Embolic occlusion of a patent foramen ovale: a cause of false negative contrast echocardiogram.

A 74-year-old man who had dyspnea and cyanosis demonstrated venous thrombosis and multiple lung ventilation-perfusion mismatches suggesting pulmonary emboli. Transthoracic echocardiography demonstrated a right atrial mass and a microbubble contrast study did not reveal right-to-left shunt. Transesophageal echocardiography revealed an embolus entrapped in the foramen ovale projecting into the left atrium that was subsequently removed. Embolic occlusion of patent foramen ovale is an important cause of false negative microbubble contrast study.