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
due to increased pulmonary hangout interval