True about ASD –
Hemodynamics ofASD                              
There is abnormal connection between left and right atrium, which is due to defect in atrial septum (not a patent foramen ovale).

Blood flows from left atrium to right atrium because left atrium has slightly higher pressure than right atrium → Left to right shunt.
Because the pressure difference between two atria is small, blood passes at a narrow pressure difference No shunt murmur.
There is volume overload to right atrium because of left to right shunt →.Right atrial dilatation and hypertrophy.
During diastole large amount of blood passes from right atrium to right ventricle through tricuspid valve → delayed diastolic murmur and accentuation of first heart sound.
Volume overload to right ventricle → Right ventricular hypertrophy that produces parasternal heeve.
Large blood volume passes through pulmonary valve → Pulmonary ejection murmur.
Prolonged blood passage along pulmonary valve causes delayed closure of pulmonary valve → P2 is delayed and accentuated, wide split and fixed S2.
Increased blood flow through pulmonary circulation → Pulmonary plethora that may cause pulmonary hypertension