Table 4.14 - Characteristics of Atrial Septal Defects.

Large ASD gives a common filling pressure for both ventricles.
As RV wall thins, L --> R shunt develops, producing dilatation of RA, RV & pulmonary vessels; seen on ECG, chest X-ray, & echocardiography.
ASD is silent! However, increased flow through tricuspid valve gives a mid-diastolic rumbling murmur, and a systolic ejection murmur due to increased pulmonary valve flow (fixed wide-split S₂).
O₂ step-up at atrial level by cardiac catheterization permits calculation of shunt flow.

Normal ASD

RA 2 5

LA 6 5

RV 20, 70% 40, 85%

PA 20 30

svc 70% 70%

LV 100 100