Radical surgery may not always be the answer for mycotic aneurysms

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By Martin Malina and Karolina Helczynska

It remains a widely accepted view that aortic infection with a primary mycotic (pseudo-) aneurysm or an infected aortic graft or stent graft should be treated radically. Radical treatment includes resection of the infected blood vessel and subsequent vascular reconstruction—extra anatomical, or possibly in situ.

Extensive vascular surgery is, however, poorly tolerated by compromised patients such as those with aortic infection. Early morbidity and mortality is significant and late complications include recurrent infection with haemorrhage. Blow out of the aortic stump exemplifies a feared complication of extra anatomical reconstruction. A less traumatic alternative treatment is, therefore, warranted.

We propose a “semi-conservative treatment” (SCT) of aortic infection (Helczynska K et al, Semi-Conservative Treatment of Mycotic Aortic Aneurysms and Graft Infections. In press). SCT is defined as drainage of the infected area, sometimes with debridement but without replacement of the aorta itself and without explanting an infected graft or stent graft. Mycotic or anastomotic pseudoaneurysms are bridged by stent graft, occasionally with adjunctive drainage of the sac. All patients receive long-term antibiotics.

Ninety two per cent (44) of the patients who presented with aortic infection at our institution were primarily treated with SCT during the last nine years. The median age of the patients was 70 years. One third had a primary mycotic pseudoaneurysm of the aorta, one third had an infected conventional graft and one third had an infected stent graft. Sixteen of the patients presented with a fistula to the intestine, oesophagus or bronchus.

Seven patients were treated with translumbar drainage of the aneurym sac, eight underwent open debridement of the sac and 23 received a stent graft. Positive cultures were obtained in 70% of the cases. Fifteen bacterial strains were identified, and six patients had mixed infections.

The 30-day mortality of SCT was 7%. Overall, infection-related mortality was 34% during a median follow-up of three years. The most favourable outcome of SCT, with a long-term survival of 85%, was obtained in patients treated for a primary mycotic pseudoaneurysm with stent graft. The least favourable results, with a mortality rate of 36%, occurred in aortoenteric fistulas.

Our most recent patient illustrates the potential advantage of SCT. This 62-year-old man presented with abdominal pain and sepsis. CT disclosed a rapidly expanding mycotic pseudoaneurysm of the abdominal aorta at the origin of the superior mesenteric artery (Figure 1). Traditional treatment would demand resection of the aorta and proximal superior mesenteric artery with either extra-anatomical bypass or in situ reconstruction. We treated the patient urgently with an off-the-shelf, tri-fenestrated stent graft with a scallop for the coeliac trunk. A proximal type I endoleak prompted us to extend the stent graft cranially across the coeliac trunk with a tubular stent graft that distally reached to the renal arteries. The overstented superior mesenteric artery was preserved with a reversed chimney graft (snorkel technique). Minor persisting opacification of the pseudoaneurysm was treated with direct translumbar injection of 1ml of thrombin. The patient was discharged on day three and has recovered fully. Follow-up CT shows patency of the superior mesenteric artery and renal arteries with resolution of the pseudoaneurysm. The patient’s CRP has dropped from 120 to 2 but he remains on antibiotics.

In conclusion, patients with aortic infection benefit from SCT with less surgical trauma as compared to radical surgery. This approach offers improved early survival and enhanced postoperative recovery while the long-term results seem at least similar to radical surgery. Further research is required to confirm these findings and explain why many patients heal while some do not. Patients with an aortoenteric fistula from a prosthetic graft still have a high mortality and morbidity.
 

Martin Malina and Karolina Helczynska are with the Vascular Center, Skane University Hospital, Malmö, Sweden

Figure 1. Rapidly expanding mycotic pseudoaneurysm of the aorta and proximal superior mesenteric artery. Sagital contrast enhanced CT reconstructions at one week (A) and one day before surgery (B), and at one week (C) and four months (D) after implantation of a complex stent graft. The mycotic pseudoaneurysm developed within days and was resorbed after complex EVAR with adjunctive injection of thrombin. Primary mycotic pseudoaneurysms seem to benefit from SCT the most with an 85% long term survival. 

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