Perioperative management - Endovascular bifurcation prosthesis for infrarenal AAA with simultaneous aneurysm of the right common iliac artery (EVAR with iliac side branch)

• Abdominal aortic aneurysm (AAA) > 5 cm
• smaller aneurysms in eccentric AAA or ulcerations with contained perforation (PAU, penetrating aortic ulcer)
• symptomatic aneurysms of any size

Special indications and treatment options in Behçet's disease, Marfan syndrome, mycotic aneurysms such as Salmonella infections, and AAA with peripheral embolisation.

The indication for invasive treatment of an abdominal aortic aneurysm (AAA) is fundamentally based on weighing the individual rupture risk in the natural course against the operative risk. If the rupture risk in the natural course exceeds the individual operative risk, the indication for invasive treatment is generally made.

Classification of rupture risk

Surgical indication

Two procedures are available for the surgical treatment of AAA:

• open replacement of the abdominal aorta with a tube or bifurcation prosthesis (OAR, open aortic repair)
• endovascular implantation of a stent prosthesis (EVAR, endovascular aortic repair)

Laparoscopic aneurysm surgery, usually in combination with a mini-laparotomy, is of rather minor importance.

The following recommendations exist for selecting the procedure – OAR or EVAR:

OAR (trans-, retroperitoneal)

• normal life expectancy
• low surgical risk (“fitness”)
• anatomy unsuitable for EVAR: landing zone, aneurysm neck (angle, length), iliac vessels (stenoses, elongation, kinking), thrombi, calcification
• Marfan and other connective tissue diseases

EVAR (standard prosthesis, custom-made)

• previous abdominal operations
• limited life expectancy
• high surgical risk
• anatomy suitable for EVAR (see above)

EVAR requires adequate iliac vessels for access, as the stent graft systems are often large-calibre. Atherosclerotically narrowed, tortuous and kinked, but also aneurysmatically dilated iliac vessels are problematic.

In the long-term course, the endovascular aortic prosthesis is associated with a higher complication rate than open aortic surgery.

The mortality risk for EVAR or OAR of an individual patient can be quickly calculated using the so-called BAR Score Calculator → www.britishaneurysmrepairscore.com, which can be usefully employed for patient counselling about the risk of an elective procedure with EVAR or OAR.

The general surgical indication for an (isolated) iliac aneurysm is given from an aneurysm diameter of 3 cm.

Video example:

• infrarenal AAA, diameter 54.2 mm
• aneurysm of the right common iliac artery, diameter 41.1 mm

Because in an interventional approach a change of procedure to open surgery may become necessary owing to unexpected technical problems, preoperative risk assessment and the definition of contraindications are important:

• Heart failure (ejection fraction < 25-30 %)
• COPD (FEV1 < 0.8)
• non-correctable severe CAD
• incurable malignancy

Relative contraindication:

• compensated renal insufficiency (due to intraoperative contrast medium load)

If in borderline cases the operation is to be performed despite contraindications, this requires special agreement with the patient or with their relatives.

Technical contraindications for endovascular treatment: see Preoperative Diagnostics/Planning

Thorough vascular surgical examination:

• Pulse status
• Doppler of the legs
• if necessary, walking distance test in case of concurrent PAD and poorly palpable foot pulses
• Abdominal ultrasound
• Colour duplex of the carotids
• Echocardiography
• Stress ECG
• Laboratory tests (electrolytes, coagulation, renal values, blood count, blood lipids)
• Chest X-ray
• Spiral CT
• if necessary, in case of concurrent PAD or critical visceral artery morphology, i.a. DSA of the abdominal aorta and the pelvic and leg vessels

Of particular importance is the preoperative angiographic clarification of the access pathology:

• Stenoses of the femoral and pelvic arteries
• Aneurysms of the access arteries
• local infections such as e.g. erythrasma
• Previous operations in the surgical area

A special feature is the presence of a horseshoe kidney in AAA, where special planning is necessary both in a planned open procedure and in an endovascular procedure, which must take into account the preservation of the multiple renal arteries in the area of the abdominal aortic aneurysm.

In summary, the preoperative diagnostics must therefore consider the following parameters:

1. Aortic pathology

2. Risk factors (multimorbidity)

3. Access pathology

Planning

In this context, the measurement of the aneurysm and the consideration of calcifications and stenoses are of decisive importance in order to assess local feasibility.

One of the possible contraindications to endovascular treatment is severe kinking of the aneurysm neck. Furthermore, coiling, compression and elongation must be taken into account, because the prosthesis – depending on the centreline – may deviate from the aneurysm configuration and consequently lead to misplacements.

When measuring, the exact guidelines of the prosthesis manufacturer must be observed. These differ depending on the type of prosthesis. For example, oversizing of the iliac prosthesis should be between 7 and 35 %. Each manufacturer has its own case planning forms and its particular guidelines regarding minimum lengths, diameters, oversizing, minimum overlaps, etc. The recommended accessories can also vary depending on the prosthesis manufacturer and must be strictly observed.

• Determine blood type, provide blood products if necessary
• Depilate the surgical area
• if necessary, insert urinary catheter
• Prophylactic antibiosis is usually performed and is recommended by the German Society for Vascular Surgery (single-shot Cefuroxime 30 minutes before skin incision); however, its benefit is currently being debated owing to the resistance problem (RKI).

General Surgical Risks

• Severe bleeding, blood transfusions, transmission of Hepatitis/HIV through donor blood products
• Allergy/Intolerance
• Wound infection
• Thrombosis/Embolism
• Skin, vascular, nerve damage e.g. due to positioning
• Keloids (if open access)

Specific Procedure Risks

• Vascular injuries e.g. during prosthesis placement: surgical haemostasis, blood transfusions, in case of severe bleeding or aortic tear immediate conversion to open surgery
• Pseudoaneurysm of the punctured vessels, AV fistula, seroma
• Primary aortoenteric fistula: surgical intervention, possibly with removal of the vascular prosthesis
• Inadequate anchoring or leakage of the prosthesis: corrective procedures, possibly open
• Infection of the vascular prosthesis: possible after days, months or years; endocarditis, sepsis, leg ischaemia, amputation; surgical removal of the vascular prosthesis
• Damage to adjacent organs; intestinal ischaemia → resection, stoma placement
• Nerve lesions → sensory disturbances, pain, paralysis of the abdominal wall and thigh muscles
• Lymph fistula
• Lymphoedema of the legs; temporary, permanent; compression stockings, lymphatic drainage
• Postoperative bleeding
• Impotence
• Compromised renal function due to intraoperative angiography, permanent dialysis

Risks from perfusion disorders

• Thrombosis/embolism: pulmonary embolism, stroke, myocardial infarction; prophylaxis with heparin → HIT II risk
• Legs: thrombosis of the vascular prosthesis and possibly adjacent vascular segments, possibly leg ischaemia, amputation (e.g. toes)
• Kidneys: due to thrombosis or placement of the vascular prosthesis; despite immediate surgical correction, possibly permanent renal damage → dialysis
• Intestine: perfusion disorders due to thrombosis/embolism and possibly placement of the vascular prosthesis; vascular surgical intervention required, possibly intestinal resection, permanent stoma
• Spinal cord: depending on the size of the aneurysm, perfusion disorders due to placement of the vascular prosthesis; temporary sensory disturbances/pareses, possibly also permanent paraplegia in case of a low-originating A. radicularis magna
• Gluteal muscles: due to overstenting of the pelvic arteries, especially bilaterally; claudication symptoms when walking, possibly gluteal necrosis formation
• Liver: functional impairment due to hypoperfusion, especially in pre-existing liver conditions