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Trans-Atlantic Debate
Part Two: Against the Motion. An Endovascular First Strategy is not the
Optimal Approach for Treating Acute Mesenteric Ischemia
N.T. Orr, E.D. Endean
*
Department of Surgery, University of Kentucky, Lexington, KY 40536, USA
There are a number of pathologic conditions that can result
in acute mesenteric ischemia (AMI). These include embolus
to a mesenteric vessel (usually the superior mesenteric
artery [SMA]); thrombosis of underlying atherosclerotic
disease; nonocclusive mesenteric ischemia; interruption of
the inferior mesenteric artery blood supply, as seen after
abdominal aortic aneurysm repair; mesenteric venous
thrombosis; and mechanical causes such as volvulus,
intussusception, torsion around adhesions, or internal hernia. For the purposes of this discussion, the focus will be on
mesenteric ischemia as caused by either embolic disease or
thrombosis of underlying atherosclerosis.
Since Klass first reported a successful operation to restore
the midgut blood supply, AMI has remained an uncommon
disease that is primarily addressed surgically.1 The presentation of AMI often presents a diagnostic challenge for a
number of reasons. Symptoms are often nonspecific and,
outside of imaging studies, there are no tests that reliably
make or exclude the diagnosis of AMI. This can lead to a
delay in diagnosis, which, in turn, can have catastrophic
consequences. Delay in diagnosis is the biggest factor that
contributes to a continued mortality rate as high as 30e
70% despite >50 years of operative intervention, as documented in contemporary reports.2e4 Despite the low incidence of this disease, as the mean age of the population
increases, the incidence of AMI will predictably rise.
With continued evolution of endovascular therapies, the
vascular surgeon is faced with the question of which is the
best technique to address AMI. Multiple recent studies have
attempted to clarify the optimal approach to treat AMI;
however, no definitive consensus has been reached.5e7
Therefore, the objective of this debate is to evaluate the
available literature and present an argument that an open
operative approach, as opposed to endovascular therapy,
should be the first-line and optimal treatment of AMI. The
thrust of the argument is that an open approach is best
because (1) it provides the ability to assess bowel viability
directly; (2) it decreases delay in restoring mesenteric blood
flow; (3) it eliminates the variables in physician expertise;
and (4) there is no proven mortality advantage with an
endovascular approach. Each of these four points will be
discussed in turn.
The goal of surgical intervention for AMI is threefold: reestablish blood supply to the ischemic bowel, resect all
nonviable bowel, and preserve as much bowel length as
possible. Bowel viability is the most important factor that
affects outcome in patients with AMI. Nonviable bowel, if
unrecognized, results in multisystem organ failure and
death. Massive bowel infarction is a nonsurvivable
condition. In the authors’ practice, when massive mid-gut
necrosis is found, the patient is closed and comfort care
measures are instituted, with no attempt to revascularize.
While this situation is extreme, the only way to determine
definitively the extent of bowel infarction is to visualize the
bowel. In other less extreme cases, failure to recognize even
localized segments of bowel infarction can be catastrophic.
The key to the long-term welfare of patients is the preservation of as much viable bowel as possible in order to
avoid short gut syndrome. Therefore, the early diagnosis of
mesenteric ischemia is essential for the preservation of
bowel and avoidance of the associated high morbidity and
mortality.8 Recent studies have shown that bowel resection
is required in 31e93% of AMI cases.6,9e12 These rates of
bowel resection mandate that a reliable assessment of
bowel viability be required regardless of the technique
employed to reestablish blood flow.
The proponents for an endovascular approach for AMI
argue that assessment of the bowel can be determined by
the patient’s clinical status and physical examination. It can
be argued that such an approach is risky for the patient.
Most patients with AMI are elderly, with multiple comorbid
conditions. These patients are often receiving pain medication and have unreliable physical examinations. While
imaging studies can identify occlusion of a mesenteric
vessel with a high degree of accuracy, there are no radiologic or laboratory studies that are sufficiently accurate to
identify the presence, or absence, of infarcted bowel. As a
result, the first sign of bowel infarction may be that the
clinical status of the patient worsens. Given the medical
condition of these elderly patients, their clinical status can
quickly degenerate and, with limited metabolic reserve,
their chance of survival in such circumstances is poor.
In a retrospective study, Arthurs et al. described that the
cohort of patients treated with an endovascular intervention was monitored in an intensive care unit.5 Abdominal
exploration was reserved for those who developed peritoneal findings on abdominal examination or had clinical
deterioration. They reported that a third (31%) of patients
treated with endovascular therapy avoided laparotomy.5
Conversely, almost 70% of patients required laparotomy,
and although the findings at the time of operation were not
documented, Arthurs et al. state that “necrotic bowel
requiring resection.negatively affected overall mortality”.5
Certainly, the avoidance of the complications associated
with abdominal exploration is commendable, but it can be
suggested that the risks associated with a delay in resecting
infracted bowel far outweigh the risk of a laparotomy. In
order for this method of clinical assessment to be effective,
European Journal of Vascular and Endovascular Surgery
Volume 50 Issue 3 p. 273e280 September/2015
serial monitoring of the patient by a provider skilled in the
diagnosis of peritonitis with the clinical acumen to suspect
bowel ischemia is mandatory. While this might be reproducible in a large academic center, smaller community
centers may not have the personnel to achieve such close
scrutiny with concern that the diagnosis of peritonitis would
be delayed. Also, many of these patients are very sick and
require intubation, which complicates the reliability of the
physical examination as the major determinant of bowel
ischemia.
Others may argue that superior imaging technology can
now adequately identify patients with bowel ischemia and
thereby predict who should undergo laparotomy. It is true
that multidetector computed tomography (CT) angiography,
as well as magnetic resonance angiography, have developed
rapidly over the last two decades. Additionally, the widespread availability of such technology often ensures that
most patients will undergo radiologic evaluation prior to
any surgical intervention. The presence of SMA occlusion
due to thrombosis or embolus can be accurately identified
on most CT angiography studies.13,14 However, multiple
examples have shown CT imaging to have low rates of ruling
out associated bowel ischemia.15,16 Indeed, Bani Hani et al.
found that in patients with bowel ischemia or necrosis only
34% had pneumatosis and portal venous gas.16 Therefore,
even the most sophisticated imaging techniques will have
difficulty reliably identifying patients with bowel ischemia.
It is also noteworthy that profound radiographic changes
are not predictive of infracted bowel versus ischemic bowel
(Fig. 1).
It is well established that the need to reduce treatment
delays for AMI remains the greatest challenge, as well as
the greatest opportunity, for reducing the morbidity and
mortality associated with this disease.12 The diagnosis of
AMI continues to be elusive in the early stages of the disease process. The most common presenting symptom is
acute-onset of vague abdominal pain.8,12 AMI can easily be
mistaken for more common intra-abdominal pathologies,
including pancreatitis, cholecystitis, diverticulitis, or bowel
obstruction. Therefore, it is common that significant time
delays have occurred by the time the diagnosis of AMI has
been made. It becomes imperative that restoration of blood
flow be accomplished quickly.
There is a direct relationship between prolonged times to
treatment and bowel viability. Small studies have shown
that patients with symptoms lasting < 12 h can undergo
revascularization without requiring bowel resection.17,18 In
one large, retrospective study of open versus endovascular
intervention by Arthurs et al.,5 the authors argued that a
delay in definitive treatment did not affect outcomes. As
proof, Arthurs et al. found that patients receiving endovascular treatment in their study presented with a median
of 62 h of symptoms, while patients in the open repair
group presented with a much shorter duration of symptoms
(26 h).5 It seems likely that the reason for these findings is
that patients with AMI who present with > 60 h of pain are
essentially “self-selecting” to a lower risk stratification and
it can be assumed that these patients either had a partially
277
Figure 1. Computed tomography scan of a patient who had acute
mesenteric artery occlusion and significant portal venous gas (arrows). After restoration of flow, no bowel resection was required
and the patient had a rapid recovery.
occlusive process or had well-developed mesenteric collateral vessels that maintained bowel viability. Indeed, in the
study by Arthurs et al.,5 an embolic cause of AMI was
present in 64% of patients treated with open operation
compared with 28% treated with an endovascular
approach. It is likely that the severity of pain and other
associated factors in patients with a mesenteric embolus
mandated an open approach, while patients with thrombosis of underlying occlusive disease had already developed
collateral flow. As is inherent in any retrospective analysis,
these types of selection biases cloud the true meaning of
the results. The same study also found that about half (48%)
of the endovascular cohort was initially treated with
chemical thrombolysis. The duration of thrombolysis lasted
from 1 day (58%) up to 3 days (5%). Although the chemical
thrombolysis may have allowed at least partial restoration
of blood flow early in its course, the fact that these patients
tolerated multiple days of thrombolysis again points to the
high degree of selection bias that is prevalent in all the
published reports comparing endovascular with open
treatment.
The patient response to intra-arterial treatment is highly
variable. Simó et al. demonstrated that two patients with
symptoms lasting > 18 h had a favorable response to
chemical thrombolysis, while the same therapy failed in
another two patients who had symptoms for only 6 h prior
to treatment.19 In evaluating the feasibility of percutaneous
stent placement in AMI, Wyers et al. found that the mean
operative time was 329 46 minutes.20 This is substantially
different than the procedure duration reported by Arthurs
et al. of 120 minutes and highlights the enormous variability
that exists between reported outcomes.5 The time necessary to access and stent potentially occluded vessels, or the
time required to deliver tissue plasminogen activator for
278
adequate treatment creates a substantial potential for delay
in definitive revascularization. Additionally, there is the
potential that the patient will not respond to thrombolysis
or that the occlusive disease cannot be crossed, further
contributing to delay in revascularization.
Successful revascularization using an endovascular
approach requires advanced catheter skills. While it is true
that recent graduates from vascular training programs
should have a wide range of catheter-based skills, these
skills are not uniform across the country. Additionally, good
imaging is required for cannulation of mesenteric arteries.
Many smaller hospitals rely on portable fluoroscopy units
with poorer imaging quality. Even in the best hands, there is
a certain percentage of patients in whom the endovascular
approach is unsuccessful. In one report the failure rate of
the initial endovascular treatment was approximately 9%,
with an overall technical success rate for endovascular
therapy of 87%.5 The failures are largely related to the
inability to cross an occluded lesion. These results were
published by an academic institution with highly skilled
interventionists who are exposed to large volumes of AMI
cases. It would be expected that in smaller facilities with
less exposure to complex endovascular cases, and specifically AMI, the failure rate would be higher. This inherently
adds to delay.
Another potential concern with limited experience by
physicians is that an attempt at endovascular treatment
could result in worsening of the condition. Endovascular
procedures have known complications, including dissection
of the vessel. Attempts to access an occluded vessel or
highly stenotic vessel could result in mesenteric dissection.
Should there be a need to covert to open revascularization,
such complications will potentially make on open repair
more difficult. Another potential complication with an
endovascular approach is distal embolization. The result of
the main trunk could be technically excellent, but a distal
embolus could result in unrecognized bowel infarction.
Likewise, use of a covered stent could occlude branch vessels, exacerbating the ischemia.
There are few studies that directly compare endovascular
with open surgical repair for AMI, and the author’s of this
debate are unaware of any randomized trials. All studies to
date have inherent selection bias that dictates which
approach is chosen for treatment of an individual patient.
Included in such bias are the patient’s presenting findings,
comorbid conditions, physical examination findings, and the
expertise of the treating physicians. It would seem that in
studies comparing the open and endovascular approach for
AMI, open repair is preferentially chosen for patients who,
based on presentation, have infracted bowel. In this patient
population, these are patients who are likely to be more
critically ill at the time of presentation. As such, it would be
expected that they should fare worse than the patient who
would seem to tolerate the additional time required to reestablish flow with endovascular approaches. Yet, the small
studies that are available show no difference in outcome
and specifically fail to demonstrate improved outcome with
patients treated with an endovascular approach.
Trans-Atlantic Debate
Endovascular treatment has made significant advances. It
is now possible to use such techniques for the treatment of
AMI. However, the question is not if it can be done, but
should it be done? While some selected patients will do
well with an endovascular mesenteric revascularization, in
general, it is concluded herein that there is no proven
benefit to an endovascular approach for patients with AMI
and, in fact, it is suggested that such an approach may
actually place patients at risk for increased morbidity and
mortality. Until there is an accurate way to assess for the
presence of bowel infarction, it would seem that the safest
approach in the care for these critically ill patients is
definitive open revascularization with an assessment of
bowel viability. Liberal use of second-look laparotomy for
questionable bowel should be encouraged in order to
preserve bowel length and avoid the complications of short
gut and to identify infracted bowel before perforation and
contamination occurs.
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2 Bradbury AW, Brittenden J, McBride K, Ruckley CV. Mesenteric
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4 Kassahun WT, Schulz T, Richter O, Hauss J. Unchanged high
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5 Arthurs ZM, Titus J, Bannazadeh M, Eagleton MJ, Srivastava S,
Sarac TP, et al. A comparison of endovascular revascularization
with traditional therapy for the treatment of acute mesenteric
ischemia. J Vasc Surg 2011;53:698e705.
6 Beaulieu RJ, Arnaoutakis KD, Abularrage CJ, Efron DT,
Schneider E, Black 3rd JH. Comparison of open and endovascular treatment of acute mesenteric ischemia. J Vasc Surg
2014;59:159e64.
7 Resch TA, Acosta S, Sonesson B. Endovascular techniques in
acute arterial mesenteric ischemia. Semin Vasc Surg 2010;23:
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Panneton JM, et al. Contemporary management of acute
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9 Yun WS, KKm Lee, Cho J, Kim HK, Huh S. Treatment outcome in
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10 Alhan E, Usta A, Cekic A, Saglam K, Türkyilmaz S, Cinel A.
A study on 107 patients with acute mesenteric ischemia over
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et al. Revascularization for acute mesenteric ischemia. J Vasc
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12 Kougias P, Lau D, El Sayed HF, Zhou W, Huynh TT, Lin PH.
Determinants of mortality and treatment outcome following
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14 Aschoff AJ, Stuber G, Becker BW, Hoffmann MH, Schmitz BL,
Schelzig H, et al. Evaluation of acute mesenteric ischemia: accuracy of biphasic mesenteric multi-detector CT angiography.
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*
Corresponding author.
Email-address: [email protected] (E.D. Endean)
1078-5884/$ e see front matter Ó 2015 Published by Elsevier Ltd on behalf of European Society for Vascular Surgery.
http://dx.doi.org/10.1016/j.ejvs.2015.04.026
EDITORS’ COMMENT
Trans-Atlantic Debate: Is an “Endovascular First” Strategy the Optimal
Approach for Treating Acute Mesenteric Ischemia?
A.R. Naylor, Editor-in-Chief, European Journal of Vascular and Endovascular Surgery
*
Vascular Research Group, Division of Cardiovascular Sciences, Clinical Sciences Building, Leicester Royal Infirmary, Leicester LE2 7LX, UK
T.L. Forbes, Associate Editor, Journal of Vascular Surgery
Division of Vascular Surgery, University of Toronto, Toronto, ON, Canada
Notwithstanding the headline debate about whether an
“endovascular first” or an “open surgery first” strategy is
preferable or safer, the most important issue raised by our
debaters (and one which should concern all of us) is that a
diagnosis of acute mesenteric ischemia (AMI) is still
invariably delayed and usually only considered once the
patient has become too ill to undergo any form of meaningful intervention. The data from the US National Inpatient
Sample, which showed that only 15% of patients with AMI
were actually treated and that only 3% had the chance to
benefit from endovascular or open revascularization, makes
extremely depressing reading. Put another way: almost nine
out of every 10 patients with a diagnosis of suspected AMI
will undergo no active treatment. Such bleak statistics demand that medical professionals (of all disciplines) be made
more aware of the importance of at least considering a
diagnosis of AMI in patients.
Returning to the “meat” of the debate, the contributors
have provided positive and negative data regarding their
respective positions. That is not surprising, given the nature
of a debate. We suspect, however, that a significant proportion of our surgical readers will rarely (or never) consider
an “endovascular first” strategy for the treatment of patients
with AMI (unlike patients with chronic mesenteric ischemia),
largely because of an intuitively held belief (espoused by Drs.
Orr and Endean) that endovascular strategies have little to
offer in these acute, life-threatening situations, and that
emergency laparotomy is mandatory in order to gauge the
severity of ischemia, enable revascularization, and allow the
resection of compromised bowel before it worsens and
precipitates multiorgan failure. However, Martin Björck has
also shown that surgeons may have been wrong to uncritically dismiss a role for an “endovascular first” strategy. This is
supported by international registries reporting that up to
50% of contemporary arterial revascularizations for AMI now
follow an “endovascular first” strategy, with bailout surgical
bypass being possible in up to half of those cases where an
endovascular intervention failed to recanalize the superior
mesenteric artery. One would not expect to have observed
such an increase in the proportion of interventional therapies if an “endovascular first” strategy was associated with
poorer outcomes compared with the traditional open surgical approach.
There are obvious advantages to either strategy. Endovascular therapy is less invasive, can be done under local
anesthesia, avoids a major laparotomy in compromised individuals, and (perhaps most importantly) finishes with
completion angiography in order to identify and treat residual thrombus/defects, thereby optimizing the overall
quality of the revascularization. The “Achilles’ heel” of an
“endovascular first” strategy, however, is determining exactly
when someone needs a second-look laparotomy to identify
the patient with persisting focal bowel ischemia before it
perforates. Martin Björck advocates a liberal approach to
second-look laparotomy, but it is not always apparent when
one is required. The “open surgery first” approach, as stated