Perioperative management - Chimney technique for juxtarenal aortic aneurysm (Ch-EVAR)

Approximately 80% of abdominal aortic aneurysms are located infrarenally. However, in up to 20%, there is no sufficient aneurysm neck (juxtarenal aneurysm), and the AAA may also begin at or above the renal arteries (suprarenal aneurysm). The absent or morphologically inadequate infrarenal anchoring zone ("hostile neck") precludes conventional endovascular aneurysm repair.

Fenestrated prostheses or the chimney technique (Ch-EVAR = "chimney technique with endovascular aneurysm repair") allow these pathologies to be treated endovascularly. The chimney technique creates a proximalisation of the landing zone to ensure the necessary anchoring for the abdominal stent graft. This is achieved by implanting a usually covered stent (chimney graft) into the affected renovisceral vessel of the aorta, parallel to and outside the aortic endoprosthesis.

The indications for the treatment of pararenal pathologies using the chimney technique include:

• large rupture-prone aneurysms (> 6 cm diameter) or penetrating aortic ulcers without thrombus formation
• abdominal aneurysms with "hostile neck" and pronounced angulation/calcification of the iliac arteries and/or the aneurysm neck
• symptomatic, ruptured pathologies
• Type Ia endoleak after previous EVAR
• presence of relevant, accessory or ectopic renal arteries with a diameter of more than 4 mm
• para-anastomotic aneurysms after previous open aneurysm treatment

The video example shows a symptomatic abdominal aortic aneurysm with a diameter of 9.5 cm at the level of the renal arteries (juxtarenal), with accompanying CAD, and s/p pacemaker implantation right prepectorally:

Postoperatively:

Because in interventional procedures a conversion to open surgery may become necessary due 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 cancer

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 their relatives.

Thorough vascular surgical examination:

• Pulse status
• Doppler of the legs (frequent coincidence of popliteal aneurysms)
• If applicable, walking distance test in case of concurrent PAD and poorly palpable foot pulses
• Abdominal ultrasound
• Colour duplex of the carotid arteries (frequent coincidence of internal carotid artery stenoses)
• Echocardiogram
• Exercise ECG
• Laboratory investigations (electrolytes, coagulation, renal values, blood count, blood lipids)
• Chest X-ray
• if applicable, in the presence of concurrent PAOD or critical visceral artery morphology, intra-arterial DSA of the abdominal aorta and the pelvic and leg vessels
• Angio-CT of the thorax, abdomen and pelvis in order to assess the vessels of the upper extremities and the descending aorta

• General OR preparations
• Determine blood group, provide blood products if necessary
• Duplex sonography of the access vessels (A. brachialis, A. axillaris and, if necessary, A. subclavia on the access side)
• Fasting limit 6 hours
• Prophylactic antibiosis is usually administered and is recommended by the German Society for Vascular Surgery (single-shot cefuroxime 30 minutes before skin incision); however, the benefit is currently being debated owing to the problem of resistance (RKI)

General surgical risks

• Severe bleeding, blood transfusions, transmission of hepatitis/HIV through donor blood products
• Allergy/intolerance
• Wound infection
• Thrombosis/embolism
• Skin, vascular, and 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
• 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
• Stenosis and occlusion of the inserted chimney stents
• Damage to adjacent organs; intestinal ischaemia -> resection, creation of a stoma
• Nerve lesions -> dysaesthesia, pain, paralysis of the abdominal wall and thigh musculature
• Lymphatic fistula
• Lymphoedema of the legs; temporary, permanent; compression stockings, lymphatic drainage
• Postoperative rebleeding
• Impotence
• Compromise of renal function due to intraoperative angiography, permanent dialysis

Risks due to perfusion disorders

• Thrombosis/embolism: pulmonary embolism, stroke, myocardial infarction; prophylaxis with heparin -> risk of HIT II
• 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/paresis, possibly also permanent paraplegia in case of a low-originating A. radicularis magna
• Gluteal musculature: 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 disease