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What are the Murmurs in atrial septal defect?

ASD is a condition where there is abnormal communication between the right and left atria resulting in shunting of blood from left to right atria.
What is the classical murmur of atrial septal defect ?
The classical murmur is a crescendo - decrescendo ejection systolic murmur in the pulmonary area which peaks in early or mid systole.
This murmur is produced due to the rapid ejection of the large right ventricular stroke volume into the dilated pulmonary artery.
Sometimes flow murmur may be produced due to rapid blood flow through the peripheral pulmonary arteries. This can be heard as a systolic murmur over the right side of chest, axilla or back.
What are the causes of loud murmur in ASD ?
Loud murmur in ASD may be due to 
  • Large defect
  • ASD with mitral stenosis
  • ASD with pulmonary stenosis
What are the differential diagnosis of mid diastolic murmur at apex in ASD ?
Large ASD with tricuspid middiastolic murmur
ASD with acquired mitral stenosis
Differential diagnosis of ASD with PSM (Pansystolic murmur) at the apex - following are the causes ?
Ostium secondum ASD with mitral valve prolapsed
Ostium primum ASD with mitral regurgitation