Key Words
Pseudoaneurysm - Omental wrapping - Graft infection - Aneurysm - Aorta - Carotid artery
Introduction
Prosthetic infection following aortic surgery is a rare but grave complication, which
yields an early mortality as high as 25%–42%[1]. In coexistence with prosthetic pseudoaneurysm, chest entry for reoperation is complicated
due to the potential danger of aortic injury[2]. Current treatment of choice for infected prosthetic pseudoaneurysm includes aggressive
graft resection with extensive debridement and negative-pressure wound therapy[1]
[3]. Utilization of omental wrapping has also been described and can be performed with
and without concomitant graft replacement[4]
[5]. Surgery for omental prosthesis coverage, however, usually requires the patient
to be in stable condition. We herein describe the case of a 57-year-old female patient
who underwent successful treatment by means of a two-stage approach with aortic prosthesis
replacement, extensive debridement and antiseptic lavage in a first step, followed
by an omental flap wrapping of the new graft in a second step 24 hours later. The
operative approach and general considerations for arterial cannulation prior to re-sternotomy
are discussed.
Case Presentation
A 57-year-old female patient was referred to our clinic from a tertiary care center
in poor general condition due to a sudden sternal bleeding.
Four months prior to this incident, the patient underwent emergent surgery due to
an iatrogenic Type A dissection after an unsuccessful angioplasty revascularization
attempt of a chronically occluded right coronary artery. At the time, supracoronary
aortic replacement and a single venous bypass originating from the ascending prosthesis
were performed. During this first operation the right subclavian artery was used for
arterial cannulation. Postoperatively two re-explorations were mandated: due to significant
pericardial effusion on postoperative day 11 and mediastinitis on postoperative day
14. Pathology identified methicillin-resistant Staphylococcus aureus (MRSA) as the causative pathogen. After antiseptic situs irrigation and parenteral
antibiotic treatment with vancomycin the patient could be discharged with normal wound
condition, no signs of infection and negative pathology for MRSA.
Upon admission the patient was in hypovolemic shock and unconscious. Computed tomography
prior to transportation indicated an infected pseudoaneurysm of the ascending aortic
graft at the distal anastomosis forming a sternal fistula ([Figure 1]). After adequate fluid and vasopressor administration on the cardiac intensive care
unit the patient regained consciousness just before emergent reoperation. Intubation
was not required preoperatively. Relevant heart valve involvement was ruled out by
means of transesophageal echocardiography.
Figure 1. Preoperative computed tomography. (Red asterisk) Ascending aortic prosthesis. (Red
arrow) Infected aortic prosthesis pseudoaneurysm with adjacent hematoma.
As safety precaution prior to median re-sternotomy—due to the impending danger of
pseudoaneurysm rupture and adjacent adhesions of the right subclavian artery—in addition
to the femoral artery the right carotid artery was surgically exposed for direct cannulation.
Cardiopulmonary bypass (CPB) was then established via arterial perfusion through the
right carotid and the femoral artery. Venous cannulation was via the right femoral
vein. After cooling to an esophageal temperature of 18°C, femoral perfusion was discontinued.
During low flow antegrade perfusion via the carotid artery, median re-sternotomy was
performed. The sternal bone structure showed good blood supply and no signs of infection.
The old hematoma was carefully removed and the pseudoaneurysm at the distal anastomosis
of the aortic prosthesis identified. Upon inspection partial detachment of the prosthesis
due to suture dehiscence was evident. Owing to mediastinal adhesions, the brachiocephalic
vein sustained injury and was repaired using a small pericardial patch. Cold cardioplegia
(Bretschneider HTK solution; Köhler Chemie, Alsbach-Hähnlein, Germany) was administered
into the left coronary ostium and into the venous bypass graft to the right coronary
artery. The right coronary ostium was obliterated.
The infected prosthesis was removed and sent for pathology, isolating MRSA again as
the underlying pathogen. After completion of the distal anastomosis and before finishing
the proximal anastomosis, the prosthesis was clamped (22 mm Dacron, Hemashield Platinum,
Flagstaff, Arizona, USA) and the rewarming process initiated. Circulatory arrest time
under hypothermia was 20 minutes. The venous bypass graft was reinserted into the
ascending prosthesis. Total CPB time was 194 minutes including 75 minutes of ischemia.
After extensive wound debridement and antiseptic surgery site irrigation (Povidon-Iod,
Betaisodona, Mundipharma GmbH, Limburg, Germany), drainage tubes for continuous lavage
were inserted and the sternum was closed.
Twenty-four hours later, the second look followed. At that time the mediastinal swab
taken during the first operation did not show bacterial growth. The sternum was reopened
and old hematoma removed. Again, wound debridement was performed. Through an epigastric
median laparotomy, the greater omentum was exposed along the transverse colon and
gastric portion. The omentum was then translocated as a pedicle retrosternally into
the mediastinum and wrapped around the ascending aortic prosthesis ([Figure 2]). After placement of drainages the sternum was closed.
Figure 2. Intraoperative picture during omental wrapping procedure. (White asterisk) The mobilized
omentum. (White arrow) Exposed new ascending aortic graft.
The postoperative course was uneventful without neurologic sequelae. The antiseptic
lavage was continued for 72 hours postoperatively and changed to clear irrigation
solution for additional 48 hours. The drainage tubes were then removed four days later
after consecutive negative pathology results. The patient was discharged on postoperative
day twelve. Computed tomography 3 days and 3 years postoperatively revealed a patent
aortic prosthesis with no signs of recurring infection or aneurysm ([Figure 3]). At the last routine follow-up 10 years after the first surgery the patient was
in good health, suffering only from mild dyspnea due to unrelated comorbidities.
Figure 3. Computed tomography 3 years postoperatively. (Red arrow) The omental wrap. (Red asterisk)
The new aortic prosthesis covered by the omentum.
Discussion
Formation of pseudoaneurysm after aortic surgery is a known complication warranting
a carefully planned approach for reentering the chest during reoperation in order
to circumvent free perforation[2]
[6]. Graft infection and mediastinitis—also rare complications following aortic surgery—represent
additional challenges for the re-operating surgeon in their own right[1]
[3]. In case these conditions coincide, a coherent surgical approach is mandatory for
successful surgery.
Reoperation for an aortic pseudoaneurysm becomes necessary after up to 0.5% of all
cardiovascular surgical cases, and the initial approach for re-entering the chest
is of major importance[2]. In our case the right carotid artery was used for direct arterial cannulation and
antegrade cerebral perfusion. The possibility of being incapable of safely exposing
the right subclavian artery due to pronounced adhesions and furthermore not being
able to clamp the innominate artery without endangering the pseudoaneurysm located
in the near vicinity—and subsequently failing selective cerebral perfusion—led to
this decision.
Successful re-sternotomy using comparable preemptive techniques for selective cerebral
perfusion in patients with large pseudoaneurysms have already been described[2]
[7]. Although in some cases—where direct carotid cannulation was used for selective
cerebral perfusion—adverse neurologic events were reported, our patient did not suffer
from any neurological deficit, neither temporary nor permanent.
Another important comment concerning hypothermic arrest prior to entering the chest
is hypothermia induced ventricular fibrillation. Although this complication did not
occur in our patient, it may potentially lead to left ventricular distension due to
volume overload, causing permanent cardiac damage. To prevent this, emergency vent
placement into the left apex—analogous to the transapical transcatheter approach for
valve implantation—represents a feasible option[8].
Current recommendations for a therapeutic algorithm of vascular graft infections include
wound debridement, vacuum assisted closure therapy and subsequent myoplastic reconstruction
if necessary[3]. In cases with abscess or pseudoaneurysm, early graft replacement should be performed[1], preferably using biological tissue grafts. It has been shown that graft coverage
by means of the greater omentum may function as a feasible alternative to graft removal
for patients with graft infection and mediastinitis in stable condition[1]
[4]
[5]. Owing to the patient's critical condition prior to and during the initial reoperation
and resection of the infected prosthesis, we chose to perform the omentum-plasty in
a second stage. A variation of our strategy may have been to leave the thorax open
after the first stage. Due to the good condition of the sternum we decided in favor
of a primary sternal closure giving more stability and effectively ensuring continuous
antiseptic lavage between stages.
The described two-stage procedure for an infected aortic graft pseudoaneurysm is a
feasible method for rescue surgery of critically ill patients. Primary carotid artery
cannulation for antegrade selective cerebral perfusion during hypothermic circulatory
arrest plus extensive prosthetic replacement with situs irrigation, followed by an
omentum flap, wrapping the new prosthesis in a second stage, may yield excellent long-term
results in highly selected patients.
