Patients with tracheostomies are at risk for the formation of a fistulous tract between the trachea and the innominate artery. The incidence of tracheoinnominate artery fistula formation is thought to be between 0.1 and 1% of patients with a tracheostomy in place . The etiology of the tracheoinnominate artery fistula is considered to be multifactorial with factors ranging from pressure necrosis due to inflation of the cannula cuff, low tracheal incisions at the time of the index procedure, prolonged intubation, mucosal trauma from a malpositioned cannula tip, excessive neck extension or movement, and radiation therapy . Additional factors include episodes of hypotension, corticosteroid use, malnutrition, and infection . The fistula is often catastrophic because it carries an extremely poor prognosis. The majority of patients perish once the fistula forms. Even with immediate surgical intervention, more than 50% of patients do not survive, with another 56% of those who survive surgery expiring soon after surgery .
Surgical management of the tracheoinnominate artery fistula generally involves ligation of the tracheoinnominate artery, though some surgeons prefer to reconstruct the artery after resection of the fistula segment, since there is approximately a 10% risk of neurological sequelae, such as stroke, or other vascular complications in patients who have had ligation of the artery. However, it has been reported that there is also an increased risk of rebleeding in patients who have had reconstruction . Other surgeons have advocated preventative ligation of the innominate artery in patients who are at high risk for developing a tracheoinnominate artery fistula despite the increased risk for stroke at the time of tracheostomy . While there is currently no role for routine innominate artery flow assessment in patients who are status post a tracheostomy creation, Iodice et al. describe using computed axial tomography (CT) imaging to assess proximity of the innominate artery to the trachea in certain high-risk groups of patients. Those with impending tracheoinnominate artery fistula formation underwent epiaortic doppler and magnetic resonance arteriography to evaluate the presence of collateral circulation and to evaluate the risk of stroke in the setting of innominate artery ligation .
Bleeding in the operative field can greatly complicate life-saving intervention. For this reason, interventions which avoid the thorax can be appealing. Advances in endovascular surgery have provided another technique to manage a tracheoinnominate artery fistula. In certain select patients, an endovascular stent graft repair can be used as first-line treatment for management of the fistula and has been suggested as an option for bridging a patient with life-threatening bleeding until more formal surgical intervention can be performed .
Once the arterial component of the fistula is managed, either by resection or reconstruction, the tracheal defect must be repaired, especially in cases of arterial reconstruction. An autologous pericardial patch can be used . In some cases, bioprosthetic materials may need to be used to close the defect in the trachea. Udelsman et al. reported successfully using an aortic homograft and acellular dermal matrix for closure of other types of tracheal fistulae (e.g., tracheoesophageal fistulae) . Different vascular tissues such as a thoracic aortic patch, an abdominal aorta patch, and carotid patch with temporary stenting of the trachea have all been used successfully for repair of the tracheal defect. Microscopic analysis of biopsies taken from grafted tissue show metaplasia into well-differentiated tracheal tissue occurs after the trachea is repaired in this manner . The authors reported absence of mucous secretions or peristalsis, less immunogenicity, and less vascularity when using a vascular patch.
Flap procedures are frequently employed for repair of the tracheal defect. The most common flaps include sternocleidomastoid muscle flaps, deltopectoral flaps with costal cartridge, pectoralis major muscle flaps with costal cartilage, and chondromucosal forearm flaps . The use of a thymus flap, as was used in this case, has not previously been described in the setting of a tracheoinnominate artery fistula. The thymus has been used as a pedicled flap in repair of a tracheoesophageal fistula after primary repair for reinforcement, but after extensive literature review, only one published paper was identified in which the thymus had been utilized for closure of any tracheal defect, and this was for a controlled situation with a planned operation. In this case, a pedicled flap was created from the right lobe of the thymus and interposed into the tracheal defect . The thymus in our patient was an ideal structure to use as a pedicled flap. It was in close proximity to the trachea and did not require significant bending or twisting to approximate it over the defect which could have placed its blood supply at risk.
Emerging technologies have provided alternatives for reconstruction of tracheal defects. Over the last 15 years, tissue-engineered tracheal (TET) patches have been developed which are formed from a decellularized porcine jejunal scaffold seeded with muscle and fibroblasts. Since 2004, there have been a number of studies that have shown that once implanted, they are covered with respiratory epithelium and are virtually indistinguishable from native respiratory tissue . After the success of the jejunal scaffold, bioartificial materials have also been utilized, including 3D printed scaffolds that have been used to reconstruct large portions of the trachea. While these options have shown promise, they must be used in a pre-planned setting with extensive preoperative preparation.
Our patient eventually succumbed to toxic megacolon. Though it had nothing to do with the tracheoinnominate fistula, it deserves discussion. Toxic megacolon was first described in 1950 by Marschak et al. It occurs most commonly in the setting of Clostridium difficile colitis and ulcerative colitis and can progress to fulminant colitis which is almost invariably lethal if a colectomy is not performed .