ANZ J. Surg.

2002;

72

: 908–909

CONTINUING MEDICAL EDUCATION

Continuing Medical Education

ENDOVASCULAR REPAIR OF ABDOMINAL AORTIC ANEURYSM: AN UPDATE

J

AMES

M

AY

Department of Surgery, University of Sydney, New South Wales, Australia

Key words: abdominal aortic aneurysm, endovascular repair, open repair.

Abbreviation

: AAA, abdominal aortic aneurysm.

INTRODUCTION

This paper is written for surgeons who are unfamiliar with, orwould like an update on, the endovascular method of repairingabdominal aortic aneurysm (AAA). A number of questions canbe anticipated from surgeons within these two groups: what isendovascular repair?; how does it work?; can all AAAs be treatedby this method?; what are the advantages?; what are the dis-advantages?; how does endovascular repair compare with con-ventional open repair of AAA?; what are the current guidelinesfor operating on patients with AAA?; should I refer patients forendovascular treatment or open repair? Answers to these ques-tions should provide a balanced and current view on the place ofendovascular repair of AAA.

THE ENDOVASCULAR METHOD IS A MEANS OF REPAIRING AN ANEURYSM FROM WITHIN

THE ARTERY

Endovascular AAA repair involves the transfemoral placement,through a small incision in the groin, of an endograft within theaneurysm. The endograft is introduced by means of a low-profilecatheter and anchored in place by a self-expanding metal framewhich supports all or part of the fabric of the endograft. The graftprovides a blood-tight seal proximal and distal to the weakenedand dilated segment of the aorta and completely excludes theaneurysm sac from the general circulation.

CAN ALL ABDOMINAL AORTIC ANEURYSMS BE TREATED BY THIS METHOD?

Not all AAAs are anatomically suitable for endovascular repair.The major determinant in deciding suitability is the proximalneck of the aneurysm. A collar of normal aorta between the renalarteries and the aneurysm (at least 15 mm long and 28 mm or lessin diameter) is required. Tortuosity and heavy circumferentialcalcification in the iliac arteries may also preclude the technique.The cost of the prostheses (at approximately $10 000) may alsobe a limiting factor.

WHAT ARE THE ADVANTAGES OF ENDOVASCULAR REPAIR OF ABDOMINAL

AORTIC ANEURYSM?

Because it avoids the need for laparotomy, cross-clamping ofthe aorta and the obligatory blood loss associated with openingthe aneurysm sac, the technique has much to recommend it. Ithas the potential to reduce the morbidity and mortality associatedwith conventional open AAA repair, and to extend the scope ofrepair to those patients with severe medical comorbidities whowere previously denied treatment.

WHAT ARE THE DISADVANTAGES?

There are some limitations with the endovascular method. One isthe unknown long-term outcome and, specifically, whether thedeployment of an endograft in the proximal neck of the AAA willarrest the natural history of progressive aneurysm degeneration inthat segment of the aorta. Similarly, the durability of the pros-theses in the long term is unknown; structural failure in somecases has already been reported in the majority of devices within4 years of insertion.

1

Another limitation unique to endovascularrepair is the potential for endoleak, or incomplete exclusion of theaneurysm sac, where a leakage remains within the artery butexternal to the endograft. The potential for this complicationmakes annual review with computed tomography or ultrasonog-raphy mandatory. Endoleaks, however, are treatable by second-ary endovascular repair.

2

Approximately 10% of patients whoundergo endovascular repair require this secondary intervention.

2

HOW DOES ENDOVASCULAR REPAIR COMPARE WITH CONVENTIONAL OPEN REPAIR OF

ABDOMINAL AORTIC ANEURYSM?

There are currently no reports of a prospective, randomized con-current comparison of the two methods. There are three reports ofconcurrent comparison of the two methods.

3–5

In all three reports,failure to cure the aneurysm was significantly higher in theendovascular group compared with the open group. In the mostrecent of the three studies, however, the perioperative mortalityrate for endovascular repair was 2.7% compared with 6.8% foropen repair. Survival at 4 years was also significantly better in theendovascular group compared with the open group. This superiorsurvival was achieved despite 31% of the endovascular groupbeing classified as high risk and unfit for open repair. Blood lossat operation, the need for intensive care and duration of hospitalstay were also significantly decreased in the endovascular group.

J. May,

AC, MD, FRACS.

Correspondence: J. May, Department of Surgery, University of SydneyD06, NSW 2006, Australia.Email: vascsurg@med.usyd.edu.au

Accepted for publication 21 August 2002.

ENDOVASCULAR REPAIR 909

WHAT ARE THE CURRENT GUIDELINES FOR OPERATING ON PATIENTS WITH ABDOMINAL

AORTIC ANEURYSM?

The indications for AAA repair include asymptomatic aneurysmsmore than 5 cm in diameter, and all symptomatic and rupturedaneurysms, provided coexisting medical conditions do not pre-clude operation.

6

Although aneurysms less than 5 cm in diametercan rupture, the risk is of the order of 1%. Ultrasound remains anappropriate method of determining the presence and size ofAAAs.

SHOULD I REFER PATIENTS FOR ENDOVASCULAR OR OPEN REPAIR?

An assessment of the patient’s cardiovascular, respiratory andrenal status may well settle this issue, as many patients are unfitfor open repair due to medical comorbidities. These patients

benefit from endovascular repair provided they are anatomicallysuitable. The preferred investigation for determining suitability isa contrast enhanced computed tomography scan of the abdominalaorta with magnified views and 0.5-cm cuts between the renalarteries and bifurcation of the common iliac arteries.

For patients who are anatomically suitable for endovascularrepair and fit to undergo either endovascular or open repair, thechoice is controversial. Endovascular repair allows AAAs to berepaired less invasively, with lower perioperative mortality andbetter survival compared with conventional open repair. Theseadvantages must be weighed against the disadvantages of theneed for lifelong surveillance, the possibility of secondary inter-vention being required for graft failure and the small risk ofunpredicted rupture.

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ACKNOWLEDGEMENT

Some of the material for this paper has been taken from an Edit-orial in the

Medical Journal of Australia

.

8

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Author:

James May.