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 can also begin at or above the renal arteries (suprarenal aneurysm). The missing or morphologically inadequate infrarenal anchoring zone („hostile neck“) excludes a conventional endovascular aneurysm exclusion.

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 proximalization 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 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
• paraanastomotic aneurysms after previous open aneurysm treatment

In the video example, it is a symptomatic abdominal aortic aneurysm with 9.5 cm diameter at the level of the renal arteries (juxtarenal), accompanying CAD, s/p pacemaker implantation right prepectoral:

Postoperative:

Because in interventional procedures, due to unexpected technical problems, a change in procedure to an open operation may become necessary, 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 with his 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
• Color duplex of the carotids (frequent coincidence of internal carotid stenoses)
• Echocardiogram
• Exercise ECG
• Laboratory investigations (electrolytes, coagulation, renal values, blood count, blood lipids)
• Chest X-ray
• if applicable, in the presence of concurrent PAD or critical visceral artery morphology, intra-arterial DSA of the abdominal aorta and pelvic and leg vessels
• Angio-CT of the thorax, abdomen, and pelvis to assess the vessels of the upper extremities and the descending aorta

• General OR Preparations
• Determine blood group, if necessary provide blood products
• 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 performed and is recommended by the German Society for Vascular Surgery (single-shot Cefuroxime 30 minutes before skin incision), however, the benefit is currently being discussed due to the resistance problem (RKI)   

General Surgical Risks

• Severe bleeding, blood transfusions, transmission of hepatitis/HIV through 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 hemostasis, 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 ischemia, amputation; surgical removal of the vascular prosthesis
• Stenosis and occlusion of the inserted chimney stents
• Damage to adjacent organs; Intestinal ischemia -> Resection, artificial anus placement
• Nerve lesions -> Sensory disturbances, pain, paralysis of the abdominal wall, thigh muscles
• Lymph fistula
• Lymphedema of the legs; temporary, permanent; compression stockings, lymphatic drainage
• Postoperative bleeding
• Impotence    
• Compromising renal function through intraoperative angiography, permanent dialysis

Risks due to Perfusion Disorders

• Thrombosis/Embolism: Pulmonary embolism, stroke, myocardial infarction; Prophylaxis Heparin-> HIT II risk
• Legs: Thrombosis of the vascular prosthesis and possibly adjacent vascular segments, possibly leg ischemia, amputation (e.g. toes)
• Kidneys: due to thrombosis or placement of the vascular prosthesis; Despite immediate surgical correction possibly permanent kidney damage -> Dialysis
• Intestine: Perfusion disorders due to thrombosis/embolism and possibly placement of the vascular prosthesis; Vascular surgical intervention required, possibly intestinal resection, permanent artificial anus
• 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 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 disorder due to hypoperfusion, especially in pre-existing liver diseases