Mid-Diastolic Murmur in Atrial Septal Defect

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 2, 1

Clinical Significance

• 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 2, 1