The tricuspid leaflets are abnormal and are displaced into the body of the right ventricle.
The septal leaflet is variably deficient or even absent.
The posterior leaflet is also variably deficient and there is a large 'sail-like' anterior leaflet that is the hallmark of this condition.
The abnormally located tricuspid orifice results in a part of the right ventricle lying between the atrioventricular ring and the origin of the valve, which is continuous with the right atrial chamber.
This proximal segment is known as the 'atrialized' portion of the right ventricle.
About 50% of the patients have either a patent foramen ovale or a secundum ASD, and 25% have one or more accessory atrioventricular conduction pathways.
The anomaly is said to be associated with maternal lithium ingestion.