolic blood flow volume, generating the murmur 1
• The mid-diastolic murmur is detected in approximately 75% of ASD cases, specifically due to relative tricuspid stenosis from the increased flow 2

Characteristic Auscultatory Findings in ASD

• The classic auscultatory findings in ASD include:
  • Loud first heart sound 2
  • Widely fixed split second heart sound (does not vary with respiration) 3, 2
  • Soft ejection systolic murmur at the upper left sternal border 3, 2
  • Mid-diastolic murmur at the lower left sternal border (tricuspid area) 2

Hemodynamic Correlation

• The presence of a mid-diastolic murmur correlates with the pulmonary-to-systemic flow ratio (Qp/Qs), which typically ranges from 1.7 to 6.3 in ASD patients 2
• Higher shunt volumes lead to more pronounced mid-diastolic murmurs due to greater tricuspid flow 2
• The left-to-right shunting is determined by the compliance difference between right and left ventricles 4

Clinical Significance

• The mid-diastolic murmur may persist until ASD closure, after which it typically resolves as the tricuspid flow normalizes 2
• This murmur helps differentiate ASD from other congenital heart defects 3
• The murmur is a right-sided finding and thus typically increases with inspiration 1

Diagnostic Considerations

• The mid-diastolic murmur should be distinguished from other causes of diastolic murmurs, such as mitral stenosis or tricuspid stenosis 1
• Echocardiography is essential to confirm the diagnosis and assess the size, location, and hemodynamic impact of the ASD 5
• The murmur may be less prominent in elderly patients with ASD who have developed pulmonary hypertension or right ventricular dysfunction 5, 4

Post-Repair Findings

• Following successful ASD repair, the mid-diastolic murmur typically resolves as the tricuspid flow normalizes 2
• However, some patients may continue to have residual murmurs in the early post-operative period 2
• Long-standing ASDs may lead to persistent right heart enlargement even after repair, particularly if closure occurs at an older age 5, 6