- Congenital inter-atrial connection
- First manifestation can be in adulthood if smaller, w/patholphysiology developing over time→ up to 30s or 40s
- Typically L to R shunting
- Slowly progressive doe
- Paradoxical emboli
- Atrial dysrhythmias
- Rarely platypnea-orthodexia→ Sob worse w/sitting up; Sob relieved by lying down
- Fixed & widely split S2
- Sometimes murmur from high flow across TV or PV
- Stroke if paradoxical embolous