ASD Flow across the defect

In ASD Flow across the defect occurs in

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[A] Mostly in Systole
[B] Only diastole
[C] Only systole
[D] Both systole and diastole

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ASD Flow across the defect

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1. Flow across the ASD defect occurs in both systole and diastole.
2. Predominantly left to right, but transient right-to-left shunts are common, particularly with isometric strain.
3. Major shunt flow occurs during diastole.
4. During diastole blood in each atrium has 2 alternative pathways:
   • Following the normal route through the AV valve to the ventricle on that side or
   • Passing through the ASD to fill the opposite ventricle.
5. Direction of flow across the ASD during diastole is determined by the instantaneous differences in the compliance and the capacity of the 2 ventricles.
6. Easier to fill the more compliant RV – ASD patient, the difference in chamber compliance favors a left-to-right shunt because the blood in the LA finds it easier to fill the more compliant RV.

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