Evidence - EVAR – Endovascular repair of abdominal aortic aneurysm (Y-graft) – Vascular Surgery - vascular surgery

By current reporting standards, an aneurysm is defined as a permanent localized dilation of artery having at least a 50% increase in diameter compared with the expected normal diameter. The mean transverse diameter of the infrarenal aorta in healthy males is about 1.93 cm and in females about 1.67 cm [1]. According to international consensus, a diameter of 3.0 cm or more is considered an abdominal aortic aneurysm (AAA).

Epidemiology and etiology

Accounting for 40–60% of cases, the most common location of aortic aneurysms is the abdominal aorta, with renal artery branches involved in 5% of patients.

Population-based studies demonstrated an AAA prevalence of 4–7.6% in men over 50 years of age and about 1.3% in women of the same age [2,3]. Hence, males are affected much more frequently in a ratio of 6:1. According to major international registry studies, perioperative all-cause mortality ranges from 1.6% for intact AAA (iAAA) to 31.6% for ruptured AAA (rAAA) [4]. With a mortality rate of up to 90%, the prognosis of rAAA is particularly poor, requiring effective strategies for elective management of iAAA [5].

The key risk factors in the development of AAA are smoking, positive family history; age; and atherosclerosis. Wth an odds ratio of 5.07, nicotine abuse constitutes the most significant risk factor [3].

Diagnostic work-up       

AAA is often diagnosed as an incidental finding during routine examinations or screening, and it is not uncommon for it to remain clinically silent until rupture. In the presence of a 3 cm AAA, clinical examination discovers the presence of AAA in only 29% of cases [6]. The gold standard in diagnostics and treatment planning of AAA is contrast-enhanced spiral computed tomography (sensitivity 93–100%, specificity up to 96%). Considering the high radiation dose delivered by CT (27.4 mSV in three phases, as compared to about 2 mSv for abdominal radiography), MRI studies are an equivalent option, especially in postoperative follow-up, with a sensitivity of 96% and specificity of up to 100% [7, 8]. Color-flow duplex ultrasonography with a sensitivity and specificity of up to 100%, depending on the experience of the operator may be an option in initial and screening studies of the abdominal aorta [9].

Management

In addition to conventional and pharmaceutical treatment for optimizing risk factors, invasive management of AAA includes open aortic repair (OAR) and endovascular aortic repair (EVAR). The approach should be tailored to each patient and take into account the patient's individual circumstances (underlying diseases, life expectancy, patient preferences).

Indication is always based on the present risk of rupture. This is less than 1% per year for AAA with a diameter of 4.4 cm and increases significantly in diameters 5 cm and more. For an AAA diameter of more than 5 cm, the annual risk of rupture is around 11% [10, 11]. In elective treatment of AAA, the individual risk of rupture must be compared with a 30-day mortality of about 1.8% for EVAR and 4.3% for OAR [12]. However, since the "early EVAR benefit" is lost in the long-run, both procedures offer an equivalent long-term outcome [13]. Therefore, the elective surgical risk in AAA <5 cm is higher than the annual rupture risk, and thus the indication for endoaneurysmorrhaphy is only true for diameters 5–5.5 cm and more. Since the annual growth rate of small aneurysms with a diameter <5 cm averages about 0.21 cm, follow-up by color-flow duplex ultrasonography should be performed at 6- or 12-month intervals [11, 14]. Complaints attributed to AAA and rapid progression in size beyond 0.5 cm in 6 months are associated with a significantly increased risk of rupture and therefore represent an absolute indication for surgery.

For a long time, endoaneurysmorrhaphy according to Creech constituted the standard treatment of AAA [15], for which coated  and uncoated straight and Y-grafts made of Dacron or PTFE are available. Three major randomized trials reported 30-day mortality as 3.0% (OVER, USA), 4.3% (EVAR-1, UK), and 4.6% (DREAM, Netherlands). Mortality, revision rate, and mortality are significantly lower when the procedure is performed in specialized vascular surgery centers: Perioperative mortality was about 2.2% for vascular surgeons, 4.0% for cardiac surgeons, and 5.5% for general surgeons. [16,17]. Cardiopulmonary complications; renal failure; bleeding complications; and infections are particularly important for perioperative mortality.

After the initial publication of the procedure in 1988 by Nikolay Volodos [18], EVAR procedures saw a steady rise worldwide. In 2010, the EVAR share was 74% in the United States [19] and about 73% in Germany in 2012 [20]. Whether EVAR is a viable option depends, among other factors, on the anatomy and morphology of the AAA and the access vessels. For challenging anatomical situations, customized endografts with fenestrations and branches, e.g., for the origins of the visceral arteries, are now available. Their use should be restricted to specialized centers, as mortality rate correlates significantly with the case volume [17, 21]

Assessment of the GORE® EXCLUDER® Conformable AAA Endoprosthesis In the Treatment of Abdominal Aortic Aneurysms (EXCeL)

Post Implantation Syndrome and Administration on NSAIDs in Patients Undergoing EVAR for AAA

Biomarker Profiling in Abdominal Aortic Aneurysm Patients (BIOMArCS-AAA)

Control Post Endovascular Treatment of Aortic Aneurisms Through Magnetic Resonance and Ultrasound (SAFEVAR)

Predictors of AAA Expansion and/or Rupture

Preferences for Open Vs. Endovascular Repair for Aortic Abdominal Aneurysm (PROVEE-AAA)

AAA Registry: Clinical Outcomes of Highly Angulated anatomY Treated With the Aorfix™ Stent Graft (ARCHYTAS)

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