Ebstein's anomaly. Ebstein's anomaly is a rare heart defect that's present at birth (congenital). In ebstein's anomaly, your tricuspid valve — the valve between the chambers on the right side of your heart — doesn't work properly. Blood leaks back through the valve, making your heart work less efficiently. Ebstein's anomaly may also lead to enlargement of the heart or heart failure. If you have no signs or symptoms.