Thromboembolic disease is a potentially severe pathology. When its clinical feature implies a massive occlusion of the arterial pulmonary tree and a cardiac failure is ensued, it can be seriously life threatening even for young patients. Less frequent features as right or left atrium thrombosis could increase morbidity and mortality of this disease. We report a case of massive right pulmonary embolism (PE) with entrapped thrombus in patent foramen ovale and right heart failure in a 32- year-old man. Transthoracic echocardiography showed a right atrial thrombus attached to the inter-atrial septum. Following the diagnosis of right heart thrombosis with massive PE, infusion of tissue type plasminogen activator (100 mg in two hours) was administered. Echocardiography performed two days after thrombolysis showed a significant decrease in the right ventricular size and complete lysis of the thrombus in the right heart. By genetic examination, he proved to have factor V 'Leiden' gene and two thrombophilia genes, all of which were positive in the heterozygous state. He had also a high serum homocysteine.