Mechanism of wide fixed split in Atrial septal defect (ASD)

  • First you can review the Mechanism of normal split in second heart sound
  • In case of atrial septal defect, the right atrium receives blood from the left atrium in addition to the normal venous return
  • Due to the increased amount of blood reaching the right ventricle, it takes a longer time to eject the blood
  • Hence the pulmonary valve takes longer to close and we appreciate a wide split (In both inspiration and expiration)

So, why does it cause a wide fixed split instead of a wide variable split?

  • During inspiration, the blood flow through the vena cava increases, whereas that from the left atrium decreases
  • Whereas during expiration, blood flow through the vena cava decreases, and that from the left atrium increases
  • During the respiratory cycle, the blood flow through the vena cava and left atrium vary reciprocally
  • Hence the wide fixed split

You can also read about : Split of second heart sound in Ventricular Septal Defect (VSD)

One Comment

Add a Comment

Your email address will not be published. Comments will be displayed only after moderation.

Read previous post:
Mechanism of physiological split in second heart sound

During inspiration the aortic component of the second heart sound is heard about 0.02 to 0.08 seconds before the pulmonary component....

Close