Left superior vena cava to left atrial communication diagnosed with radionuclide angiocardiography and with differential right to left shunting.

Anomalous left superior vena cava to left atrial communication, although rare, should be considered in the presence of a right to left shunt without right ventricular hypertrophy, especially when the cause of the shunt cannot be identified at cardiac catheterization. We present a case with a diagnosis based on two radionuclide techniques. Nuclear angiography, performed after the injection of technetium-99m pertechnetate into the left arm, demonstrated the anomaly. Total body scans performed after intravenous injections of labeled albumin microspheres indicated 65% right to left shunting of left arm venous return but only 9% shunting of right arm venous return, findings that are diagnostic of left superior vena cava to left atrial communication.