This anomaly is due to a defect in the tricuspid valve (TV) with the septal and posterior leaflets displaced down into the right ventricle, while the anterior leaflet is malformed and abnormally attached to the RV free wall (see figure 23D). This valve often allows blood to regurgitate from the small RV back into the large RA. Eighty percent of these patients have ASD's through which right-to-left shunting of blood may occur with cyanosis. Such patients are at risk for a paradoxical embolus (blood clot) from the RA through the LA to the brain with abscess(instead of the normal route of an embolus from the legs to the lungs via the right ventricle through the pulmonary valve)and sudden death.

There is usually a heart murmur. EKG abnormalities are often present including WPW syndrome,an atrial tachycardia or rapid heart beat(see figure 1, 2, 3A, 3B). Twenty percent have an accessory electrical pathway between the atrium and ventricle (see figure 1) to account for the cardiac arrhythmias.

An echocardiogram can define the abnormalities, and a color Doppler imaging study can determine the presence and size of interatrial shunting.

Management involves prevention of complications, such as heart infection, prevented with antibiotic prophylaxis. Heart failure is treated with diuretics (diuril, lasix, etc) (to eliminate fluid) and digoxin (a heart drug to improve heart muscle contractions). Arrhythmias may be treated with medication or catheter ablation (see figure 3b, 11).

Repair or replacement of TV in conjunction with closure of the interatrial communication is recommended in older patients with severe symptoms despite medical therapy and heart enlargement.