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Discussion: Session 2—Aortic Arch Aneurysm and Endoluminal Stents
Discussion: Session 2—Aortic Arch Aneurysm and Endoluminal Stents Moderator: Nicholas T. Kouchoukos, MD Panelists: Teruhisa Kazui, MD, Hazim J. Safi, MD, David Spielvogel, MD, Hideo Adachi, MD, Enio Buffolo, MD, PhD, R. Scott Mitchell, MD, Hiroaki Hosokawa, MD, Michael L. Marin, MD, FACS, and Akihiko Usui, MD MR STEPHEN WESTABY (Oxford, England): With regard to the presentation from Mt. Sinai, I know their preference used to be to put the three head vessels (the brachiocephalic vessels) together on one graft and reimplant them on a Carrel button, and now they have gone on to sectioning the separate vessels. Is this making a difference? Is it not just making it more complicated? DR DAVID SPIELVOGEL (New York, NY): The reason we moved to this technique is that we found that, when using the Carrel patch technique in elderly patients, the origins of the brachiocephalic vessels were often very diseased. And we found that we were spending a lot of time trying to remove the atherosclerotic plaques and loose debris, and that perhaps this was contributing to some of our strokes. But we also noticed that if you went just a centimeter or two above, to the brachiocephalic vessels themselves, that they were often free and soft, with no disease. Intuitively you would say, why don’t we just move our resection just a little further north and use a trifurcated graft or a bifurcated graft depending upon the situation. I have to admit that part of our motivation came from a video that was presented at the last symposium by Dr Taniguchi. He developed a technique where he constructed his elephant trunk in the distal ascending or mid arch, away from the nerves, with the idea that this would reduce the morbidity associated with respiratory failure and prolonged intubation. And then we thought, why not move our resection also to the brachiocephalic vessels and move some of our elephant trunks to the mid arch, and avoid the nerves and the morbidity associated with recurring laryngeal nerve palsy? So I think that in the population where you have a lot of atherosclerotic disease (and I am sure everyone knows that the population coming to surgery is increasing in age every year), that this has motivated us to move away from using just the arch, just the Carrel patch. MR WESTABY: Would you use the trifurcated graft in an acute dissection? DR SPIELVOGEL: I did 1 patient with an acute dissection: a woman who was 85 years of age, with a calcified aorta with a type A dissection. Unfortunately, she did not survive. The technique, of course, worked well, but she died for other reasons. But I think you can use the technique successfully in a dissection. If the tear is in the Presented at the Aortic Surgery Symposium VIII, May 2–3, 2002, New York, NY.
© 2002 by The Society of Thoracic Surgeons Published by Elsevier Science Inc
ascending aorta, you should replace just the ascending aorta, but if the tear is in the arch, this technique certainly is an option. DR TIRONE DAVID (Toronto, Ontario, Canada): A question for Dr Kouchoukos and Dr Safi. Why not do a sternotomy in a single stage? In other words, do your arch operation, lift the heart, open the posterior pericardium, and that is where the descending thoracic aorta is. You do not have any retraction of the lungs, you do not have to do anything. Staple the aorta proximally and distally. I have not done as large a number as you, but in the eight or nine cases I have done using this approach, it seems very comfortable and the patients do much better with a single incision as opposed to opening both lungs, and both chests. DR NICHOLAS T. KOUCHOUKOS (St. Louis, MO): I think certainly one can argue that that is a satisfactory alternative method. With the chronic dissections, one of the problems is really getting exposure of the intercostal arteries, which are a major source of bleeding in these patients. And if one takes the distal anastomosis quite low, one has a lot of intercostals to identify and ligate. We found that trying to get those arteries sometimes results in a lot of manipulation of the lung, and with a bilateral anterior thoracotomy, one has much clearer exposure of that area with less trauma to the lung. DR DAVID: And you have not had much pulmonary hemorrhage with retraction of the left lung? DR KOUCHOUKOS: Occasionally, if one cannot get the lung totally collapsed, one will have intraparenchymal hemorrhage on the left side; we have seen that in a couple of patients. We are very aggressive about bronchoscopy in those patients early afterwards to evacuate the clot, and certainly pulmonary complications are an important component. But my own experience with median sternotomy and even with a T incision is that you can sometimes have very limited exposure, particularly of the distal portion of the descending thoracic aorta. And in the course of trying to get good exposure, you can traumatize the lung. So we view it as a tradeoff. DR KOUCHOUKOS: We will proceed with the rest of the panel discussion. We will try to divide the time equally between the two topics that were covered this afternoon: aortic arch aneurysm and endovascular surgery. We can start with a discussion about optimal brain Ann Thorac Surg 2002;74:S1825–32 • 0003-4975/02/$22.00 PII S0003-4975(02)04262-9
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protection for operations that involve the aortic arch. Clearly, from the presentations today and from what has evolved over the last several years, there is increasing interest in the use of antegrade cerebral perfusion in contradistinction to the use (almost exclusively 5, 6, 7 years ago) of hypothermic circulatory arrest. Let me ask the panelists about their own views about this, and where they think we are heading in terms of the future. DR HAZIM J. SAFI (Houston, TX): Well, maybe it is old-fashioned, but I still use retrograde cerebral perfusion. In our hands, the incidence of neurologic deficit is really very low (in the range of 2%) and the simplicity of the procedure really helps us a lot. In the last 6 months, we have an individual, his name is Szolt (he is from Hungary) and he is an expert at transcranial Doppler. So currently we are not going with just the pressure, or a flow of less than 500 mL/min and pressure less than 25 mm Hg; we flow as much as we can: 800 or 600 mL/min, until we see reverse flow in the middle cerebral artery. My associate, Dr Tony Estrera, is going to present our results at the Key West meeting; he has about 25 patients. So I am still very pleased with retrograde cerebral perfusion with regard to early waking up. And the incidence of stroke is less. I do not know how it goes to the brain, but when I open the transverse arch, there is dark blood coming through the brachiocephalic arteries. Whether it goes through the internal jugular or whether it goes by some other method, I do not care, as long as it goes to the brain. DR KOUCHOUKOS: Do you use it continuously or intermittently? DR SAFI: I use it continuously. But what really surprised me is the use of the transcranial Doppler, which showed the reverse flow. This fellow Szolt is a very big and excitable guy; he will jump and say, “it’s a great flow,” and he can even measure the pressure in the middle cerebral artery. I am very excited about it. We have a protocol. We sent it to National Institutes of Health to fund a trial between antegrade and retrograde perfusion, and compare it to coronary artery bypass surgery and measure neurocognitive function. One reviewer said this is the best protocol since sliced bread, and the other said this is horrible. So we have to rewrite the whole protocol again. DR KOUCHOUKOS: DR Kazui, I think we know your view, but perhaps you could articulate for us what you think the role of hypothermic circulatory arrest is as the principal method of brain protection. DR TERUHISA KAZUI (Hamamatsu, Japan): On the basis of a clinical study, I am fully convinced that antegrade cerebral perfusion is the most reliable and safest method for brain protection if the protection time exceeds 30 minutes. If the expected cerebral protection time is more than 30 minutes, I think it really works. DR KOUCHOUKOS: One of the things that appears to be emerging from the evaluation of these techniques (if one looks at what was presented here and what has been published in the literature in the last several years) is that the stroke rates do not appear, at least to me, to be terribly different. Dr Kazui showed some very low stroke
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rates. But if one looks at the spectrum of publications and presentations, stroke has not been eliminated with the use of antegrade cerebral perfusion. But it appears that the incidence of temporary neurologic dysfunction is less. Dr Spielvogel, can you give us some insight as to why this might be? Your institution has looked fairly extensively at this issue. DR SPIELVOGEL: One of the things in our recent experience is that we do see the reduction of the time of circulatory arrest translated into a reduced incidence of temporary neurologic dysfunction. So the strategy (and I think we will continue in that respect) is to reduce the circulatory arrest time. If you need to do prolonged periods of reconstruction, you need to restore flow to the brain. Also, one other point is that what you see depends upon how carefully you look for temporary neurologic dysfunction. If you look very carefully at a lot of patients (even patients that have not had circulatory arrest, but have had open heart surgery) for a day or two after the surgery, they are not quite the same, and then they return to baseline. So I think that the incidence of temporary neurologic dysfunction, if you look very carefully, is probably higher than some people report. DR KOUCHOUKOS: Does anybody think there is a role for a random trial? Is it time for us to look at the patients who will not have just a short period of circulatory arrest but who will have more extensive procedures and prolonged periods? Is it worth looking at a random trial to compare these methods? DR SAFI: I strongly believe that in order really to answer the question, a randomized trial is the way to go. But it costs a lot of money, because you have to have neurocognitive testing preoperatively, and you have to try to convince a psychiatrist to work with you, and then you need a neurologist, an MRI, CAT scan, EEG preop, and postop, and 6 months later you have to analyze everything again. The patients are looking better than in the earlier era of just profound hypothermia and circulatory arrest. When I worked with my late mentor, Dr Crawford, the residents could tell us when the circulatory arrest had been greater than 40 minutes; they would tell us that the light is on and nobody is home. We do not have that syndrome any more. I think the longest period I did circulatory arrest, I did an elephant trunk in an acutely dissected aorta for a man from Greece. It took me 85 minutes to do it because I did not want to have any bleeding. And the patient (his mother tongue is not English) sent me a beautiful letter in English. So I do not know. DR KOUCHOUKOS: Let me ask Dr Mitchell and Dr Buffolo to give us their comments about the optimal method of brain protection for these extensive procedures. DR R. SCOTT MITCHELL (Stanford, CA): We have really become advocates of antegrade perfusion, and we will cannulate the axillary artery with a small 6-mm graft almost routinely for any arch work. We still are cooling patients, so we are right now using a little bit of a belt and suspenders approach. But gradually we are raising our
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CNS temperatures, and we depend upon antegrade perfusion to the extent that we will struggle to get some type of antegrade perfusion established even through a left thoracotomy. DR ENIO BUFFOLO (Sao Paulo, Spain): I am going to tell you what I do. If I think that I am able to correct aortic pathology in less than 40 minutes, like the button technique to the aortic arch, I do not use any kind of cerebral perfusion. I use retrograde perfusion when I open the aorta and find a lot of debris. So there is a mechanical reason to use retrograde perfusion. What is curious for me is that people talk about the central nervous system, and the protection is targeted to the central nervous system. You must remember that the spinal cord is also a part of the nervous system. And if you do an aortic arch reconstruction in 1 hour, or 1 hour and a half, only protecting the brain, you must remember that you have a spinal cord that must be protected too. So the way I do it is to start with the aortic arch with the technique of the auto-expandable stent in the descending aorta. Circulatory arrest lasts not more than 20 or 25 minutes, with the button technique, and then I start perfusion through the graft. And then I have all the time I need to go to the ascending aorta. DR RANDALL B. GRIEPP (New York, NY): If I may make a comment, I would like to point out that in a poster from Dr Bonser’s group in Birmingham, there is a randomized prospective study looking at retrograde cerebral perfusion, and the outcome of that study is that retrograde perfusion is associated with a higher incidence of neurologic injury. There is also a poster from Dr Ganzel from Kentucky, who has been very interested in retrograde perfusion. And in a retrospective analysis of his cases, looking at selective antegrade cerebral perfusion, hypothermia, and retrograde perfusion, he can see no favorable effect of retrograde cerebral perfusion. So there have been some prospective studies done in addition to retrospective ones. I always enjoy having my good friend, Dr Safi, here. I think he is probably the last advocate of retrograde cerebral perfusion. But, as Dr Spielvogel says, we are convinced (on the basis of laboratory and clinical data) that RCP is probably not helpful, and in some cases may be harmful. DR KOUCHOUKOS: While you are there, I want to ask you a couple of questions relating to the use of antegrade cerebral perfusion. With the subclavian technique that you mentioned and Dr Spielvogel described, do you have any concern about differential perfusion and differential cooling of the two hemispheres? There is some evidence to suggest that axillary perfusion does not cool the left brain as effectively as it does the right? Do you have any thoughts about that? DR GRIEPP: As we use the technique, all three of the brachiocephalic vessels are hooked to the common trunk and then the inflow is from the axillary artery. I think with grafts of these sizes, there is no evidence that there is diminished flow to the left side, to the left carotid or to the left subclavian. As you can see, Dr Kazui actually just clamps the left subclavian in the majority of his cases and still gets very adequate antegrade perfusion. We perfuse
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all three vessels, and I do not think there is any evidence that there is any selective flow to the right side. DR KOUCHOUKOS: The second question I have for you relates to the temperature. You use, and Dr Spielvogel described it in some detail, very profound hypothermia. Why do you need such profound hypothermia if you are using antegrade cerebral perfusion? DR Kazui uses 22°C. Why do you need to go to 10°C or 11°C? That certainly prolongs the procedure, as you pointed out. DR GRIEPP: We almost always use a period of hypothermic circulatory arrest first. In other words, with this technique, as Dr Spielvogel developed it and presented it to you this afternoon, the anastomoses of the cerebral vessels are carried out under a period of hypothermic circulatory arrest. We feel the interval of HCA is important, because the majority of those cases, as you will remember, were atherosclerotic aneurysms in older people. Those are people that have a lot of disease in the proximal vessels and so we think it is important to do all that dissection open under circulatory arrest, and then try to clean those vessels out before we restore perfusion. In younger patients in whom the vessels are normal, or are less diseased, the techniques that are used by many people involving balloon catheters (which allow you to institute selective cerebral perfusion after only a minute or two of circulatory arrest) I think will probably work fine. But I think in the majority of patients (elderly patients with atherosclerotic aneurysms), routine use of balloon catheterization of those vessels is not a good idea. So the short answer is that we have to use a period of hypothermic circulatory arrest that stretches for about 20 to 30 minutes to get those vessels off and hook them all up. Although we think that you can get by with a higher temperature, our own calculations of cerebral oxygen consumption and our own studies of the incidence of temporary neurologic dysfunction after surgery suggest that profound hypothermia is important in maintaining the cerebrum during that first 20 to 30 minutes. DR KOUCHOUKOS: Let me ask a question down the line of our panelists. What would you currently consider your safe limit for hypothermic circulatory arrest, assuming that we have used a fairly profound level of cooling? DR KAZUI: I guess a safe limit of profound hypothermia would be 30 minutes at 18°C. DR SAFI: I think with the adjunct we use, we can go up to 55 minutes. DR MITCHELL: That adjunct being retrograde perfusion? DR SAFI: Yes. DR MITCHELL: I think for just hypothermic arrest alone, it is probably temperature dependent, but I think we start almost always utilizing antegrade perfusion over about 30 minutes. DR HIDEO ADACHI (Saitami-city, Japan): I think 30 to 40 minutes is the limit. If we use hypothermic circulatory arrest, for example, in total arch replacement, I feel I have to operate myself, but if we can use selective cerebral perfusion, that is a very reliable method. So I do not need always to go to the hospital; the chief resident can safely do the total arch replacement if we can use
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selective cerebral perfusion. Of course, circulatory arrest is very useful, but selective cerebral perfusion is very reliable, and the chief resident can do it. DR SPIELVOGEL: I think that with careful planning before the surgery, you can limit your circulatory arrest times to less than 30 minutes or thereabouts. From the laboratory studies and from experience, we know that that is a good, safe period, even for elderly patients or patients with atherosclerotic disease probably involving the cerebrovascular tree. DR BUFFOLO: I would say 40 minutes at 18°C, but what is also important is the time you spend during cooling and warming. I would say that at least 40 minutes is necessary for cooling, and 50 minutes for rewarming. I had an interesting experience in a pregnant woman in whom I operated on the aortic arch with 40 minutes of total circulatory arrest; both the mother and the fetus survived, and the child was born normal. DR AKIHIKO USUI (Nagayo, Japan): We use retrograde cerebral perfusion for total arch replacement, and I think that less than 60 minutes is safe. We use the arch-first technique, just as Dr Griepp has shown, and that shortens the RCP time. DR ROBERT DION (Leiden, The Netherlands): I am very surprised that nobody mentions neuromonitoring during this type of operation. Because if you want to cool somebody, you should cool with a goal, and the goal is to achieve complete standstill of cerebral activity. We have shown in Brussels that if you do that, you have different temperatures before you can stop the circulation. It can vary from 22°C to 12°C. Another point is that even if you use cerebral perfusion, I believe that we should not only monitor the pressure and the rate of perfusion, but we should probably follow brain activity. I am quite sure that we could improve the results, which are already very good. But if you perfuse the brain at 22°C, or 25°C, perhaps sometimes you could even elevate the temperature to save time. I do not understand why nobody speaks about neuromonitoring. Is there no place for following the function of the brain? DR SAFI: I always use EEG monitoring until it is flat, and you are absolutely right. We discovered, especially with dissection, that, with flow, half of the brain sometimes is still active, whereas the other half is flat. We continue to monitor the patients until they come off the pump, and we discover that all our EEGs are not normal. But if they come back equal on both sides, none of them develop stroke. They do develop neuropsychotic problems, but I do not know whether this is true or our psychiatrists exaggerate it. (One of the psychiatrists told me that my operation is a failure because I induce pain in 100% of patients. I don’t know how to do it without causing pain). But you are absolutely right about neuromonitoring. And we are adding transcranial Doppler. We discover, especially in the elephant trunk technique, that on occasion when we deair, a pocket of air is still in the transverse arch graft, and is detected by some hit to the brain. We release the clamp and let the flow go until the
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pocket of air goes. But I think neuromonitoring is essential, and we do it in all our cases. DR JEAN BACHET (Paris, France): I use, as you may know, antegrade cerebral perfusion and I have advocated it for years, including during the previous symposium here. I now have experience in more than 200 patients, and I think there is a misunderstanding in comparing deep hypothermia, retrograde cerebral perfusion, and antegrade cerebral perfusion. This misunderstanding involves the implication that deep hypothermia is absolutely harmless. My permanent message is that one of the advantages of antegrade cerebral perfusion is that it allows one to avoid deep hypothermia. Deep hypothermia involves approximately 2 hours of useless bypass (to go down and then to go back up in temperature), and the patients then have no platelets and no fibrinogen. Whereas with antegrade cerebral perfusion, you can stop the patient at 28°C rectal; the EEG is normal after 1 hour of rewarming, and he is extubated at 6 or 8 hours after surgery. This is a great difference compared with deep hypothermia either with or without retrograde perfusion. I think it is not fair to say that those techniques are similar from a physiologic point of view. DR KOUCHOUKOS: I think there would be very little disagreement with that, with the possible exception, as several of the panelists have already mentioned, that we have to protect the spinal cord and other organs as well. I think with operations at normothermia (or even 28°C or 30°C), I would have great concern regarding the spinal cord, and I believe your previous reports have noted spinal cord ischemic injury in some of these patients. DR BACHET: Yes, we have three examples of paraplegia, but they were all in acute dissection, in patients having malperfusion. So it is very difficult to say whether it was the acute dissection or the cerebral protection system. But in elective, preoperatively normal patients, we have never seen any examples of paraparesis or paraplegia. DR AHMED RAJAII KHORASANI (Newark, NJ): I would like to make a comment, if I may. I was talking to Dr Griepp in the intermission about the lack of precision in this morning’s session about the aortic valve-sparing procedures that people talk about. I see the same thing this afternoon. There are various techniques that are all referred to as antegrade cerebral perfusion; some are axillary, some are temporary, some are undertaken after half an hour of hypothermia. I hope that gets resolved in the future, so that when we are talking about antegrade cerebral perfusion, we are all talking about the same thing. There is a physiological reason why retrograde cerebral perfusion should not be as good, and I stopped using it after I had patients with temporary neurologic deficits. The physiological and physical reason is that when you are perfusing retrograde and some of that perfusion goes to the brain, it goes to the intracranial space, which is an enclosed space. It is bone with a thick dura mater inside. As soon as the volume in an enclosed space increases, the pressure will go up. When the pressure is up, the collaterals that exist in your system (whether they go to
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the arm or to the pectoral muscle) will steal more blood. So as time goes on, there is a chance that, while it is true that there is dark blood coming out of the head vessels, and that there is reverse flow in your artery as you are monitoring it, nevertheless, the amount of flow that you are infusing is not necessarily all going to the brain. And you cannot control that. But if you have established antegrade cerebral perfusion, which is the normal way that we all have cerebral perfusion right now, that gives you perfect protection. And for me, who does probably one arch a year (I do not have a pure aortic practice), there has been really a difference of day and night. With antegrade cerebral perfusion and with deep hypothermia, the patients all do well. They wake up as though they had a coronary bypass. DR KOUCHOUKOS: I think we are all looking for the Holy Grail here, but I would caution that antegrade cerebral perfusion, from every presentation you have heard today and from what is available in the literature, does not produce a stroke-free patient population. So we still have plenty of work to do. Now, let us go on to the discussion regarding endovascular grafts. You have heard some very provocative presentations this afternoon, with some very interesting findings, both positive and negative. Let me start by questioning Dr Buffolo. His series is one of the few, at least that I am aware of, in which there has been absolutely no paraplegia. What is your explanation for the absence of paraplegia in any of your patients? This is really an extraordinary finding, I believe, and certainly is not consonant with what we have observed from other series. DR BUFFOLO: Yes, this is surprising to us. I have thought that perhaps the most important supply of blood to the spinal cord does not come through the thoracic aorta. It comes from the abdominal aorta, especially the lumbar arteries. It is hard for me to admit that there is an Adamciewicz artery. With all the experience with thoracoabdominal aneurysms, you usually do not find a huge artery that would be the radicularis magna artery. But you often see a lot of lumbar arteries. With the stents, you do not have hypotension in the abdominal aorta (it is a fast procedure) and you do not have hypotension in the proximal aorta. In the cases that I know of paraplegia with a stent in the descending aorta (I asked Dr Mitchell for confirmation) 2 of the patients had had previous abdominal surgery: infrarenal replacement of the aorta. These are patients that I am afraid of. So perhaps this is the reason why we and other series do not have an incidence of paraplegia such as you have, using a thoracoabdominal approach. DR MICHAEL L. MARIN (New York, NY): In our series, we have had 3 patients paralyzed, or with some element of paralysis after stent grafting. All 3 of them had some sort of coexisting infrarenal reconstruction. Two of them had previous infrarenal grafts placed; the devices were inserted transfemorally, and the patients developed paraplegia, which was permanent in both. In a third patient, we did an infrarenal reconstruction, placed a
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sidearm onto that graft, inserted a stent graft for a relatively focal aneurysm, and the patient was neurologically intact initially. He developed unilateral paraplegia postoperatively 12 hours after the repair, with function which returned with induced hypertension, cord drainage, and a lot of prayer. We do not have a clear answer as to why these people have paraplegia, and I am not sure it is just because the lumbars are the source, since we take all the lumbars routinely when we do an infrarenal repair. It is some combination of losing the thoracic or intercostals together with the lumbars, and perhaps something to do with the internal iliac supply as well. DR MITCHELL: I agree with all those comments. We have seen the same thing: three instances of paraplegia, two with simultaneous abdominal aortic aneurysm repair and one with a previous aneurysm repair, and we have not seen it in the absence of abdominal aortic problems. So I think there probably is a fairly extensive collateral network from hypogastrics, lumbars, and intercostals, and probably the patients most at risk are those who need aneurysms fixed in both locales. DR MARIN: Just a comment. We also have 13 patients with combined aneurysms that we have done and we have not seen paralysis. So it is not a given. What we do is we put a spinal cord drain in all of those patients who have had previous infrarenal repairs in whom we contemplate doing a thoracic reconstruction, and it seems not to be inevitable that they will develop paraplegia in that setting. DR SAFI: That is true in our experience when we replace the extent I thoracoabdominal with the infrarenal aorta. In the era of clamp and go, however, infrarenal abdominal aortic aneurysm was a risk factor for development of neurologic deficits, to our surprise. DR KOUCHOUKOS: Dr Marin, you mentioned fracture of the wires in these endovascular grafts. Can you tell us about the fabrics? Have there not been tears in the fabrics of the abdominal grafts? DR MARIN: This is the one concern (or the greatest concern) people have, because we have not been able to demonstrate an obvious follow-up problem associated with just strut or wire fracture alone. Intuitively, once the wire fractures occur, you have will have sharp edges of the wire, which will be grating or rubbing on the prosthesis, and wear or tear can potentially occur. Whereas there have been multiple instances where people have explanted grafts that have shown wear in the fabric that actually perforated and communicated with the aneurysm sac, no one has yet confirmed a case where aneurysm enlargement or rupture was caused by this problem. But the concern is large enough to have caused that device, the Gore device, to be withdrawn. Because of concern of fabric wear and tear, the construction of existing devices has been such that fracture has been reduced to a minimum, and securing the prosthesis to the stent has been increased to prevent any micromotion. DR KOUCHOUKOS: Dr Mitchell, any comments about that? DR MITCHELL: Well, it is a concern. We have not seen associated patient events with documented fractures, but
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it is pretty clear that the fabric and the metal are closely associated, and it likely will happen. It is an ongoing problem, because we would like to have a very low profile device, which unfortunately then mandates a very thin-walled graft material, which is obviously going to be more subject to wear and tear. And it may be that we are going to see a lot of these micro leaks as these grafts get out a few years. There are real concerns about the long-term durability of all these very ultrathin grafts that are being used. DR KOUCHOUKOS: One of the criticisms that has been leveled at abdominal endovascular grafting is that patients are being subjected to or are undergoing these procedures who may not need them. In other words, there is a tendency to place these endografts into patients with smaller aneurysms, in which the risk of rupture is extremely low, and there have been editorials critical of this approach. Is it conceivable that the same thing could happen in the thoracic aorta? In other words, just because an aneurysm is there and because it is 4 cm, should we obliterate it with an endovascular graft? One of the reasons I bring it up is that, for example, in Dr Buffolo’s series, the largest percentage of patients in whom he has inserted grafts have been patients with type B dissections. Many of those patients, at least in our country, are not treated with any surgical intervention. They are treated medically. So are we now creating another population of patients in whom we are going to apply an intervention where, at least in the past, there has not been any need for an intervention? DR MITCHELL: I think some of my comments were directed exactly at that possibility. As you travel around the world, in various locales, there is a great enthusiasm for these endografts. And clearly, unless somehow regulated, I think there would be a lot of use that would not be necessary. So we have tried to encourage, certainly in our own experience, use of grafts only for patients who truly exhibit surgical indications, both for dissections and aneurysms. I feel strongly that until we have more data, endograft use should be limited to those patients. DR MARIN: I cannot dispute that; I think that is correct, but I think the fear is greater than the actual event. I think the number of patients who have the kind of choice, small lesions that are amenable to this type of prosthesis is very limited. The patient with a small penetrating ulcer that may be ideal, or the relatively small fusiform aneurysm that has a good neck proximally and distally, is just not that common in most practices. What is common are patients with disease that extends to the visceral segment or more proximally to the arch, and in that setting, maybe some combined procedure does make sense, but not in patients with aneurysms smaller than would represent surgical indications. I think we are pretty comfortable with that approach, and that is what drives usage in most centers of excellence. DR KOUCHOUKOS: Dr Buffolo, can you comment on the high prevalence of aortic dissections in your series? DR BUFFOLO: First of all, for the abdominal aneurysms, I think that the results are worse than for thoracic. This is our experience. The endoleak is more common in
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aneurysms of the abdominal aorta. And I still think that the five-star treatment of the AAA is conventional surgical correction. We use the endovascular approach for patients with comorbidities, very important comorbidities. That is our position regarding the abdominal aorta. So this is not the situation you are concerned about But for type B dissection, we have a different opinion. We started our experience with a complicated case, and now at this moment we treat acute cases even without complications. Why? Because in following up these patients in outpatient care you will see acquired pathology. There is a reentry tear usually at the level of the left renal artery, or the left iliac artery. So you develop a condition in which a stent in the patient is no longer possible. So in these kinds of patients, in a few years, you will have to do a thoracoabdominal approach. So, at this moment, if you see acute cases of type B dissection, the pathology is only a tear just distal to the left subclavian artery, and this is a very simple condition to treat with a stent. The best results we have are in type B acute dissections and penetrating ulcers. I presented the overall mortality 5 years ago, and it was 10%. But if I could present the mortality in the uncomplicated cases (I thought it was not fair to present those numbers), it would be better. But if you consider the mortality in the most recent 2 years, it is almost 0%. With this in view, in type B dissection, we prefer to treat these patients in the acute phase. With this approach you do not have acquired pathology. DR MARIN: I think there are distinctions between the types of practices people have and the patients they are seeing, because we just do not see patients like that. I see about two to three type B dissections, both acute and chronic, a week, and I cannot remember the last time I saw one where there was just an isolated tear in one segment just distal to the subclavian, and that was the only entry point. The ones that are referred to our group tend to have multiple entry and exit points. And when we have attempted to stent the chronic ones, they have had the highest failure rate in our hands. We can seal the upper tear or seal several of the dissection planes, but they always reenter somewhere below and then somehow find a way to communicate with the original channel. We just do not see those that have that single tear right at the left subclavian, which I agree would be ideal candidates for stent grafting. DR KOUCHOUKOS: In the few minutes remaining, let me just address one other issue: the branch grafts. We have seen some very interesting videos and angiograms this afternoon about the use of these grafts, and also we saw some information from the presentations that the embolic rate is not inconsequential. How are we going to deal with this problem in the future? To me, placing these endovascular grafts into potentially severely atherosclerotic subclavian, carotid, renal, and visceral vessels makes chills run up and down my spine. Maybe I am just overreacting, but I really have concern about this. Clearly, this problem has to be resolved. How are we going to resolve it? We saw some filters used, but that certainly would add to the complexity of the procedures.
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So let me ask Dr Hosokawa and Dr Usui to comment on that, because they made these presentations. DR KAZUI: Every surgeon knows what the aortic arch looks like when you do open surgery. There is a lot of atheroma around the orifices of the arch vessels. So I am afraid if you put a catheter through the arch vessels in doing the stent graft, this may cause a high incidence of stroke. I would hate to do this kind of a procedure, particularly in the case of an atherosclerotic arch aneurysm. I probably feel the same way about thoracoabdominal aortic aneurysms, too. DR HIROAKI HOSOKAWA (Toyohashi, Japan): In our experience, the three-branched stent graft has a high incidence of brain thrombosis, and now we are developing a detachable filter device to prevent distal embolism. And it seems to be working, but it is time-consuming and sometimes it is difficult to retrieve through the stent graft. We need more experience using this kind of device. DR MARIN: I spent the past 6 years trying to develop a commercially available branch endograft, and I am quite confident that at Aortic Symposium IX, in the United States, we will not have a branch graft for the arch or the visceral segment. The number of patients who will fit the strict anatomic criteria is so small that there is not an industry in America that would be willing to take on the clinical trials and the complexity to develop the technology. DR SAFI: I second your fear from these branch grafts, Dr Kouchoukos. And we always, as my friend, Scott Mitchell, said, have to be diligent in our follow-up of these patients. In the recent study by the VA of the natural history of infrarenal abdominal aortic aneurysms 5 cm and less, the incidence of rupture is 1% per patient per year. Whereas in a modular graft in the infrarenal position, the incidence of rupture in the treated group was 1.5 patients per year. So we have to be careful about all these things. If I have an infrarenal abdominal aortic aneurysm, do I want to have a CAT scan every 3 months? Rather, I will go to a good surgeon who can do it with less than a 2% mortality rate, and with Viagra available, you do not need to worry about the pelvic nerves. DR MICHAEL JACOBS (Maastricht, The Netherlands): One of the advantages of a collective data bank, as we have in Europe (like EuroSCORE), is that it keeps us awake and alert. Like everybody else, we do 15 or 20 thoracic aortic aneurysms by means of endografting, but these collective data banks really show us the figures. And I can tell you that the data we have in Europe show a considerably higher incidence of paraplegia, renal failure, and mortality than we heard today. One of the complications I did not hear about this afternoon is what we observed during the last 3 months in our own hospital. We inserted a perfectly positioned endograft for an acute type B dissection; the indications for treatment were ischemic problems, renal insufficiency, a dead leg, and even rupture. Despite the perfect position, in 3 patients during the last month, this type B dissection (in 1 patient within 2 days, another within a week, and a third within 4 weeks) retrogradely involved
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the aortic arch and turned a type B dissection into an acute type A dissection, requiring acute arch replacement. I wonder whether the panel surgeons have also experienced this dramatic complication. Because I can tell you it is no fun in the middle of the night to open up an aortic arch, and deep in the proximal descending you see that fixed graft, which you cannot get out unless you use a metal scissors. You feel very strange during that procedure to have to tear that thing out and then replace the arch. Have you ever experienced that? DR SAFI: I had experience with one we were following with a type B dissection treated medically. He saw his friend, a gastroenterologist, who gave him Maalox and sent him home. And a week later he came and did an arteriogram (he is an interventional radiologist), and at noontime he was found dead. Luckily somehow we revived him. The antegrade dissection does happen, even spontaneously, but the problem of removing unsuccessful endografts is an important issue. In the last 5 years I have removed at least 20 grafts inserted either in the infrarenal or in the descending thoracic aorta. It is a mess if you do not open the aorta and remove them. In the infrarenal abdominal aorta, you cannot do it with the anchoring devices located above the renal arteries, short of a thoracoabdominal incision, because if you try to pull the graft out, you will rip everything off. We have a cardiologist now in our institution, who, when I first went there about 2 and a half years ago, had a coil for infrarenal abdominal aortic aneurysm. And he wanted me to be a coinvestigator. I told him this was tried in the 1930s, and they even put in some kind of wire and with electricity clotted it. Why does he have to repeat that? And he has 20 cases! I have operated on 10 of them in more than 3 years. All of those cases were billed as inoperable and then 2 or 3 years later they became operable. DR MARIN: We published our series of 9 patients who had infrarenal aneurysms with proximal thoracic dissections. The proximal dissections were small, and these were sick patients. Of the 9, we had 1 patient in whom we placed a stent graft sealing the distal exit point of the infrarenal aneurysm, which resulted in a more broad dissection retrograde and enlargement of the thoracic dissection such that he required thoracic reconstruction and succumbed to that. So the placement of stents in the dissected plane can result in retrograde dissection and can result in enlargement. A potential small tear that may have been there may enlarge significantly once the outflow tract or the distal dissection is sealed. DR BUFFOLO: I would like to ask a question of Dr Jacobs. What kind of stent do you use: auto-expandable or balloon-expandable? DR JACOBS: This was just a regular Talent stent that we positioned over the left subclavian covering the tear. DR BUFFOLO: But is it balloon-expandable or auto-expandable? DR JACOBS: Auto-expandable. DR BUFFOLO: Because this happens with balloonexpandable stents.
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DR JACOBS: Yes, sure. DR JEAN-PIERRE NORMAND (Quebec, Canada): I have two questions. First, in a patient with a very short neck between the left subclavian artery and the aneurysm, what do you suggest: a preop bypass, a stent with one branch, or a late bypass if the patient has symptoms? And a second question. Do you assess the vertebral arteries before stent grafting? DR MARIN: We do a transposition or a bypass. The procedure is benign enough and simple enough that if a patient is too sick to undergo a carotid-subclavian transposition, you have to really question whether or not fixing their aneurysm is worthwhile in terms of longevity. Whether the transposition has to be done or not is a question, because there are many people publishing series where they do not do it and they just cover the subclavian routinely without difficulty. I suppose that could be done, but it is simple enough to do the transposition. Transposition maintains perfusion to the vertebral, which may in some fashion, along with the other collaterals from the subclavian, contribute to spinal cord circulation, and we routinely will do the transposition. And if the neck is short, as you asked in the first question,
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we always do it. Because even if you could sneak a stent graft in with a relatively short neck, you can end up with a good cosmetic result at the completion of the procedure and then give Dr Safi plenty of work to do later and complain about, because the patient will come back in 6 months with a failure. DR BUFFOLO: We had 14 cases of intentional occlusion of the left subclavian artery, and in only one case was it necessary in the late follow-up to create a shunt. Nothing happens. But the problem is not this. The problem is the danger of occluding the left carotid artery that in some cases is very close to the left subclavian artery. For these situations, we prefer to do endoscopy with a special program called the Navigator; you do a real aortoscopy noninvasively. If there is some doubt that occlusion of the left subclavian artery by the stent can compromise the origin of the left carotid, this is not a suitable indication for a stent. This is an indication for an open approach through the aortic arch. DR KOUCHOUKOS: Thank you. Our time is up. I want to thank the panelists and the audience for their participation.
© 2002 by The Society of Thoracic Surgeons Published by Elsevier Science Inc
ascending aorta, you should replace just the ascending aorta, but if the tear is in the arch, this technique certainly is an option. DR TIRONE DAVID (Toronto, Ontario, Canada): A question for Dr Kouchoukos and Dr Safi. Why not do a sternotomy in a single stage? In other words, do your arch operation, lift the heart, open the posterior pericardium, and that is where the descending thoracic aorta is. You do not have any retraction of the lungs, you do not have to do anything. Staple the aorta proximally and distally. I have not done as large a number as you, but in the eight or nine cases I have done using this approach, it seems very comfortable and the patients do much better with a single incision as opposed to opening both lungs, and both chests. DR NICHOLAS T. KOUCHOUKOS (St. Louis, MO): I think certainly one can argue that that is a satisfactory alternative method. With the chronic dissections, one of the problems is really getting exposure of the intercostal arteries, which are a major source of bleeding in these patients. And if one takes the distal anastomosis quite low, one has a lot of intercostals to identify and ligate. We found that trying to get those arteries sometimes results in a lot of manipulation of the lung, and with a bilateral anterior thoracotomy, one has much clearer exposure of that area with less trauma to the lung. DR DAVID: And you have not had much pulmonary hemorrhage with retraction of the left lung? DR KOUCHOUKOS: Occasionally, if one cannot get the lung totally collapsed, one will have intraparenchymal hemorrhage on the left side; we have seen that in a couple of patients. We are very aggressive about bronchoscopy in those patients early afterwards to evacuate the clot, and certainly pulmonary complications are an important component. But my own experience with median sternotomy and even with a T incision is that you can sometimes have very limited exposure, particularly of the distal portion of the descending thoracic aorta. And in the course of trying to get good exposure, you can traumatize the lung. So we view it as a tradeoff. DR KOUCHOUKOS: We will proceed with the rest of the panel discussion. We will try to divide the time equally between the two topics that were covered this afternoon: aortic arch aneurysm and endovascular surgery. We can start with a discussion about optimal brain Ann Thorac Surg 2002;74:S1825–32 • 0003-4975/02/$22.00 PII S0003-4975(02)04262-9
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protection for operations that involve the aortic arch. Clearly, from the presentations today and from what has evolved over the last several years, there is increasing interest in the use of antegrade cerebral perfusion in contradistinction to the use (almost exclusively 5, 6, 7 years ago) of hypothermic circulatory arrest. Let me ask the panelists about their own views about this, and where they think we are heading in terms of the future. DR HAZIM J. SAFI (Houston, TX): Well, maybe it is old-fashioned, but I still use retrograde cerebral perfusion. In our hands, the incidence of neurologic deficit is really very low (in the range of 2%) and the simplicity of the procedure really helps us a lot. In the last 6 months, we have an individual, his name is Szolt (he is from Hungary) and he is an expert at transcranial Doppler. So currently we are not going with just the pressure, or a flow of less than 500 mL/min and pressure less than 25 mm Hg; we flow as much as we can: 800 or 600 mL/min, until we see reverse flow in the middle cerebral artery. My associate, Dr Tony Estrera, is going to present our results at the Key West meeting; he has about 25 patients. So I am still very pleased with retrograde cerebral perfusion with regard to early waking up. And the incidence of stroke is less. I do not know how it goes to the brain, but when I open the transverse arch, there is dark blood coming through the brachiocephalic arteries. Whether it goes through the internal jugular or whether it goes by some other method, I do not care, as long as it goes to the brain. DR KOUCHOUKOS: Do you use it continuously or intermittently? DR SAFI: I use it continuously. But what really surprised me is the use of the transcranial Doppler, which showed the reverse flow. This fellow Szolt is a very big and excitable guy; he will jump and say, “it’s a great flow,” and he can even measure the pressure in the middle cerebral artery. I am very excited about it. We have a protocol. We sent it to National Institutes of Health to fund a trial between antegrade and retrograde perfusion, and compare it to coronary artery bypass surgery and measure neurocognitive function. One reviewer said this is the best protocol since sliced bread, and the other said this is horrible. So we have to rewrite the whole protocol again. DR KOUCHOUKOS: DR Kazui, I think we know your view, but perhaps you could articulate for us what you think the role of hypothermic circulatory arrest is as the principal method of brain protection. DR TERUHISA KAZUI (Hamamatsu, Japan): On the basis of a clinical study, I am fully convinced that antegrade cerebral perfusion is the most reliable and safest method for brain protection if the protection time exceeds 30 minutes. If the expected cerebral protection time is more than 30 minutes, I think it really works. DR KOUCHOUKOS: One of the things that appears to be emerging from the evaluation of these techniques (if one looks at what was presented here and what has been published in the literature in the last several years) is that the stroke rates do not appear, at least to me, to be terribly different. Dr Kazui showed some very low stroke
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rates. But if one looks at the spectrum of publications and presentations, stroke has not been eliminated with the use of antegrade cerebral perfusion. But it appears that the incidence of temporary neurologic dysfunction is less. Dr Spielvogel, can you give us some insight as to why this might be? Your institution has looked fairly extensively at this issue. DR SPIELVOGEL: One of the things in our recent experience is that we do see the reduction of the time of circulatory arrest translated into a reduced incidence of temporary neurologic dysfunction. So the strategy (and I think we will continue in that respect) is to reduce the circulatory arrest time. If you need to do prolonged periods of reconstruction, you need to restore flow to the brain. Also, one other point is that what you see depends upon how carefully you look for temporary neurologic dysfunction. If you look very carefully at a lot of patients (even patients that have not had circulatory arrest, but have had open heart surgery) for a day or two after the surgery, they are not quite the same, and then they return to baseline. So I think that the incidence of temporary neurologic dysfunction, if you look very carefully, is probably higher than some people report. DR KOUCHOUKOS: Does anybody think there is a role for a random trial? Is it time for us to look at the patients who will not have just a short period of circulatory arrest but who will have more extensive procedures and prolonged periods? Is it worth looking at a random trial to compare these methods? DR SAFI: I strongly believe that in order really to answer the question, a randomized trial is the way to go. But it costs a lot of money, because you have to have neurocognitive testing preoperatively, and you have to try to convince a psychiatrist to work with you, and then you need a neurologist, an MRI, CAT scan, EEG preop, and postop, and 6 months later you have to analyze everything again. The patients are looking better than in the earlier era of just profound hypothermia and circulatory arrest. When I worked with my late mentor, Dr Crawford, the residents could tell us when the circulatory arrest had been greater than 40 minutes; they would tell us that the light is on and nobody is home. We do not have that syndrome any more. I think the longest period I did circulatory arrest, I did an elephant trunk in an acutely dissected aorta for a man from Greece. It took me 85 minutes to do it because I did not want to have any bleeding. And the patient (his mother tongue is not English) sent me a beautiful letter in English. So I do not know. DR KOUCHOUKOS: Let me ask Dr Mitchell and Dr Buffolo to give us their comments about the optimal method of brain protection for these extensive procedures. DR R. SCOTT MITCHELL (Stanford, CA): We have really become advocates of antegrade perfusion, and we will cannulate the axillary artery with a small 6-mm graft almost routinely for any arch work. We still are cooling patients, so we are right now using a little bit of a belt and suspenders approach. But gradually we are raising our
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CNS temperatures, and we depend upon antegrade perfusion to the extent that we will struggle to get some type of antegrade perfusion established even through a left thoracotomy. DR ENIO BUFFOLO (Sao Paulo, Spain): I am going to tell you what I do. If I think that I am able to correct aortic pathology in less than 40 minutes, like the button technique to the aortic arch, I do not use any kind of cerebral perfusion. I use retrograde perfusion when I open the aorta and find a lot of debris. So there is a mechanical reason to use retrograde perfusion. What is curious for me is that people talk about the central nervous system, and the protection is targeted to the central nervous system. You must remember that the spinal cord is also a part of the nervous system. And if you do an aortic arch reconstruction in 1 hour, or 1 hour and a half, only protecting the brain, you must remember that you have a spinal cord that must be protected too. So the way I do it is to start with the aortic arch with the technique of the auto-expandable stent in the descending aorta. Circulatory arrest lasts not more than 20 or 25 minutes, with the button technique, and then I start perfusion through the graft. And then I have all the time I need to go to the ascending aorta. DR RANDALL B. GRIEPP (New York, NY): If I may make a comment, I would like to point out that in a poster from Dr Bonser’s group in Birmingham, there is a randomized prospective study looking at retrograde cerebral perfusion, and the outcome of that study is that retrograde perfusion is associated with a higher incidence of neurologic injury. There is also a poster from Dr Ganzel from Kentucky, who has been very interested in retrograde perfusion. And in a retrospective analysis of his cases, looking at selective antegrade cerebral perfusion, hypothermia, and retrograde perfusion, he can see no favorable effect of retrograde cerebral perfusion. So there have been some prospective studies done in addition to retrospective ones. I always enjoy having my good friend, Dr Safi, here. I think he is probably the last advocate of retrograde cerebral perfusion. But, as Dr Spielvogel says, we are convinced (on the basis of laboratory and clinical data) that RCP is probably not helpful, and in some cases may be harmful. DR KOUCHOUKOS: While you are there, I want to ask you a couple of questions relating to the use of antegrade cerebral perfusion. With the subclavian technique that you mentioned and Dr Spielvogel described, do you have any concern about differential perfusion and differential cooling of the two hemispheres? There is some evidence to suggest that axillary perfusion does not cool the left brain as effectively as it does the right? Do you have any thoughts about that? DR GRIEPP: As we use the technique, all three of the brachiocephalic vessels are hooked to the common trunk and then the inflow is from the axillary artery. I think with grafts of these sizes, there is no evidence that there is diminished flow to the left side, to the left carotid or to the left subclavian. As you can see, Dr Kazui actually just clamps the left subclavian in the majority of his cases and still gets very adequate antegrade perfusion. We perfuse
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all three vessels, and I do not think there is any evidence that there is any selective flow to the right side. DR KOUCHOUKOS: The second question I have for you relates to the temperature. You use, and Dr Spielvogel described it in some detail, very profound hypothermia. Why do you need such profound hypothermia if you are using antegrade cerebral perfusion? DR Kazui uses 22°C. Why do you need to go to 10°C or 11°C? That certainly prolongs the procedure, as you pointed out. DR GRIEPP: We almost always use a period of hypothermic circulatory arrest first. In other words, with this technique, as Dr Spielvogel developed it and presented it to you this afternoon, the anastomoses of the cerebral vessels are carried out under a period of hypothermic circulatory arrest. We feel the interval of HCA is important, because the majority of those cases, as you will remember, were atherosclerotic aneurysms in older people. Those are people that have a lot of disease in the proximal vessels and so we think it is important to do all that dissection open under circulatory arrest, and then try to clean those vessels out before we restore perfusion. In younger patients in whom the vessels are normal, or are less diseased, the techniques that are used by many people involving balloon catheters (which allow you to institute selective cerebral perfusion after only a minute or two of circulatory arrest) I think will probably work fine. But I think in the majority of patients (elderly patients with atherosclerotic aneurysms), routine use of balloon catheterization of those vessels is not a good idea. So the short answer is that we have to use a period of hypothermic circulatory arrest that stretches for about 20 to 30 minutes to get those vessels off and hook them all up. Although we think that you can get by with a higher temperature, our own calculations of cerebral oxygen consumption and our own studies of the incidence of temporary neurologic dysfunction after surgery suggest that profound hypothermia is important in maintaining the cerebrum during that first 20 to 30 minutes. DR KOUCHOUKOS: Let me ask a question down the line of our panelists. What would you currently consider your safe limit for hypothermic circulatory arrest, assuming that we have used a fairly profound level of cooling? DR KAZUI: I guess a safe limit of profound hypothermia would be 30 minutes at 18°C. DR SAFI: I think with the adjunct we use, we can go up to 55 minutes. DR MITCHELL: That adjunct being retrograde perfusion? DR SAFI: Yes. DR MITCHELL: I think for just hypothermic arrest alone, it is probably temperature dependent, but I think we start almost always utilizing antegrade perfusion over about 30 minutes. DR HIDEO ADACHI (Saitami-city, Japan): I think 30 to 40 minutes is the limit. If we use hypothermic circulatory arrest, for example, in total arch replacement, I feel I have to operate myself, but if we can use selective cerebral perfusion, that is a very reliable method. So I do not need always to go to the hospital; the chief resident can safely do the total arch replacement if we can use
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selective cerebral perfusion. Of course, circulatory arrest is very useful, but selective cerebral perfusion is very reliable, and the chief resident can do it. DR SPIELVOGEL: I think that with careful planning before the surgery, you can limit your circulatory arrest times to less than 30 minutes or thereabouts. From the laboratory studies and from experience, we know that that is a good, safe period, even for elderly patients or patients with atherosclerotic disease probably involving the cerebrovascular tree. DR BUFFOLO: I would say 40 minutes at 18°C, but what is also important is the time you spend during cooling and warming. I would say that at least 40 minutes is necessary for cooling, and 50 minutes for rewarming. I had an interesting experience in a pregnant woman in whom I operated on the aortic arch with 40 minutes of total circulatory arrest; both the mother and the fetus survived, and the child was born normal. DR AKIHIKO USUI (Nagayo, Japan): We use retrograde cerebral perfusion for total arch replacement, and I think that less than 60 minutes is safe. We use the arch-first technique, just as Dr Griepp has shown, and that shortens the RCP time. DR ROBERT DION (Leiden, The Netherlands): I am very surprised that nobody mentions neuromonitoring during this type of operation. Because if you want to cool somebody, you should cool with a goal, and the goal is to achieve complete standstill of cerebral activity. We have shown in Brussels that if you do that, you have different temperatures before you can stop the circulation. It can vary from 22°C to 12°C. Another point is that even if you use cerebral perfusion, I believe that we should not only monitor the pressure and the rate of perfusion, but we should probably follow brain activity. I am quite sure that we could improve the results, which are already very good. But if you perfuse the brain at 22°C, or 25°C, perhaps sometimes you could even elevate the temperature to save time. I do not understand why nobody speaks about neuromonitoring. Is there no place for following the function of the brain? DR SAFI: I always use EEG monitoring until it is flat, and you are absolutely right. We discovered, especially with dissection, that, with flow, half of the brain sometimes is still active, whereas the other half is flat. We continue to monitor the patients until they come off the pump, and we discover that all our EEGs are not normal. But if they come back equal on both sides, none of them develop stroke. They do develop neuropsychotic problems, but I do not know whether this is true or our psychiatrists exaggerate it. (One of the psychiatrists told me that my operation is a failure because I induce pain in 100% of patients. I don’t know how to do it without causing pain). But you are absolutely right about neuromonitoring. And we are adding transcranial Doppler. We discover, especially in the elephant trunk technique, that on occasion when we deair, a pocket of air is still in the transverse arch graft, and is detected by some hit to the brain. We release the clamp and let the flow go until the
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pocket of air goes. But I think neuromonitoring is essential, and we do it in all our cases. DR JEAN BACHET (Paris, France): I use, as you may know, antegrade cerebral perfusion and I have advocated it for years, including during the previous symposium here. I now have experience in more than 200 patients, and I think there is a misunderstanding in comparing deep hypothermia, retrograde cerebral perfusion, and antegrade cerebral perfusion. This misunderstanding involves the implication that deep hypothermia is absolutely harmless. My permanent message is that one of the advantages of antegrade cerebral perfusion is that it allows one to avoid deep hypothermia. Deep hypothermia involves approximately 2 hours of useless bypass (to go down and then to go back up in temperature), and the patients then have no platelets and no fibrinogen. Whereas with antegrade cerebral perfusion, you can stop the patient at 28°C rectal; the EEG is normal after 1 hour of rewarming, and he is extubated at 6 or 8 hours after surgery. This is a great difference compared with deep hypothermia either with or without retrograde perfusion. I think it is not fair to say that those techniques are similar from a physiologic point of view. DR KOUCHOUKOS: I think there would be very little disagreement with that, with the possible exception, as several of the panelists have already mentioned, that we have to protect the spinal cord and other organs as well. I think with operations at normothermia (or even 28°C or 30°C), I would have great concern regarding the spinal cord, and I believe your previous reports have noted spinal cord ischemic injury in some of these patients. DR BACHET: Yes, we have three examples of paraplegia, but they were all in acute dissection, in patients having malperfusion. So it is very difficult to say whether it was the acute dissection or the cerebral protection system. But in elective, preoperatively normal patients, we have never seen any examples of paraparesis or paraplegia. DR AHMED RAJAII KHORASANI (Newark, NJ): I would like to make a comment, if I may. I was talking to Dr Griepp in the intermission about the lack of precision in this morning’s session about the aortic valve-sparing procedures that people talk about. I see the same thing this afternoon. There are various techniques that are all referred to as antegrade cerebral perfusion; some are axillary, some are temporary, some are undertaken after half an hour of hypothermia. I hope that gets resolved in the future, so that when we are talking about antegrade cerebral perfusion, we are all talking about the same thing. There is a physiological reason why retrograde cerebral perfusion should not be as good, and I stopped using it after I had patients with temporary neurologic deficits. The physiological and physical reason is that when you are perfusing retrograde and some of that perfusion goes to the brain, it goes to the intracranial space, which is an enclosed space. It is bone with a thick dura mater inside. As soon as the volume in an enclosed space increases, the pressure will go up. When the pressure is up, the collaterals that exist in your system (whether they go to
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the arm or to the pectoral muscle) will steal more blood. So as time goes on, there is a chance that, while it is true that there is dark blood coming out of the head vessels, and that there is reverse flow in your artery as you are monitoring it, nevertheless, the amount of flow that you are infusing is not necessarily all going to the brain. And you cannot control that. But if you have established antegrade cerebral perfusion, which is the normal way that we all have cerebral perfusion right now, that gives you perfect protection. And for me, who does probably one arch a year (I do not have a pure aortic practice), there has been really a difference of day and night. With antegrade cerebral perfusion and with deep hypothermia, the patients all do well. They wake up as though they had a coronary bypass. DR KOUCHOUKOS: I think we are all looking for the Holy Grail here, but I would caution that antegrade cerebral perfusion, from every presentation you have heard today and from what is available in the literature, does not produce a stroke-free patient population. So we still have plenty of work to do. Now, let us go on to the discussion regarding endovascular grafts. You have heard some very provocative presentations this afternoon, with some very interesting findings, both positive and negative. Let me start by questioning Dr Buffolo. His series is one of the few, at least that I am aware of, in which there has been absolutely no paraplegia. What is your explanation for the absence of paraplegia in any of your patients? This is really an extraordinary finding, I believe, and certainly is not consonant with what we have observed from other series. DR BUFFOLO: Yes, this is surprising to us. I have thought that perhaps the most important supply of blood to the spinal cord does not come through the thoracic aorta. It comes from the abdominal aorta, especially the lumbar arteries. It is hard for me to admit that there is an Adamciewicz artery. With all the experience with thoracoabdominal aneurysms, you usually do not find a huge artery that would be the radicularis magna artery. But you often see a lot of lumbar arteries. With the stents, you do not have hypotension in the abdominal aorta (it is a fast procedure) and you do not have hypotension in the proximal aorta. In the cases that I know of paraplegia with a stent in the descending aorta (I asked Dr Mitchell for confirmation) 2 of the patients had had previous abdominal surgery: infrarenal replacement of the aorta. These are patients that I am afraid of. So perhaps this is the reason why we and other series do not have an incidence of paraplegia such as you have, using a thoracoabdominal approach. DR MICHAEL L. MARIN (New York, NY): In our series, we have had 3 patients paralyzed, or with some element of paralysis after stent grafting. All 3 of them had some sort of coexisting infrarenal reconstruction. Two of them had previous infrarenal grafts placed; the devices were inserted transfemorally, and the patients developed paraplegia, which was permanent in both. In a third patient, we did an infrarenal reconstruction, placed a
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sidearm onto that graft, inserted a stent graft for a relatively focal aneurysm, and the patient was neurologically intact initially. He developed unilateral paraplegia postoperatively 12 hours after the repair, with function which returned with induced hypertension, cord drainage, and a lot of prayer. We do not have a clear answer as to why these people have paraplegia, and I am not sure it is just because the lumbars are the source, since we take all the lumbars routinely when we do an infrarenal repair. It is some combination of losing the thoracic or intercostals together with the lumbars, and perhaps something to do with the internal iliac supply as well. DR MITCHELL: I agree with all those comments. We have seen the same thing: three instances of paraplegia, two with simultaneous abdominal aortic aneurysm repair and one with a previous aneurysm repair, and we have not seen it in the absence of abdominal aortic problems. So I think there probably is a fairly extensive collateral network from hypogastrics, lumbars, and intercostals, and probably the patients most at risk are those who need aneurysms fixed in both locales. DR MARIN: Just a comment. We also have 13 patients with combined aneurysms that we have done and we have not seen paralysis. So it is not a given. What we do is we put a spinal cord drain in all of those patients who have had previous infrarenal repairs in whom we contemplate doing a thoracic reconstruction, and it seems not to be inevitable that they will develop paraplegia in that setting. DR SAFI: That is true in our experience when we replace the extent I thoracoabdominal with the infrarenal aorta. In the era of clamp and go, however, infrarenal abdominal aortic aneurysm was a risk factor for development of neurologic deficits, to our surprise. DR KOUCHOUKOS: Dr Marin, you mentioned fracture of the wires in these endovascular grafts. Can you tell us about the fabrics? Have there not been tears in the fabrics of the abdominal grafts? DR MARIN: This is the one concern (or the greatest concern) people have, because we have not been able to demonstrate an obvious follow-up problem associated with just strut or wire fracture alone. Intuitively, once the wire fractures occur, you have will have sharp edges of the wire, which will be grating or rubbing on the prosthesis, and wear or tear can potentially occur. Whereas there have been multiple instances where people have explanted grafts that have shown wear in the fabric that actually perforated and communicated with the aneurysm sac, no one has yet confirmed a case where aneurysm enlargement or rupture was caused by this problem. But the concern is large enough to have caused that device, the Gore device, to be withdrawn. Because of concern of fabric wear and tear, the construction of existing devices has been such that fracture has been reduced to a minimum, and securing the prosthesis to the stent has been increased to prevent any micromotion. DR KOUCHOUKOS: Dr Mitchell, any comments about that? DR MITCHELL: Well, it is a concern. We have not seen associated patient events with documented fractures, but
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it is pretty clear that the fabric and the metal are closely associated, and it likely will happen. It is an ongoing problem, because we would like to have a very low profile device, which unfortunately then mandates a very thin-walled graft material, which is obviously going to be more subject to wear and tear. And it may be that we are going to see a lot of these micro leaks as these grafts get out a few years. There are real concerns about the long-term durability of all these very ultrathin grafts that are being used. DR KOUCHOUKOS: One of the criticisms that has been leveled at abdominal endovascular grafting is that patients are being subjected to or are undergoing these procedures who may not need them. In other words, there is a tendency to place these endografts into patients with smaller aneurysms, in which the risk of rupture is extremely low, and there have been editorials critical of this approach. Is it conceivable that the same thing could happen in the thoracic aorta? In other words, just because an aneurysm is there and because it is 4 cm, should we obliterate it with an endovascular graft? One of the reasons I bring it up is that, for example, in Dr Buffolo’s series, the largest percentage of patients in whom he has inserted grafts have been patients with type B dissections. Many of those patients, at least in our country, are not treated with any surgical intervention. They are treated medically. So are we now creating another population of patients in whom we are going to apply an intervention where, at least in the past, there has not been any need for an intervention? DR MITCHELL: I think some of my comments were directed exactly at that possibility. As you travel around the world, in various locales, there is a great enthusiasm for these endografts. And clearly, unless somehow regulated, I think there would be a lot of use that would not be necessary. So we have tried to encourage, certainly in our own experience, use of grafts only for patients who truly exhibit surgical indications, both for dissections and aneurysms. I feel strongly that until we have more data, endograft use should be limited to those patients. DR MARIN: I cannot dispute that; I think that is correct, but I think the fear is greater than the actual event. I think the number of patients who have the kind of choice, small lesions that are amenable to this type of prosthesis is very limited. The patient with a small penetrating ulcer that may be ideal, or the relatively small fusiform aneurysm that has a good neck proximally and distally, is just not that common in most practices. What is common are patients with disease that extends to the visceral segment or more proximally to the arch, and in that setting, maybe some combined procedure does make sense, but not in patients with aneurysms smaller than would represent surgical indications. I think we are pretty comfortable with that approach, and that is what drives usage in most centers of excellence. DR KOUCHOUKOS: Dr Buffolo, can you comment on the high prevalence of aortic dissections in your series? DR BUFFOLO: First of all, for the abdominal aneurysms, I think that the results are worse than for thoracic. This is our experience. The endoleak is more common in
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aneurysms of the abdominal aorta. And I still think that the five-star treatment of the AAA is conventional surgical correction. We use the endovascular approach for patients with comorbidities, very important comorbidities. That is our position regarding the abdominal aorta. So this is not the situation you are concerned about But for type B dissection, we have a different opinion. We started our experience with a complicated case, and now at this moment we treat acute cases even without complications. Why? Because in following up these patients in outpatient care you will see acquired pathology. There is a reentry tear usually at the level of the left renal artery, or the left iliac artery. So you develop a condition in which a stent in the patient is no longer possible. So in these kinds of patients, in a few years, you will have to do a thoracoabdominal approach. So, at this moment, if you see acute cases of type B dissection, the pathology is only a tear just distal to the left subclavian artery, and this is a very simple condition to treat with a stent. The best results we have are in type B acute dissections and penetrating ulcers. I presented the overall mortality 5 years ago, and it was 10%. But if I could present the mortality in the uncomplicated cases (I thought it was not fair to present those numbers), it would be better. But if you consider the mortality in the most recent 2 years, it is almost 0%. With this in view, in type B dissection, we prefer to treat these patients in the acute phase. With this approach you do not have acquired pathology. DR MARIN: I think there are distinctions between the types of practices people have and the patients they are seeing, because we just do not see patients like that. I see about two to three type B dissections, both acute and chronic, a week, and I cannot remember the last time I saw one where there was just an isolated tear in one segment just distal to the subclavian, and that was the only entry point. The ones that are referred to our group tend to have multiple entry and exit points. And when we have attempted to stent the chronic ones, they have had the highest failure rate in our hands. We can seal the upper tear or seal several of the dissection planes, but they always reenter somewhere below and then somehow find a way to communicate with the original channel. We just do not see those that have that single tear right at the left subclavian, which I agree would be ideal candidates for stent grafting. DR KOUCHOUKOS: In the few minutes remaining, let me just address one other issue: the branch grafts. We have seen some very interesting videos and angiograms this afternoon about the use of these grafts, and also we saw some information from the presentations that the embolic rate is not inconsequential. How are we going to deal with this problem in the future? To me, placing these endovascular grafts into potentially severely atherosclerotic subclavian, carotid, renal, and visceral vessels makes chills run up and down my spine. Maybe I am just overreacting, but I really have concern about this. Clearly, this problem has to be resolved. How are we going to resolve it? We saw some filters used, but that certainly would add to the complexity of the procedures.
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So let me ask Dr Hosokawa and Dr Usui to comment on that, because they made these presentations. DR KAZUI: Every surgeon knows what the aortic arch looks like when you do open surgery. There is a lot of atheroma around the orifices of the arch vessels. So I am afraid if you put a catheter through the arch vessels in doing the stent graft, this may cause a high incidence of stroke. I would hate to do this kind of a procedure, particularly in the case of an atherosclerotic arch aneurysm. I probably feel the same way about thoracoabdominal aortic aneurysms, too. DR HIROAKI HOSOKAWA (Toyohashi, Japan): In our experience, the three-branched stent graft has a high incidence of brain thrombosis, and now we are developing a detachable filter device to prevent distal embolism. And it seems to be working, but it is time-consuming and sometimes it is difficult to retrieve through the stent graft. We need more experience using this kind of device. DR MARIN: I spent the past 6 years trying to develop a commercially available branch endograft, and I am quite confident that at Aortic Symposium IX, in the United States, we will not have a branch graft for the arch or the visceral segment. The number of patients who will fit the strict anatomic criteria is so small that there is not an industry in America that would be willing to take on the clinical trials and the complexity to develop the technology. DR SAFI: I second your fear from these branch grafts, Dr Kouchoukos. And we always, as my friend, Scott Mitchell, said, have to be diligent in our follow-up of these patients. In the recent study by the VA of the natural history of infrarenal abdominal aortic aneurysms 5 cm and less, the incidence of rupture is 1% per patient per year. Whereas in a modular graft in the infrarenal position, the incidence of rupture in the treated group was 1.5 patients per year. So we have to be careful about all these things. If I have an infrarenal abdominal aortic aneurysm, do I want to have a CAT scan every 3 months? Rather, I will go to a good surgeon who can do it with less than a 2% mortality rate, and with Viagra available, you do not need to worry about the pelvic nerves. DR MICHAEL JACOBS (Maastricht, The Netherlands): One of the advantages of a collective data bank, as we have in Europe (like EuroSCORE), is that it keeps us awake and alert. Like everybody else, we do 15 or 20 thoracic aortic aneurysms by means of endografting, but these collective data banks really show us the figures. And I can tell you that the data we have in Europe show a considerably higher incidence of paraplegia, renal failure, and mortality than we heard today. One of the complications I did not hear about this afternoon is what we observed during the last 3 months in our own hospital. We inserted a perfectly positioned endograft for an acute type B dissection; the indications for treatment were ischemic problems, renal insufficiency, a dead leg, and even rupture. Despite the perfect position, in 3 patients during the last month, this type B dissection (in 1 patient within 2 days, another within a week, and a third within 4 weeks) retrogradely involved
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the aortic arch and turned a type B dissection into an acute type A dissection, requiring acute arch replacement. I wonder whether the panel surgeons have also experienced this dramatic complication. Because I can tell you it is no fun in the middle of the night to open up an aortic arch, and deep in the proximal descending you see that fixed graft, which you cannot get out unless you use a metal scissors. You feel very strange during that procedure to have to tear that thing out and then replace the arch. Have you ever experienced that? DR SAFI: I had experience with one we were following with a type B dissection treated medically. He saw his friend, a gastroenterologist, who gave him Maalox and sent him home. And a week later he came and did an arteriogram (he is an interventional radiologist), and at noontime he was found dead. Luckily somehow we revived him. The antegrade dissection does happen, even spontaneously, but the problem of removing unsuccessful endografts is an important issue. In the last 5 years I have removed at least 20 grafts inserted either in the infrarenal or in the descending thoracic aorta. It is a mess if you do not open the aorta and remove them. In the infrarenal abdominal aorta, you cannot do it with the anchoring devices located above the renal arteries, short of a thoracoabdominal incision, because if you try to pull the graft out, you will rip everything off. We have a cardiologist now in our institution, who, when I first went there about 2 and a half years ago, had a coil for infrarenal abdominal aortic aneurysm. And he wanted me to be a coinvestigator. I told him this was tried in the 1930s, and they even put in some kind of wire and with electricity clotted it. Why does he have to repeat that? And he has 20 cases! I have operated on 10 of them in more than 3 years. All of those cases were billed as inoperable and then 2 or 3 years later they became operable. DR MARIN: We published our series of 9 patients who had infrarenal aneurysms with proximal thoracic dissections. The proximal dissections were small, and these were sick patients. Of the 9, we had 1 patient in whom we placed a stent graft sealing the distal exit point of the infrarenal aneurysm, which resulted in a more broad dissection retrograde and enlargement of the thoracic dissection such that he required thoracic reconstruction and succumbed to that. So the placement of stents in the dissected plane can result in retrograde dissection and can result in enlargement. A potential small tear that may have been there may enlarge significantly once the outflow tract or the distal dissection is sealed. DR BUFFOLO: I would like to ask a question of Dr Jacobs. What kind of stent do you use: auto-expandable or balloon-expandable? DR JACOBS: This was just a regular Talent stent that we positioned over the left subclavian covering the tear. DR BUFFOLO: But is it balloon-expandable or auto-expandable? DR JACOBS: Auto-expandable. DR BUFFOLO: Because this happens with balloonexpandable stents.
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DR JACOBS: Yes, sure. DR JEAN-PIERRE NORMAND (Quebec, Canada): I have two questions. First, in a patient with a very short neck between the left subclavian artery and the aneurysm, what do you suggest: a preop bypass, a stent with one branch, or a late bypass if the patient has symptoms? And a second question. Do you assess the vertebral arteries before stent grafting? DR MARIN: We do a transposition or a bypass. The procedure is benign enough and simple enough that if a patient is too sick to undergo a carotid-subclavian transposition, you have to really question whether or not fixing their aneurysm is worthwhile in terms of longevity. Whether the transposition has to be done or not is a question, because there are many people publishing series where they do not do it and they just cover the subclavian routinely without difficulty. I suppose that could be done, but it is simple enough to do the transposition. Transposition maintains perfusion to the vertebral, which may in some fashion, along with the other collaterals from the subclavian, contribute to spinal cord circulation, and we routinely will do the transposition. And if the neck is short, as you asked in the first question,
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we always do it. Because even if you could sneak a stent graft in with a relatively short neck, you can end up with a good cosmetic result at the completion of the procedure and then give Dr Safi plenty of work to do later and complain about, because the patient will come back in 6 months with a failure. DR BUFFOLO: We had 14 cases of intentional occlusion of the left subclavian artery, and in only one case was it necessary in the late follow-up to create a shunt. Nothing happens. But the problem is not this. The problem is the danger of occluding the left carotid artery that in some cases is very close to the left subclavian artery. For these situations, we prefer to do endoscopy with a special program called the Navigator; you do a real aortoscopy noninvasively. If there is some doubt that occlusion of the left subclavian artery by the stent can compromise the origin of the left carotid, this is not a suitable indication for a stent. This is an indication for an open approach through the aortic arch. DR KOUCHOUKOS: Thank you. Our time is up. I want to thank the panelists and the audience for their participation.