By Dr Walid Mohabbat

Minimally invasive pure endovascular therapy is now feasible for complex aortic aneurysms including thoracoabdominal aortic aneurysms. Endovascular therapy using commercially available stentgrafts is frequently utilized to treat infrarenal abdominal aortic aneurysms (AAA). Large randomized trials have shown this minimally invasive technique to reduce the mortality rate associated with repair from ~5% with open surgery to ~1% with endovascular aneurysm repair (EVAR).

However, when the aortic repair involves the renal arteries or the visceral segment of the aorta, operative risks for open surgical repair are significantly higher with mortality rates of 10-30%. There are also more risks to consider including risks of renal ischaemic time leading to renal failure, bowel and hepatic ischaemia, as well as paralysis from spinal cord ischaemia. These risks are highest for patients that present with thoracoabdominal aortic aneurysms(TAAA).

Operative results for open repair of TAAA correlate with surgical volume of both the individual surgeon as well as the institution. In high volume open surgical centres in the USA, mortality rates range from a-b%. However, when the results all centres are pooled, the surgical outcomes are much more sobering. A state wide audit in the US state of California showed open TAAA had a perioperative 30 day mortality rate of d% and at 1 year post repair only g% of all patients were still alive.

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Thus, it is this group of patients with more complex aortic disease associated with very high perioperative morbidity and mortality from conventional open surgery that will derive the greatest benefit from endovascular therapy. Endovascular therapy has the potential to not only reduce the morbidity and mortality of aortic repair but also allows treatment of a large group of patients that were previously considered ‘inoperable’ or ‘too high a risk’.

Several centres from the United States and Europe have already reported promising early as well as midterm outcomes from this form of therapy for complex aortic disease.(REF) At the highest volume centre for endovascular therapy for complex aortic disease, the Cleveland Clinic, in Ohio, greater than 1200 aortic aneurysms are repaired annually. They began treating juxtarenal AAAs with fenestrated stent grafts in 1999 and have published midterm follow up data on their patients. Their results demonstrate that juxtarenal AAAs can be repaired with a mortality rate of e% at and TAAAs can be repaired with a mortality rate of d%. In follow-up the device is stable, d% of patients aneurysms continue to reduce in diameter, and renal and visceral complications are uncommon.

However it also clear that the intricacy and degree of complexity of designing and then implanting an aortic stent graft with branches to the coeliac, SMA, and renal arteries in the visceral segment or the subclavian and carotid arteries in the arch is several orders of magnitude higher than for infrarenal devices. Critical end organs depend on flow through the endoprosthesis being implanted and there is the potential for fatal complications. Thus the implanting surgeon is required to have specific subspecialty training in this field and should be proficient with planning, sizing, technical issues with implantation of aortic endografts, visceral and brachiocephalic artery stenting, and in troubleshooting for branched stentgrafts designs.

In conclusion, the entire aorta is within the domain of the aortic interventionalist. Today, there are no true contraindications to endovascular repair, instead it is the risk/benefit ratio of each possible treatment option that must be considered for individual patients. Patients with complex aortic disease have the most to gain from endovascular solutions. Surgeons who desire to implement these new technologies should ideally have subspecialty training in this field and be proficient with image interpretation, manipulation, endovascular grafting of the infrarenal aorta, and renal and mesenteric stenting prior to embarking on complex aortic procedures. Devices will become more complex and will be mated with additional small vessel stent grafts. However, clearly, the benefit of these technologies for this patient population are marked, and thus, as physicians, we must place great emphasis on the support of these technological developments and methods by which these skills can be disseminated.

by Dr Walid Mohabbat

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