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Abdominal Aortic Aneurysm — Open versus Endovascular Repair

Abdominal Aortic Aneurysm — Open versus Endovascular Repair

Abdominal Aortic Aneurysm — Open versus Endovascular Repair
Frank A. Lederle, M.D.
The publication in this issue of the
Journal
of the
Dutch Randomized Endovascular Aneurysm Management
(DREAM) trial
1
and the recent publication
of a similar study from the United Kingdom
2
provide
the first randomized comparisons of the endovascular
and open techniques for elective repair
of abdominal aortic aneurysms. Elective repair is
undertaken to prevent the rupture of aneurysms,
which carries a mortality rate of about 80 percent.
More than 40,000 procedures are performed each
year in the United States. Open surgical repair, in
which the aneurysm is opened and a graft sewn into
place under direct vision, has proved durable in both
senses: it has been in use for more than 50 years,
and the rate of graft failure is only about 0.3 percent
per year.
3-5
It is, however, major surgery performed
in frail, elderly patients with a high rate of
complications, a mortality rate that is not negligible,
and a recovery time of several months.
Endovascular repair was developed to provide
a less traumatic alternative. Endovascular grafts are
positioned inside the aneurysm under radiologic
guidance and secured with hooks or pressure to
shield the segment containing the aneurysm from
the blood pressure. The advent of endovascular repair
has not been without controversy. After deciding
to accept nonrandomized studies of effectiveness,
the Food and Drug Administration (FDA)
approved two graft systems in 1999, one of which
was subsequently withdrawn, and has approved two
more since then. Though endovascular repair has
been extolled by many as the wave of the future, its
brief but clamorous history has also been marked
by FDA warnings and allegations of fraud, an editorial
denouncing the procedure
6
as a “failed experiment,”
and most recently, industry threats of legal
action to block publication of an unfavorable
FDA report.
7
Nearly all studies have found that, as compared
with open repair, endovascular repair results in reduced
rates of operative morbidity, a shorter initial
hospital stay, and shorter recovery time. Somewhat
surprising, though, is that early studies found no
improvement in operative mortality rates. That this
has changed can be seen most dramatically in statewide
data from New York over three years.
8
In 2000,
the rate of operative mortality for endovascular repair
(3.1 percent) was similar to that for open repair
(4.1 percent), but during the next two years,
while the mortality rate associated with open repair
remained unchanged, the rate for endovascular
repair dropped to 1 percent. These rates were confirmed
by a study of the 2001 Nationwide Inpatient
Sample,
9
which reported rates of operative mortality
of 3.8 percent for open repair and 1.3 percent
for endovascular repair.
Nevertheless, even large population-based observational
studies can be biased by differences between
treatment groups. Elective open repair is not
offered to patients at high risk for operative complications,
and endovascular repair is limited to patients
who have a suitable segment of normal aorta
below the renal arteries and who also have iliac arteries
free of excessive plaque or tortuosity. Since
the resulting differences between treatment groups
could obviously affect outcomes, the reports from
the two new randomized trials are welcome additions.
The DREAM trial investigators observed substantial
reductions in the primary outcome of operative
(30-day) morbidity and mortality with endovascular
repair, as compared with open repair,
that did not reach statistical significance owing to
the relatively small sample size. The reduction in
operative mortality with endovascular repair in the
DREAM trial, from 4.6 percent to 1.2 percent, was
very similar to the findings of the larger trial in the
United Kingdom.
2
That study, the Endovascular

Aneurysm Repair (EVAR) trial, randomized 1082
patients and reported a significant reduction in
operative mortality with endovascular versus open
repair, from 4.7 percent to 1.7 percent. The remarkable
agreement among the two population-based
observational studies and the two trials leaves little
doubt that endovascular repair is now associated
with reduced rates of operative mortality and morbidity
and a shorter initial hospital stay as compared
with the rates for open repair.
Should we then accept the conclusion of the
DREAM authors that “endovascular repair is preferable
to open repair”? I believe we should not, because
operative morbidity and mortality rates represent
only half the equation; they address the risk
associated with repair, but not the benefit. The more
innocuous therapy is favored in a comparison of
procedural complications, even if that therapy is ineffective.
Just as we would not compare angioplasty
and coronary bypass without considering subsequent
cardiac events, we cannot compare open repair
with endovascular repair without evaluating
the long-term risk of aneurysm rupture and graft
complications. There is reason to be cautious in this
arena. Two large European registries have reported
a failure rate for endovascular grafts of 3 percent
per year (1 percent for rupture plus 2 percent for
conversion to open repair), which is 10 times the
failure rate of 0.3 percent for open repair, noted
above, and a total secondary-intervention rate of
10 percent per year.
10-12
Although potentially biased
by substantial losses to follow-up, these registries
are probably the best source available. The
conclusion of the suppressed FDA report was that
the total aneurysm-related mortality rate will probably
be higher with endovascular repair than with
open repair when late deaths are included.
7
The late complications after endovascular repair
have other important implications, such as the universal
requirement for follow-up computed tomography
each year for the rest of the patient’s life —
which is proving to be a considerable burden for
both patients and physicians. Another may be the
loss within one year of the initial advantage over
open repair in the total number of days spent in
the hospital.
13
Recent reports from one of the
registries
14
and from the Cleveland Clinic
15
raise yet
another concern: long-term results after endovascular
repair appear to be much worse for larger
aneurysms, the ones most in need of repair. The
four-year postoperative rupture rate in the registry
study
14
was 10 percent for abdominal aortic aneurysms
measuring 6.5 cm or more in diameter at the
time of endovascular repair, as compared with 2 percent
for smaller aneurysms. Two years after endovascular
repair in the Cleveland series, 6.1 percent
of patients with abdominal aortic aneurysms that
measured 5.5 cm or larger had aneurysm-related
deaths, and 8.2 percent required conversion to open
repair, as compared with 1.5 percent and 1.4 percent,
respectively, of those with aneurysms measuring
less than 5.5 cm.
15
These findings are of particular concern because
the aspect of the management of abdominal
aortic aneurysms for which there is the most certainty,
on the basis of results of two large trials,
5,16
is the lack of benefit from repair of aneurysms
smaller than 5.5 cm. Because the rupture rate of
abdominal aortic aneurysms smaller than 5.5 cm
that were followed with imaging surveillance was
no more than 1 percent per year in those trials, it is
unlikely that any treatment will be proved significantly
better than surveillance for these patients.
Nevertheless, the enthusiasm (aided by marketing
and turf battles) surrounding endovascular repair
has increased the temptation to repair smaller aneurysms.
Forty-five percent of the registry patients
and nearly 60 percent of the Cleveland patients who
were treated with endovascular repair had aneurysms
smaller than 5.5 cm.
14,15
No comparison of treatments can be complete
without consideration of cost. Despite the reduced
rate of operative morbidity and the shorter hospital
stay, numerous studies have found endovascular
repair to be more expensive than open repair, primarily
because of the high price of the grafts (about
$13,000 per patient). The extra cost attributable to
the use of endovascular repair in place of open repair
in the United States in 2001 alone has been estimated
at more than $50 million.
9
The authors of the EVAR trial wisely advise us
that the new findings should be considered “a license
to continue scientific evaluation of [endovascular
repair], but not to change clinical practice”
until evidence from trials is available for long-term
outcomes.
2
The EVAR trial should provide a first
look at this evidence as early as next year, with more
evidence to follow from the DREAM trial, the Veterans
Affairs Open versus Endovascular Repair
(OVER) trial, and the French Anévrisme de l’aorte
abdominale: Chirurgie versus Endoprothèse (ACE)
trial. Even if these trials show endovascular repair
to be superior after several years of follow-up, the
best treatment for younger patients will remain
editorials
1679
uncertain until we know how endovascular repair
fares over decades. In addition, “small incision” and
laparoscopic techniques have been developed, and
further studies will be needed to clarify their roles.
Meanwhile, patient management should be
guided by what we already know. Small aneurysms
should be kept under surveillance with periodic ultrasonographic
measurements — every two to
three years for those smaller than 4.0 cm, and every
six months for larger aneurysms. Elective repair
should be considered for abdominal aortic aneurysms
measuring 5.5 cm or larger. If the patient is
a candidate for either open or endovascular repair,
referral to a randomized trial is the best option.
From the Center for Epidemiological and Clinical Research, Veterans
Affairs Medical Center, Minneapolis.
1.
Prinssen M, Verhoeven ELG, Buth J, et al. A randomized trial
comparing conventional and endovascular repair of abdominal aortic
aneurysms. N Engl J Med 2004;351:1607-18.
2.
Greenhalgh RM, Brown LC, Kwong GP, Powell JT, Thompson
SG. Comparison of endovascular aneurysm repair with open repair
in patients with abdominal aortic aneurysm (EVAR trial 1), 30-day
operative mortality results: randomised controlled trial. Lancet
2004;364:843-8.
3.
Hallett JW Jr, Marshall DM, Petterson TM, et al. Graft-related
complications after abdominal aortic aneurysm repair: reassurance
from a 36-year population-based experience. J Vasc Surg 1997;25:
277-86.
4.
Johnston KW, Canadian Society for Vascular Surgery Aneurysm
Study Group. Nonruptured abdominal aortic aneurysm: six-year
follow-up results from the multicenter prospective Canadian aneurysm
study. J Vasc Surg 1994;20:163-70.
5.
Lederle FA, Wilson SE, Johnson GR, et al. Immediate repair
compared with surveillance of small abdominal aortic aneurysms.
N Engl J Med 2002;346:1437-44.
6.
Collin J, Murie JA. Endovascular treatment of abdominal aortic
aneurysms: a failed experiment. Br J Surg 2001;88:1281-2.
7.
Cronenwett JL, Seeger JM. Withdrawal of article by the FDA after
objection from Medtronic. J Vasc Surg 2004;40:209-10.
8.
Anderson PL, Arons RR, Moskowitz AJ, et al. A statewide experience
with endovascular abdominal aortic aneurysm repair: rapid
diffusion with excellent early results. J Vasc Surg 2004;39:10-9.
9.
Lee WA, Carter JW, Upchurch G, Seeger JM, Huber TS. Perioperative
outcomes after open and endovascular repair of intact abdominal
aortic aneurysms in the United States during 2001. J Vasc Surg
2004;39:491-6.
10.
Laheij RJ, Buth J, Harris PL, Moll FL, Stelter WJ, Verhoeven EL.
Need for secondary interventions after endovascular repair of abdominal
aortic aneurysms: intermediate-term follow-up results of a
European collaborative registry (EUROSTAR). Br J Surg 2000;87:
1666-73.
11.
Vallabhaneni SR, Harris PL. Lessons learnt from the EUROSTAR
registry on endovascular repair of abdominal aortic aneurysm repair.
Eur J Radiol 2001;39:34-41.
12.
Beard JD, Thomas SM. Mid-term results of the RETA registry.
Br J Surg 2002;89:520. abstract.
13.
Carpenter JP, Baum RA, Barker CF, et al. Durability of benefits of
endovascular versus conventional abdominal aortic aneurysm repair.
J Vasc Surg 2002;35:222-8.
14.
Peppelenbosch N, Buth J, Harris PL, van Marrewijk C, Fransen
G. Diameter of abdominal aortic aneurysm and outcome of endovascular
aneurysm repair: does size matter? A report from EUROSTAR.
J Vasc Surg 2004;39:288-97.
15.
Ouriel K, Srivastava SD, Sarac TP, et al. Disparate outcome after
endovascular treatment of small versus large abdominal aortic
aneurysm. J Vasc Surg 2003;37:1206-12.
16.
The United Kingdom Small Aneurysm Trial Participants. Longterm
outcomes of immediate repair compared with surveillance of
small abdominal aortic aneurysms. N Engl J Med 2002;346:1445-52.
Copyright © 2004 Massachusetts Medical Society.

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