People with atrial septal defect murmur. when is it dangerous to you?

Stroke and infection: Because of an initial left-to-right shunt, increased volume and pressure in the pulmonary circuit lead to pulmonary hypertension and eventual right-to-left shunt. Clot and infection may originate at this abnormal septal defect that may travel from the heart to the brain causing stroke.

Good question: Atrial septal defects are holes in the wall separating the right and left atria. If the holes are very tiny, they may heal completely and disappear. If the holes are small, they may continue to exist, but may be harmless long-term. Large atrial septal defects can cause heart failure in the long term and often need surgical repair to prevent premature death.