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Click here to read this article as a CME activity
Mount Sinai School of Medicine, New York, New York
Accepted for publication February 27, 2008.
* Address correspondence to Dr Etz, Department of Cardiothoracic Surgery, Mount Sinai School of Medicine, One Gustave L. Levy Pl, New York, NY 10029 (Email: christian.etz{at}mountsinai.org).
Presented at the Fifty-fourth Annual Meeting of the Southern Thoracic Surgical Association, Bonita Springs, FL, Nov 7–10, 2007.
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Abstract |
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 Top Abstract IntroductionPatients and MethodsResultsCommentDiscussionReferences |
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Methods: We reviewed 869 patients with ascending aorta/root repairs (1995 to 2005), principally for atherosclerotic and degenerative aneurysms and chronic and acute type A dissections. Arterial cannulation was through the ascending aorta (AAC) in 157 patients, the femoral artery (FAC) in 261, and the right axillary artery (AXC) in 451. Patients cannulated at different sites were compared for preoperative comorbidities and outcomes (mortality and stroke) for each cause.
Results: Of the 122 patients with atherosclerotic aneurysms, 66 with right AXC had significantly better outcomes (p = 0.02): 64 of 66 survived vs 24 of 26 with FAC and 27 with 30 of AAC; no strokes occurred (vs 2 of 26 with FAC and 4 of 30 with AAC). No significant advantage for AXC was found with ascending aortic operation in 495 degenerative aneurysms, 106 chronic, or 65 acute type A dissections, 41 patients with endocarditis, or in 18 with aneurysms of other causes; AXC was associated with a significantly better outcome (p = 0.05) in the 869 patients taken together.
Conclusions: AXC resulted in superior survival and neurologic outcome in patients with atherosclerotic aneurysms and a marginally better outcome than with cannulation at other sites during proximal aortic procedures for all causes. This study supports AXC in patients with atherosclerotic disease who require complex cardiothoracic operations and in patients requiring proximal aortic intervention regardless of cause.
Injury to the central nervous system remains one of the major causes of morbidity and mortality after proximal aortic and arch operations, affecting not only quality of life postoperatively but also resulting in prolonged hospitalization and increased cost of treatment. The cause of most major cerebral insults after ascending/aortic root reconstruction is stroke. Two influences on the incidence of stroke after replacement of the aortic arch and ascending aorta are the site of cannulation for cardiopulmonary bypass (CPB) and perfusion technique.
The preferred site of cannulation for CPB is usually the ascending aorta, but in patients with severe atherosclerotic aneurysm disease, central cannulation enhances the potential for embolization into the cerebral circulation, resulting in focal lesions producing neurologic injury. When the ascending aorta is unsuitable, cannulation of the femoral artery (FAC) is a commonly used alternative. But retrograde flow in a severely atherosclerotic and diseased aorta poses major risks, including dislodgement of plaques and aortic dissection, both of which may lead to cerebral as well as peripheral injury [1–3].
For these reasons, cannulation of the axillary artery (AXC) has become increasingly widespread and is more frequently being used for ascending aorta/root repair [4]. Axillary artery cannulation preserves antegrade flow in the descending aorta while eliminating some of the risks associated with direct cannulation of the ascending aorta (AAC). It lowers the potential for embolization into right-sided cerebral vessels by perfusing them with flow that has not traversed the arch. Axillary artery cannulation also eliminates the sandblasting effect of turbulent flow from a catheter tip close to atherosclerotic lesions in the ascending aorta or aortic arch, and thus also reduces the risk of embolization into left-sided cerebral vessels. Arterial inflow through the axillary artery also increases the ease of using selective cerebral perfusion during arch repairs, which allows the surgeon to construct open distal anastomoses while the lower body is kept hypothermic during circulatory arrest.
Not surprisingly, AXC has been advocated as particularly suitable for CPB in patients with severe atherosclerotic disease prohibiting femoral or direct aortic cannulation [1, 5]. Indirect AXC through a side graft has been demonstrated to reduce perfusion-related morbidity and stroke risk after complex cardioaortic operations that necessitate circulatory arrest [6]. We undertook this retrospective evaluation of the influence of direct AXC and its effect on survival and neurologic outcome after aortic root/ascending aortic repairs for ascending aortic disease of differing causes in 869 patients requiring proximal aortic repair.
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionReferences |
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An urgent or emergency proximal aortic repair was done in 80 patients. The overall mean age was 58 ± 18 years; 589 patients were men (67.7%), and 407 (46.8%) were aged 60 years or older. Of these, 184 patients (21%) had undergone previous cardioaortic procedures. Table 1 reports the clinical profiles of the patients in detail, as well as potential risk factors for death and stroke, allowing comparison of those who underwent AXC with those who had AAC or FAC for CPB.
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Indications
The principal indication for aortic root/ascending aorta reconstruction in 495 patients was a degenerative aortic aneurysm (Table 2). An atherosclerotic aortic aneurysm was present in 122 patients, chronic dissections in 106, and acute dissections in 65. Aortic valve endocarditis affected the root in 14 patients, and 40 patients had other pathologic conditions.
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Perfusion warming was performed at the end of the procedure with the gradient between the esophageal and blood temperature maintained at less than 10°C. Warming was maintained until the esophageal temperature reached 35°C and bladder temperature exceeded 32°C.
Technique for Axillary Artery Cannulation
Our technique for direct AXC has previously been described in detail [7]. Briefly, arterial pressure is routinely measured with a left radial artery cannula. Before the median sternotomy, a 6-cm transverse skin incision is made approximately 1 cm below the middle and lateral part of the right clavicle (deltopectoral groove). Following the direction of its fibers, the pectoralis major muscle is separated and the underlying pectoralis minor muscle retracted laterally. The axillary artery is identified by palpation and then gently mobilized by sharp dissection without touching the medial and lateral brachial plexus cords posterior to the artery. The artery is then controlled with loops of silicone elastomer tape.
After the administration of heparin, the axillary artery is occluded distally with a silicone elastomer vessel loop, and a transverse or longitudinal arteriotomy is done. The axillary artery is then cannulated directly using a 20F to 26F wire-reinforced right-angled flexible cannula (axillary access arterial cannula, Edwards Lifescience LLC, Irvine, CA). After proximal clamp removal, the cannula is advanced 3 cm into the artery, and the snare on the vessel tape is tightened. The cannula is held in place by a ligature on the snare and a skin stitch at the lateral end of the incision. Free backflow of blood is assured before perfusion is initiated. At the end of the procedure, the artery is repaired with a 6-0 polypropylene continuous suture.
Aortic Root Reconstruction
A button Bentall operation was done in 91% of patients in this study, with a modification of the original technique described by Kouchoukos and coworkers [8] in 1991. The Cabrol technique was used in 4%, and 5% of patients had a classic Bentall procedure. Almost all operations were performed with an open distal anastomosis, often with hemiarch replacement. Our current technique and its rationale for using either a mechanical or biologic conduit [9] have been described in detail elsewhere [10].
Statistical Methods
Data were entered in an Excel spreadsheet (Microsoft Corp, Redmond, WA) and transferred to SAS software (SAS Institute, Cary, NC) for data description and analysis. Characteristics and risk factors in this sample of patients are described as percentages or as means and standard deviations and compared among the cannulation sites by 
2 tests or analysis of variance, respectively. Patients cannulated at different sites were compared for the hospital outcomes of death and stroke for each of the aforementioned indications. The 2 tests for trend within etiologic groups were used to compare aortic, femoral, and axillary cannulation sites for death (with or without stroke), stroke survival, and uneventful recovery. Significant findings were checked by stratifying the data on groups of calendar years representing different periods of clinical practice—1990 to 1998, 1999 to 2002, and 2003 to 2007—and by comparing axillary and nonaxillary cannulation for the frequency of the adverse outcome of stroke or death.
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Results |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionReferences |
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Outcome
Overall hospital mortality—defined as death in the hospital or within 30 days postoperatively—was 4.6%. Adverse outcome was defined as postoperative death or stroke within 30 days after operation, with postoperative deaths occurring before discharge from the hospital included as adverse outcome even if the hospital stay extended beyond 30 days. An adverse outcome occurred in 6% of patients, and 2% had permanent strokes.
In 122 patients with atherosclerotic aneurysms, AXC in 66 was associated with a significantly better outcome (p = 0.02, Table 3). Of patients with AXC, 64 of 66 (97%) survived vs 24 of 26 (92%) with FAC and 27 of 30 (90%) with AAC. None of the patients with AXC had a stroke, in contrast to 2 of 26 (8%) with FAC and 4 of 30 (13%) with AAC. Overall, adverse outcome was seen in 2 of 66 patients who had AXC for atherosclerotic disease vs 9 of 56 with non-AXC (p = 0.01). Although some demographic variability in possible risk factors for death or stroke are apparent among patients who underwent cannulation at different sites (Table 1), no consistent differences suggesting decreased risk in the AXC group could be demonstrated.
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionReferences |
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Although no clear advantage of AXC for groups without atherosclerosis was shown when they were analyzed separately, AXC was seen to be of significant benefit in avoiding the adverse outcome of stroke or death in the group as a whole. This was true even though patients undergoing AXC where older and more likely to have coronary artery disease or chronic obstructive pulmonary disease, or both. A 50% decrease in adverse outcome was seen in the patients with AXC for acute dissection, and a larger patient sample might well have shown a statistically significant advantage in this group. The axillary artery is now our cannulation site of choice in patients with both atherosclerotic aneurysms and dissections, and even a conservative interpretation of the results suggests that use of AXC was not associated with any increase in adverse outcome in patients with degenerative aneurysms, acute or chronic dissections, or proximal aortic operations for miscellaneous other aortic pathologies.
The utility of AXC in facilitating access to CPB in patients with previous cardioaortic intervention has previously been recognized. We have shown, in another study, that AXC is an independent factor favoring long-term survival after aortic root/ascending aorta reoperations, and there is some indication that AXC may provide some advantage for 30-day survival in aortic reoperations as a whole.
Axillary artery cannulation also provides an excellent route for selective cerebral perfusion during aortic arch procedures, providing optimal protection during circulatory arrest and thus reducing neurologic injury and early mortality [7, 11, 12]. In proximal aortic operations, however, the circulatory arrest time is usually shorter, and therefore, optimal cerebral protection is arguably less critical. This may perhaps contribute to the difficulty in demonstrating any superiority of this approach in the current study in patients whose underlying disease did not predispose them to embolization.
The question of whether one should initiate direct AXC or use a graft is somewhat controversial. We have not encountered problems with direct cannulation and therefore see the use of a graft as an unnecessary additional step. But we cannot reiterate frequently enough the importance of keeping the interval of AXC as brief as possible to avoid complications secondary to distal ischemia. It should be noted that use of a graft does not eliminate complications: both dissection and hyperperfusion of the arm have been described [13].
Because the choice of cannulation site varied with surgeon preference and with date of operation, this study is subject to the usual limitations of retrospective reviews. Therefore, notwithstanding our observation that patient characteristics did not appear to differ over time or between patients in the various cannulation groups, our analysis must be regarded as suggestive rather than conclusive.
The results of the current review suggest that more widespread adoption of AXC for complex aortic operations, particularly in atherosclerotic aneurysms—and possibly also its use in patients with atheromatous lesions undergoing coronary or valve operations—should be encouraged.
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Discussion |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionReferences |
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DR ETZ: No. Aneurysms were classified according to a pathological definition.
DR MARTIN: So you had pathology specimens on all these?
DR ETZ: On all cases.
DR MARTIN: Did you look at atheromatous disease? Was that included in that?
DR ETZ: Atheromatous disease was included, but not all of the 122 patients had what we label "clot or atheroma." Visible atheromata are not required for a classification for atherosclerotic disease. The aneurysm was classified as atherosclerotic if there were signs of systemic atherosclerosis and if the appearance of the aneurysm in the operating room and the specimen pathology were consistent with this diagnosis. In the severe cases, visible and sometimes mobile atheromata were present.
DR MARTIN: If I might address the panelists, I don't know how you define it, but I am a little confused at the difference between those two groups and what we see generally.
DR HAZIM J. SAFI (Houston, TX): Well, I am confused too. You said that you chose axillary cannulation because you knew that atherosclerosis was present. We know that aneurysm is always a medial disease and that atheromatous plaque is an intimal disease, and that sometimes they are superimposed. We use transesophageal echo to discern these conditions. If there is atheromatous plaque of grade 1 or 2, we will go ahead and cannulate whatever is convenient. However if it is atheromatous, with an appearance like cauliflower, then this will affect our choice of cannulation. Was that the way you approached it?
DR ETZ: It is evident that I should clarify my statements. The site of cannulation was not chosen because we were able to identify those patients at unusually high risk of embolism beforehand. We began using the axillary cannulation technique thinking that it would be universally useful. Our classification of aneurysms is a somewhat retrospective definition using the clinical picture at the time of surgery, and the pathology. We used axillary cannulation increasingly starting in 1999–2000, regardless of what was known preoperatively about the etiology of the aneurysm.
DR NICHOLAS T. KOUCHOUKOS (St. Louis, MO): Can you explain the difference between the atherosclerotic group and the other groups in terms of the morbid events?
DR ETZ: We came up with two or three possible explanations. Obviously the flow direction is different if you cannulate using the axillary artery: you have retrograde flow in the innominate artery, which possibly protects the cerebral circulation from clots that you may dislodge when you manipulate the aortic root. This difference may be more significant when you compare axillary to femoral cannulation, which results in retrograde flow in the arch, and can flush distal atheromic debris into the cerebral circulation.
Secondly, direct aortic cannulation is known for a sandblast effect that increases local pressures and creates turbulent flow, potentially directly dislodging plaques in the arch. We think one of the most important reasons for the success of axillary cannulation is that it provides a gentler form of antegrade flow.
DR JOHN S. IKONOMIDIS (Charleston, SC): I have a question for the speaker and a question for the panel. The question for the speaker is, these patients included patients that had ascending replacements and in those that extended into the hemiarch. So did you separate your analysis on neurologic outcome by those that just had an ascending replacement where you presumably put the cross-clamp on the ascending aorta vs those that had hemiarch replacements where the clamp was probably more likely on the innominate artery?
DR ETZ: We did not distinguish ascending aorta from hemiarch replacements. They were all done with an open distal anastomosis, so we thought this distinction was not really important.
DR IKONOMIDIS: And the question I have for the panel is, advantages and disadvantage of direct cannulation of the axillary artery versus placement of a side graft.
DR MARTIN: Before we answer that, John, could I make one comment before we get on that specific thing? First, I would like to compliment you on your presentation and on the choice of a very timely topic. We recently looked at our arch experience. In the last 6 years we have performed 660 arch aneurysm operations requiring circulatory arrest with a similar experience in terms of mortality and a similar experience in terms of stroke rate. From your paper, I would hesitate to recommend to the audience that every aneurysm that is "atherosclerotic" that you should use an axillary cannula. I am personally not an axillary cannulation fan and have actually told my residents the axillary artery in many cases is not your friend. So I would just like to make a comment, and I would be very, very interested in the rest of the esteemed panel's thoughts on this, that I would not at the moment say that axillary cannulation is the cannulation of choice for ascending and arch aneurysms.
DR JOSEPH S. COSELLI (Houston, TX): We are completely on the other side of that issue. We over the last few years have defaulted to the axillary artery as the site of perfusion in these cases and have probably in less than 1% of cases actually cannulated the femoral artery. Our cannulation is a little different. We don't cannulate with a plastic cannula but sew on a Dacron [DuPont, Wilmington, DE] side graft. That probably eases into some of the other aspects of that question in that it allows us with a right radial artery line to monitor the perfusion pressure as well as the flows. When I am unable to do that with a Dacron graft, you can just simply put a little catheter, stick it in the side of the graft and monitor the pressure in the graft when the right radial art line is not available to you for whatever reason. I would like to know from your group what circumstances in your current practice would you use the femoral artery, and could you expand upon your concepts of the proper flows and monitoring of pressures and cerebral perfusion?
DR ETZ: The pressure is only monitored in the left radial artery. Femoral artery cannulation is almost never used anymore; its use has been gradually decreasing over the last 10 years. Axillary artery cannulation is almost always utilized. In 2% to 3% of patients, however, the artery is small or friable, or we do not observe torrential backflow through the cannula. If there is not unequivocal free flow, we go to an alternate site. We have published a report of complications of direct axillary cannulation in the Annals of Thoracic Surgery.
DR MARC R. MOON (St. Louis, MO): Can we get Dr Kouchoukos's thoughts on axillary cannulation versus femoral?
DR KOUCHOUKOS (St. Louis, MO): We do what Dr Coselli has described, and that is, use a side arm exclusively. We have never actually directly cannulated. And I would like to ask you if you have any complications related to direct cannulation of the axillary artery?
DR ETZ: Interestingly, in this series, there were no complications with malperfusion of the arm, but it may be worthwhile noting that we try to keep the time of the cannulation really short. The cannula is put in right before CPB, and it is taken out as soon as possible. One localized dissection of the arch required repair 4 years later. In four or five cases, owing to friability, the artery was ligated rather than repaired without ischemic sequelae.
DR KOUCHOUKOS: Do you have some bias anastomosing a graft to the artery?
DR ETZ: I discussed this with Dr Griepp before I came here to get his opinion on this question. He thinks that indirect cannulation is an option, but he has not done it because he has encountered few problems using direct cannulation and worries that there may be a problem, with a side graft, of hyperperfusion of the arm; he also doubts that use of a graft is any less likely to cause arterial injury or dissection. But he does not necessarily feel that a graft is an inferior option.
DR SAFI: We rarely use the axillary artery, but when we do, often in some cases at the insistence of my associate, Dr Tony Estrera, we use a Dacron graft because of the relative ease of use. Otherwise we use the femoral artery and the ascending aorta, and we have very good results with stroke. The important issue is not the mode of cannulation, but the question of how well you can perfuse the brain. We feel the use of transcranial Doppler is essential to assess degree of perfusion. Perfusion can be estimated using radial artery and pressure measures. We find that when we have a good echo, the transcranial Doppler, we are able to determine flow to the brain. This requires continuous monitoring. I think there is a need to train a lot of people to use this monitoring technique to reduce the guesswork that sometimes occurs.
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