Surgical embolectomy (SE) is performed though a median sternotomy using mild hypothermic or normothermic cardiopulmonary bypass (CPB). The main pulmonary artery is opened with a longitudinal incision, which can be extended into the right and left pulmonary artery branches. The thrombotic material is extracted using a special forceps and by assisting suction. To ensure complete clot removal the right and left pulmonary artery branches a flexible surgical angioscope can be used to inspect the segmental arteries. Massage of the lungs is not performed to avoid additional damage to the lung parenchyma. The right atrium and ventricle are routinely explored, all clot material is carefully removed and a patent foramen ovale if present is closed with a 4-0 running suture. The pulmonary arteriotomy is closed with a running suture, and the patient is weaned from CBP after declamping of the aorta. The patient is transferred to the intensive care unit and is treated with intravenous unfractioned heparin (initial dosage of 1000Ul/24h, the goal is to achieve an activated partial thromboplastin-time ratio of at least twice the control value) starting six hours after surgery. All patients receive in the follow-up period oral anticoagulation with warfarin (starting on postoperative day one) with an International Normalized Ratio (INR) target of 2.5± 0.5 for at least 3 months.