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Queen's University at Kingston Kingston, Ontario, K7L 2V7 Canada
Pseudoaneurysm formation at the graft anastomotic site after coronary artery bypass surgery is rarely diagnosed in patients during life. A large pseudoaneurysm presented as a pulsatile mass at the sternotomy incision.
A 46-year-old man had a sternotomy and quadruple saphenous vein bypass procedure that was complicated by mediastinitis and sternal dehiscence. Methicillin-resistant Staphylococcus aureus infection was treated with sternal débridement and vancomycin. Two months later, the patient presented with fever, malaise, and chest wall tenderness associated with elevated WBC and erythrocyte sedimentation rate. Coronary angiography revealed a 4-cm pseudoaneurysm at the anastomosis of the right coronary artery vein graft and aorta. The pseudoaneurysm was repaired with a patch (synthetic graft material). Methicillin-resistant S. aureus was cultured. Post-operatively, the patient developed cerebral edema, seizures, and coma. The sternotomy incision oozed dark blood and was unstable. Five days later, there was a pulsatile mass at the sternotomy incision. Unenhanced helical CT of the thorax showed a low-attenuation mass extending from the aorta into the subcutaneous tissues (Fig. 2A). Contrast-enhanced CT findings confirmed the diagnosis of a pseudoaneurysm (Fig. 2B). It ruptured spontaneously shortly thereafter resulting in the patient's death.
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Patients with aortocoronary grafts may develop a true aneurysm caused by atheromatous disease or a pseudoaneurysm caused by infection, faulty suture technique, operative vein graft damage, or an intrinsic weakness of the graft or proximal artery [1]. A pseudoaneurysm is more common than a true aneurysm, usually occurs at the graft anastomosis with the aorta, and is usually an early complication. Rupture, thrombosis, graft occlusion, superior vena cava obstruction, embolization, and fistula formation to the right ventricle may complicate pseudoaneurysm [1]. It occurs in 0.2% of all aortocoronary bypass procedures and is the cause of death in approximately 3% of all late deaths [2].
Mediastinitis complicates 0.4-5% of aortocoronary bypass procedures and is responsible for at least 50% of the cases of pseudoaneurysm formation [3]. The prevalence of pseudoaneurysm formation in patients with Dacron (name of manufacturer of Dacron, city, state/country) grafts is approximately 5.5% [4].
The diagnosis of pseudoaneurysm requires a high clinical index of suspicion because the patient may be asymptomatic or have nonspecific symptoms and signs. Diagnosis is critical because pseudoaneurysm is a surgical emergency. CT is a particularly valuable technique for the diagnosis of post-surgical complications of sternotomy and aortocoronary bypass surgery. CT is efficacious for the diagnosis of mediastinitis, sternal osteomyelitis and dehiscence, hematoma, and pseudoaneurysm. Enhanced CT permits differentiation between abscess, hematoma, and pseudoaneurysm.
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