Aortic Graft Pseudoaneurysm Secondary to Fracture of Sternal Wires

Abstract

A 74-year-old man with a previously placed ascending aortic graft was admitted to our hospital with a pulsating sternal mass, 2 days after an episode of severe coughing. Six months earlier, computed tomographic scanning had shown an intact aortic graft and no sternal wire fracture, but the wires had cut through the sternum. Computed tomographic scans at the current admission showed the patient to have 2 perforations of the ascending aortic graft, which led to 2 pseudoaneurysms and a large subcutaneous hematoma. In another view, a fractured sternal wire could be seen leading to one of the pseudoaneurysms.

We performed emergent surgery and found sternal separation, as well as 2 holes in the graft that coincided with the location of the fractured sternal wires. We successfully patched the graft; however, the patient had a cerebral ischemic stroke and died 2 weeks postoperatively. This case emphasizes the importance of early removal of loosening sternal wires. (Tex Heart Inst J 2003;30:240–2)

In September 2001, a 74-year-old man was admitted to the hospital with a pulsating sternal mass. Two days earlier, he had experienced severe coughing, followed by palpitations, cold sweating, and dyspnea. He noticed the sternal mass after that event. Six years earlier, he had undergone ascending aortic replacement for type A aortic dissection. He had been well postoperatively and had undergone regular follow-up examinations. A computed tomographic (CT) scan, taken 6 months before the present admission, had revealed an intact graft and no sternal wire fracture; however, the wires were loose and appeared to have cut through the sternum (Fig. 1). The sternum was stable with good union.

Fig. 1 Chest computed tomographic scan obtained 6 months prior to admission revealed no wire fracture, and the graft (G) was intact. However, the wire had cut through the sternum and seemed to have loosened (arrow).

On physical examination, the patient was afebrile and hemodynamically stable. The midline mass was situated in the upper half of the sternum and appeared pulsatile and erythematous. Results of blood tests revealed no leukocytosis, and the other blood chemistry results were within normal limits. A CT scan showed 2 pseudoaneurysms of the ascending aortic graft (Fig. 2); another image revealed a fractured sternal wire leading to one of the pseudoaneurysms (Fig. 3). Because of the risk of free rupture, the patient underwent emergent surgery.

Fig. 2 Chest computed tomographic scan made on the current admission shows 2 pseudoaneurysms (stars) arising from the ascending aortic graft (G) and a large subcutaneous hematoma (H). The arrowheads indicate the perforations.

Fig. 3 Chest computed tomographic scan shows a pseudoaneurysm (star) protruding from the graft (G). The arrow indicates the fractured sternal wire.

The reoperation was performed with use of femoro-femoral bypass for cooling the patient, and left ventricular apex venting was accomplished through a small left anterior thoracotomy. With the patient at a core temperature of 17°C, circulatory arrest was achieved. The skin was incised, and a large subcutaneous hematoma was found. The sternal wires were observed to be fractured, and separation of the sternum was also noted. After we removed the subcutaneous and mediastinal hematomas, we noted two 1.5-cm diameter holes with rough edges on the anterior surface of the graft. These holes coincided with the location of the fractured sternal wires. The anastomotic sites were intact and grossly free of infection. The holes were trimmed to form a single opening, which was then repaired with a Dacron patch. After de-airing of the heart, the patient was easily weaned from cardiopulmonary bypass at a core temperature of 36.5°C. The duration of total circulatory arrest was 18 minutes, and the duration of cardiopulmonary bypass was 188 minutes. The tissue specimen revealed no active inflammation microscopically. The patient's postoperative course was complicated by a cerebral ischemic stroke, and he died 2 weeks postoperatively of multiple-organ failure.

Comment

Pseudoaneurysms of the ascending aorta after cardiovascular surgery are rare but serious sequelae. They can occur in association with aortotomy, aortic cannulation sites, anastomotic suture lines, needle puncture sites, ^1,2 and broken wires. ³ Pseudoaneurysms of a prosthetic graft occur infrequently and are usually the result of a manufacturing defect. ⁴ To our knowledge, this is the 1st report of aortic graft pseudoaneurysms caused by fractured wires.

The exact incidence of sternal wire fracture after median sternotomy is unknown, but it is not rare. Wire fracture is attributed to mechanico-chemical cracking secondary to bending, twisting, and exposure to body fluids. ⁵ Sternal wound complications are also associated with diabetes, obesity, and chronic obstructive pulmonary disease. In our patient, the fractured wires may have been secondary to chronic coughing.

Six months before the patient presented with a pulsatile sternal mass, he had been clinically well with a stable sternum, although the CT scan taken at that time showed that the sternal wire had cut through the sternum and seemed loose. Our experience shows that the proximity of a foreign body to a pulsatile graft, such as the loosening sternal wire that impinged on the aortic graft in this patient, can lead to graft rupture and should prompt close follow-up by the treating physician. Early removal of loosening sternal wires, despite the stable condition of the sternum, might serve to avoid damage from the wires.

There are several options in the surgical management of the proximal ascending aorta during reoperation. ^1,2,5 The use of femoro-femoral bypass to cool the patient before opening the chest can facilitate the dissection and prevent excessive bleeding. However, when the core temperature is lowered in patients with aortic insufficiency, ventricular fibrillation can lead to ventricular distention and myocardial damage. ¹ In addition to the application of port-access technology to avoid such complications, ¹ we vented the left ventricular apex through a small left thoracotomy during the cooling period to prevent left ventricular distention. ² We found this technique to be easy, safe, and useful for preventing ventricular distention.