Epidemiology Etiology Types by location: Membranous (perimembranous): ~80%, most common Muscular (trabecular): may close spontaneously Inlet (AV canal type): assoc. w/ Down syndrome Outlet (subarterial/supracristal) Pathophysiology Clinical features General Small defects: usually asymptomatic Medium-sized or large defects Lead to heart failure by the age of 2–3 months Become symptomatic after high pulmonary vascular resistance (PVR) present at birth starts to decrease: ↓ PVR → ↓ right ventricular pressure → ↑ left-to-right shunt → symptoms So it may not be heard at birth Diagnostics Treatment