Case 4—2002 Near-fatal pulmonary embolism in the immediate postoperative period after off-pump coronary artery bypass graft surgery

A 72-year-old man with known coronary artery disease (exertional angina and 2 previous myocardial infarctions) was admitted to the hospital with a new non–Q-wave myocardial infarction as evidenced by elevated serum troponin concentration and non–Q-wave electrocardiogram changes in the anteroseptal leads. Acute management included intravenous nitrate therapy and subcutaneous enoxaparin, 80 mg twice a day; and long-term cardiac medications, including aspirin, furosemide, isosorbide mononitrate, atenolol, and ramipril, were continued. Thrombolytic therapy was not administered on this occasion. Relevant medical history included noninsulin-dependent diabetes mellitus and a dual-chamber pacemaker (Pacesetter Paragon III; St Jude Medical, St. Paul, MN), which was inserted 5 years previously for symptomatic bradycardia. The patient underwent a subsequent exercise stress test using a modified Bruce protocol. Electrocardiogram changes showed anterior ST depression at 7 minutes. He was referred for coronary angiography, which revealed significant stenosis of the left mainstem (60%), proximal anterior descending (99%), and midcircumflex (60%) coronary arteries. The right coronary artery had minor plaques in the midvessel only. Left ventricular function was preserved on ventriculography. Two hours after coronary angiography, the patient suffered further episodes of angina pectoris that responded to intravenous nitrate therapy. This condition was associated with 2 episodes of collapse on standing. The attending physician noted symptomatic bradycardia and attributed it to the vasodilatory effects of nitrate therapy. In view of his further chest pain, an intravenous infusion of unfractionated heparin was started at 12 U/kg/h. The heparin was titrated to maintain an activated partial thromboplastin ratio of twice control and was continued until surgery. The patient’s pacemaker function was not tested preoperatively, and he did not undergo a preoperative transthoracic echocardiography examination. Off-pump coronary artery bypass graft (OP-CAB) surgery was done the next day using the Octopus (Medtronic Inc, Minneapolis, MN) stabilizing device. Monitoring included electrocardiogram, peripheral oxygen saturation, end-tidal gas composition, invasive blood pressure monitored through the right radial artery, and central venous pressure monitoring. During the performance of coronary anastomosis, full systemic heparinization with 240 mg of unfractionated heparin (300 U/kg) was used. Effectiveness of anticoagulation was monitored intraoperatively by the activated coagulation time (ACT), maintaining an ACT 400 seconds throughout coronary artery grafting. On completion of the anastomoses, the heparin was fully reversed using 240 mg of protamine sulfate (1:1 ratio). The left internal mammary artery was found unsuitable after harvesting, and a solitary saphenous vein graft was used from the aorta to the distal left anterior descending artery. The procedure was well tolerated without any hemodynamic compromise, and no inotropic support was required. After surgery, the patient was returned to the intensive care unit. The first 2 hours in the intensive care unit were complicated by persistent systolic hypotension of 75 mmHg, attributed to excessive bleeding from the left pleural tube. Approximately 750 mL of blood drained. This hypotension was unresponsive to transfusion of 6 U of packed red blood cells and 2,000 mL of colloid. Inotropic support (epinephrine, 0.28 g/kg/min) now was required. At this point, a sudden marked change in central venous pressure (from 7 to 20 mmHg) was noted, and transesophageal echocardiography (TEE) was performed immediately to exclude cardiac tamponade. TEE examination revealed preserved systolic function and an underfilled left ventricle. In contrast, the right ventricle was dilated and akinetic. Trivial tricuspid regurgitation was noted. The permanent pacing lead was also noted within the right ventricle. In addition to a dilated right ventricle, the main and right branches of the pulmonary artery were dilated There was no evidence of tamponade; however, a large collection of blood was seen *M.J. Platt, S. Davies, and B. Riedel