Endovascular aneurysm repair
Encyclopedia
EVAR which stands for Endovascular Aneurysm Repair (or Endovascular Aortic Repair), is a type of Endovascular surgery
used to treat an abdominal aortic aneurysm
(AAA) or Thoracic Aortic Aneurysm, the procedure then specifically termed TEVAR (Thoracic Endovascular Aortic/Aneurysm Repair). In certain occasions, a specially designed Custom-made graft device, which has holes(fenestrations) on the graft body to maintain the patency of certain important blood vessels, is used for the procedure, which is called FEVAR (Fenestrated EndoVascular Aortic/Aneurysm Repair).
and introduced in an article written in 1988. In Argentina
it was first introduced in 1991 by Juan Parodi and the very same year in the USA by Michael Dake.
The procedure is carried out in a sterile environment, usually a theatre, under x-ray fluoroscopic guidance. It is carried out by an Interventional Radiologist or vascular surgeon. The patient is either given a full GA (general anaestheic) or regional anaesthesia.
Vascular 'sheaths' are introduced into the patient's femoral arteries, through which the guidewires, catheters and eventually, the Stent Graft is passed.
Diagnostic angiography images or 'runs' are captured of the aorta to determine the location on the patient's renal arteries, so the stent graft can be deployed without blocking these. Failure to achieve this will cause renal failure, thus the precision and control of the graft stent deployment is extremely important. The main 'body' of the stent graft is placed first, follow by the 'limbs' which join on to the main body and sit on the Aortic Bifurcation for better support, and extend to the Iliac arteries.
For certain occasions that the aneurysm extends down to the Common Iliac Arteries, a specially designed graft stent, named as Iliac Branch Device (IBD), can be used, instead of blocking the Internal Iliac Arteries, but preserve them. The preservation of the Internal Iliac Arteries is important to prevent Buttock Claudication, and to preserve the full genital functions.
The idea is that the stent graft (covered stent), once in place acts as an artificial lumen for blood to flow down, and not into the surrounding aneurysm sac. This therefore immediately takes the pressure off the aneurysm wall, which itself will thrombose in time.
A newer adaption of EVAR is the Hybrid Procedure. A hybrid procedure occurs in the angiography room and aims to combine endovascular procedures with limited open surgery. In this procedure the stent graft deployment is planned to combine with an open operation to revascularise selected arteries that will be "covered" by the stent graft i.e. deprived of arterial inflow. In this method more extensive EVAR devices can be deployed to treat the primary lesion while preserving arterial flow to critical arteries.
Thoraco-abdominal aneurysms (TAA) typically involve such vessels and deployment of the EVAR device will cover important arteries e.g. visceral or renal arteries, resulting in end organ ischaemia which may not be survivable. The open operation component aims to bring a bypass graft from an artery outside the stent graft coverage to vital arteries within the coverage region. This component adds to the EVAR procedure in time and risk but is usually judged to be lesser that the risk of the major totally open operation.
Staging such procedures is common. A common example is revascularisation of the left common carotid artery and/or the left subclavian artery from the innominate artery or the right common carotid artery to allow treatment of a thoracic aortic aneurysm that encroachs proximally into the aortic arch to be treated without thoracotomy. Continued design improvement in stent graft including branched endografts will reduce but not eliminate this category of surgery. 'Chimney stents into the innominate artery with TEVAR into the proximal aortic arch have recently been described. Other surgeons favor limited thoracotomy with carotid-carotid bypass i.e. hybrid procedures.
All such procedures aim to reduce the morbidity and mortality of treating arterial disease in a patient polpulation that is increasingly older and less fit than when major open repairs were developed and popluarised. Even in those days, significant risks were accepted in the understanding than the large open operation was the only option. that so not the case in most patients today. durability and problems such as 'endoleaks' may require careful surveillance and adjuvant procedures to ensure success of the EVAR or EVAR/hybid procedure. CT Angiography (CTA) imaging has in particular made a key contribution to planning, success, durabity in this complex area of vascular surgery.
, groin hematoma
, wound infection
, TEVAR does not seem either improve or compromise 2-year survival and adverse event rates. Its use in complicated aortic dissection
is under investigation.
Endovascular surgery
Endovascular surgery is a form of minimally invasive surgery that was designed to access many regions of the body via major blood vessels.Endovascular techniques were originally designed for diagnostic purposes. Basic techniques involve the introduction of a catheter percutaneously into a large...
used to treat an abdominal aortic aneurysm
Abdominal aortic aneurysm
Abdominal aortic aneurysm is a localized dilatation of the abdominal aorta exceeding the normal diameter by more than 50 percent, and is the most common form of aortic aneurysm...
(AAA) or Thoracic Aortic Aneurysm, the procedure then specifically termed TEVAR (Thoracic Endovascular Aortic/Aneurysm Repair). In certain occasions, a specially designed Custom-made graft device, which has holes(fenestrations) on the graft body to maintain the patency of certain important blood vessels, is used for the procedure, which is called FEVAR (Fenestrated EndoVascular Aortic/Aneurysm Repair).
History
The world's first EVAR was performed in 1987 by Nicholas Volodos in Kharkov, Soviet UnionSoviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
and introduced in an article written in 1988. In Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
it was first introduced in 1991 by Juan Parodi and the very same year in the USA by Michael Dake.
Patient screening
Before patients are deemed to be a suitable candidate for this treatment, they have to go through a rigorous set of tests. These include a CT scan of the complete thorax/abdomen/pelvis, and blood tests. The CT scan gives precise measurements of the aneurysm and the surrounding anatomy. In particular the calibre/tortuosity of the iliac arteries and the relationship of the neck of the aneurysm to the renal arteries are important determinants of whether the aneurysm is amenable to endoluminal repair. In certain occasions that the renal arteries are too close to the aneurysm, the custom-made fenestrated graft stent is now another way out than doing open surgery.The procedure
Vascular 'sheaths' are introduced into the patient's femoral arteries, through which the guidewires, catheters and eventually, the Stent Graft is passed.
Diagnostic angiography images or 'runs' are captured of the aorta to determine the location on the patient's renal arteries, so the stent graft can be deployed without blocking these. Failure to achieve this will cause renal failure, thus the precision and control of the graft stent deployment is extremely important. The main 'body' of the stent graft is placed first, follow by the 'limbs' which join on to the main body and sit on the Aortic Bifurcation for better support, and extend to the Iliac arteries.
For certain occasions that the aneurysm extends down to the Common Iliac Arteries, a specially designed graft stent, named as Iliac Branch Device (IBD), can be used, instead of blocking the Internal Iliac Arteries, but preserve them. The preservation of the Internal Iliac Arteries is important to prevent Buttock Claudication, and to preserve the full genital functions.
The idea is that the stent graft (covered stent), once in place acts as an artificial lumen for blood to flow down, and not into the surrounding aneurysm sac. This therefore immediately takes the pressure off the aneurysm wall, which itself will thrombose in time.
Thoraco-abdominal aneurysms (TAA) typically involve such vessels and deployment of the EVAR device will cover important arteries e.g. visceral or renal arteries, resulting in end organ ischaemia which may not be survivable. The open operation component aims to bring a bypass graft from an artery outside the stent graft coverage to vital arteries within the coverage region. This component adds to the EVAR procedure in time and risk but is usually judged to be lesser that the risk of the major totally open operation.
Staging such procedures is common. A common example is revascularisation of the left common carotid artery and/or the left subclavian artery from the innominate artery or the right common carotid artery to allow treatment of a thoracic aortic aneurysm that encroachs proximally into the aortic arch to be treated without thoracotomy. Continued design improvement in stent graft including branched endografts will reduce but not eliminate this category of surgery. 'Chimney stents into the innominate artery with TEVAR into the proximal aortic arch have recently been described. Other surgeons favor limited thoracotomy with carotid-carotid bypass i.e. hybrid procedures.
All such procedures aim to reduce the morbidity and mortality of treating arterial disease in a patient polpulation that is increasingly older and less fit than when major open repairs were developed and popluarised. Even in those days, significant risks were accepted in the understanding than the large open operation was the only option. that so not the case in most patients today. durability and problems such as 'endoleaks' may require careful surveillance and adjuvant procedures to ensure success of the EVAR or EVAR/hybid procedure. CT Angiography (CTA) imaging has in particular made a key contribution to planning, success, durabity in this complex area of vascular surgery.
Systemic
Myocardial infarction, congestive heart failure, arrhythmias, respiratory failure, renal failureRenal failure
Renal failure or kidney failure describes a medical condition in which the kidneys fail to adequately filter toxins and waste products from the blood...
Procedure related
Dissection, malpositioning, renal failure, thromboembolizaton, ischemic colitisIschemic colitis
Ischemic colitis is a medical condition in which inflammation and injury of the large intestine result from inadequate blood supply. Although uncommon in the general population, ischemic colitis occurs with greater frequency in the elderly, and is the most common form of bowel ischemia...
, groin hematoma
Hematoma
A hematoma, or haematoma, is a localized collection of blood outside the blood vessels, usually in liquid form within the tissue. This distinguishes it from an ecchymosis, which is the spread of blood under the skin in a thin layer, commonly called a bruise...
, wound infection
Endoleaks
An endoleak is a leak into the aneurysm sac after endovascular repair. Five types of endoleaks exist:- Type I - Perigraft leakage at proximal or distal graft attachment sites (near the renal and iliac arteries)
- Type II - Retrograde flow from collateral branches such as the lumbar, testicularTesticular arteryThe testicular artery is a branch of the abdominal aorta that supplies blood to the testis. It is a paired artery, with one for each of the testes....
and inferior mesenteric arteriesInferior mesenteric arteryIn human anatomy, the inferior mesenteric artery, often abbreviated as IMA, supplies the large intestine from the left colic flexure to the upper part of the rectum, which includes the descending colon, the sigmoid colon, and part of the rectum... - Type III - Leakage between different parts of the stent (at the anastomosis between components)
- Type IV - Leakage through the graft wall due to the quality of the graft material
- Type V - Leakage from unknown origin
Use in aortic dissection
In uncomplicated type B aortic dissectionAortic dissection
Aortic dissection occurs when a tear in the inner wall of the aorta causes blood to flow between the layers of the wall of the aorta and force the layers apart. The dissection typically extends anterograde, but can extend retrograde from the site of the intimal tear. Aortic dissection is a medical...
, TEVAR does not seem either improve or compromise 2-year survival and adverse event rates. Its use in complicated aortic dissection
Aortic dissection
Aortic dissection occurs when a tear in the inner wall of the aorta causes blood to flow between the layers of the wall of the aorta and force the layers apart. The dissection typically extends anterograde, but can extend retrograde from the site of the intimal tear. Aortic dissection is a medical...
is under investigation.