Deep venous thrombosis. Implications after open heart surgery. We reviewed the cases of 10,638 cardiac surgical patients to determine the incidence of deep vein thrombosis (DVT) after open heart surgery (OHS). Seventy-seven patients (0.7 percent) had DVT. Group 1 included 36 patients who had DVT without pulmonary embolism (PE). Occurrence was equal in either leg. Anticoagulation with heparin and warfarin sodium (Coumadin) was employed as treatment. Extension of hospital stay was 10.8 days. Group 2 consisted of 41 patients who experienced PE 9.9 days after OHS. Sixteen patients had known DVT and were receiving heparin. In 25 patients, PE was the first event. Risk factors for PE included perioperative myocardial infarction (16 percent), atrial fibrillation (41 percent); blood type A (70 percent) (p less than 0.05), and coronary artery bypass graft (CABG) (98 percent). Twenty-four patients were treated with anti-coagulation alone. Six died of recurrent PE; mortality was 25 percent. Seventeen patients received anticoagulation plus inferior vena cava (IVC) interruption using a Hunter balloon. There were no recurrent PEs and there was one death from myocardial infarction (6 percent). Deep vein thrombosis and PE are rare complications of OHS. Routine prophylaxis with either heparin or warfarin is unnecessary. Patients with DVT, atrial fibrillation (AF), and perioperative myocardial infarction are at high risk of PE. Aggressive diagnosis to identify major venous thrombi along with anticoagulation and early consideration of IVC interruption are recommended for these patients. Patients who have undergone OHS and who have PE are at an unusually high risk for recurrent PE with death and are more safely treated with IVC interruption and anticoagulation than anticoagulation alone. 