Types of Atrial Septal Defects

Patients with large atrial septal defects may be asymptomatic or present with exertional fatigue and dyspnea as well as palpitations. Typical bedside findings reflect marked right ventricular volume overload and include equal jugular venous "a" and "v" waves, prominent rigth-sided precordial impulses of the pulmonary artery and right ventricle, wide, fixed splitting of the second heart sound, a systolic murmur of right ventricular outflow and a mid diastolic murmur of enhanced right ventricular filling.

In a large atrial septal defect, there is a functionally single atrium with no pressure gradient between the atria. Blood shunts from left-to-right, as the right ventricle is more compliant than the left and offers less resistance to flow. Because of the common atrial effect, flow to the ventricles show no significant respiratory variation. Pulmonary compliance also shows little respiratory change, as the pulmonary vascular bed is overfilled.

In contrast, smaller atrial septal defects typically have a pulmonary ejection murmur and wider than normal, but not fixed splitting of the second heart sound and no diastolic right ventricular filling murmur.

Those with very small defects may have no findings to distinguish them from normal.