CHICAGO – Successful management of infected aortic endovascular grafts requires careful operative planning and execution, meticulous postoperative care, and a fair bit of creativity.
“Each patient is different, so surgeons have to tailor the reconstructions to the individual patient and with these specific infections, have to be creative,” Dr. Thomas C. Bower, chair of vascular and endovascular surgery at Mayo Clinic, Rochester, Minn., said. “I’ve found the operations to be more challenging and more difficult than explanting portions or total graft excision when the infection has occurred in a hand-sewn graft.”
Unlike the typical bimodal distribution seen with hand-sewn graft infections, infection following endovascular repair of aortic aneurysms (EVAR) occurs from days up to 3 years after implantation. At the Mayo Clinic, a 79-year-old man presented with an infected endograft, psoas abscess, and Salmonella septicemia 4 years after EVAR.
“These infections are uncommon, but we are seeing more of them,” Dr. Bower said at a symposium on vascular surgery sponsored by Northwestern University.
Roughly two-thirds of patients will present with fever, nonspecific abdominal or back pain, malaise, weight loss or night sweats. If time permits, preoperative assessments include echocardiography for left ventricular function, arterial blood gases for pulmonary function since many patients are smokers, and renal ultrasound if creatinine is ≥ 1.5 mg/dL after rehydration. These tests are important because preoperative chronic obstructive pulmonary disease and renal dysfunction correlate with worse postoperative outcomes, he said.
Computed tomography angiography (CTA), however, stands as the single most important step of preoperative preparation, with the sine qua non of infection being air around the graft. Unlike hand-sewn grafts where infections can be localized, typically there is total graft involvement in these cases because the device is left inside the aneurysm sac. Aneurysms or pseudoaneurysms also have been seen above the infected device, including at the top end of suprarenal stents.
“This clearly has an impact on how we approach patients, but what’s become very apparent to me is that CTA often underestimates the amount of periaortic inflammation, especially at the juxta- and pararenal locations,” Dr. Bower said.
The Mayo group initially used in situ antibiotic-soaked prosthetic grafts for explanting EVAR devices, which yielded “acceptable mortality and reinfection rates, but primarily outstanding patency rates.” However, cryopreserved aortoiliac grafts have now become their first choice, Dr. Bower said. An ABO match is not imperative, preparation takes roughly 45 minutes, branch closures done in the lab are buttressed with sutures, and the graft is turned over to keep the lumbar arteries anterior, which offers an easy fix if there is bleeding, rather than having it on the posterior wall. Cryopreserved grafts, however, can dilate 40% and lengthen 10% under pressure.
“I’ve been burned more than once where the graft elongates more than I think, and I end up having to cut a small piece out to foreshorten it,” he said.
Reconstructions are tailored to patient anatomy. Surgeons should have several plans for reconstruction, including routing a graft through a remote path, remembering that CTA will underestimate the amount of periaortic inflammation. Separate bypasses of the renal or visceral arteries are performed first before the aortic clamp is applied to reduce physiologic stress. This requires knowledge of the supraceliac and pararenal aorta exposures, which really begins with the correct choice of incisions, Dr. Bower said. This is based on the aortic segment to be treated, position of the new graft, the aortic clamp site, and patient body habitus.
Most patients with EVAR infections are approached with a midline abdominal incision extended along the xiphoid process, which is the lynch pin for allowing upward and lateral retraction of the abdominal wall, he said. Choosing an incision that allows a more vertical orientation to where the new aortic anastomosis and clamp site will be, rather than operating in a keyhole, is important.
The second step is to open up the pararenal space by moving the viscera out of the way. This begins by ligating the inferior mesenteric vein and adjacent lymphatics, which allows incision of an avascular plane along the base of the left transverse colon. Retractor blades are set to allow the upward and lateral retraction of the small bowel, the left colon, and pancreas. Exposure of the suprarenal or supramesenteric aorta requires mobilization of the left renal vein after ligation and division of its branches.
“If that vein is intensely involved in inflammation, don’t ligate the branches in case you have to divide that vein at the caval confluence. Otherwise, you’ll run into some dysfunction of that left kidney,” Dr. Bower cautioned.