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Ann Thorac Surg 1998;65:1551-1552
© 1998 The Society of Thoracic Surgeons
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Discussion |
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 Top Discussion |
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Beginning about 6 years ago we started replacing degenerated bioprosthetic mitral valves by completely excising the leaflets that are degenerated, leaving the stent intact, and attaching a reversed aortic St. Jude valve to the inflow aspect of the stent. By sewing a mechanical valve, in our case a reversed aortic St. Jude valve, cuff-to-cuff to the stent, which is left in situ, one can achieve a rapid and very effective replacement using the same size valve. Rather than a valve inside the stent, this is a valve-on-valve. About 2
years ago we extended this concept to the aortic degenerated bioprosthetic valve, whereby we would completely excise the degenerated tissue, excise the struts, remove them, and then suture to the outflow aspect of the stent of this valve a new mechanical valve, in our case a CarboMedics valve, thus achieving a valve-on-valve seating. This gives us a very effective, hemodynamically excellent result, and, again, in a very expedient way and avoiding any of the complications of explantation of these valves. We have so far operated on 35 patients with this approach, 26 for mitral and 9 for aortic bioprosthetic valve replacement, with no operative mortality and only one late death caused by cancer.
Doctor Akins, I have a short question for you. What is your preference when you replace these degenerated valves? I think your abstract alludes to a predominance of mechanical valves. Do you still feel the same?
DR AKINS: We are aware of Dr Geha’s innovative surgical approach, but we have not had the opportunity to use that yet.
In terms of which valve we choose, it has a lot to do with what we think the projected life expectancy of the patient is. We will use a bioprosthesis as patients get older. As can be seen in our Figure 2, there is an increasing incidence of bioprosthetic use in elderly patients, but certainly in this series about 70% of the valves that replaced the bioprostheses were mechanical valves.
DR HUGH E. SCULLY (Toronto, Ontario, Canada): I enjoyed your paper, Dr Akins, and I think you raise a very important question, which is the choice of the prostheses when one is doing multiple valve replacements in the younger patient.
Let me pose a specific question to you. What do you do with a 60-year-old woman whose mitral bioprosthesis has failed but whose aortic bioprosthesis, which has been in for 10 years, is still functioning? Do you do anything about the aortic valve under those circumstances, recognizing that in all likelihood that also will fail in time?
DR AKINS: Generally our approach recently has been to be more aggressive, and that is to replace both prostheses at the same time unless there is going to be a prolonged operation. Although there is variability in our group, I have become more aggressive about replacing bioprosthetic valves that have been in more than 8 to 10 years even though there is limited evidence of disease in them.
DR FRANCIS D. FERDINAND (London, England): Just to revisit the question of the type of prosthesis for the reoperation, were most of these patients referred from outside, and what had changed where your initial strategy was to place a bioprosthetic valve and then at reoperation change it to a mechanical valve? Second, could you just briefly describe the endocarditis cases preoperatively? Which type valves did they have, and what was your choice for replacement in the setting of endocarditis? Third, will the incidence of atrial fibrillation influence what you will use for a replacement device?
DR AKINS: Let me begin with whether we have a difference in the types of valves that were initially implanted. We, like most cardiac surgeons, became disappointed in the early 1970s with some of the problems with mechanical valves and jumped on the bioprosthetic bandwagon. We began to pay the price for that in the late 1970s and early 1980s, and that is when we began to see more bioprosthetic failure. If you will notice, the number of operations per year has actually fallen off a bit recently. Obviously, not all of the patients were operated on in our own institution.
For endocarditis patients, in terms of what valves we used to replace a failing prosthesis, it depends on the patient’s age. We do not believe that necessarily inserting a bioprosthesis or a mechanical valve has any particular advantage in the presence of endocarditis other than when the aortic root is destroyed. The German series has superb results with using all mechanical valves in the treatment of acute endocarditis, and we do not fear putting in a mechanical valve in a patient with acute endocarditis. In 1 or 2 of the patients in this series a homograft was used in the aortic root when the bioprosthesis failed. We do believe that there is some evidence out of New Zealand and Australia that supports the use of homografts as aortic root replacements for extensive endocarditis involving destruction of the aortic root.
DR FERDINAND: And then, finally, about the atrial fibrillation: will the incidence of atrial fibrillation influence what you will use for a replacement device?
DR AKINS: I do believe that probably does not influence us as much in terms of which valve we choose as does the intensity of anticoagulation that we may follow. Some people suggest that if the patient is going to be receiving warfarin anyway, why not just put in a mechanical valve? I happen to believe that there are some people who will still do better in the older age group with a bioprosthesis even in the mitral position. We know that many of these patients may eventually undergo other general surgical procedures, and it is a lot easier to stop the administration of warfarin for a day or two in those patients if there is a bioprosthesis in place than if they have a mechanical valve in place.
DR HARTZELL V. SCHAFF (Rochester, MN): There are a few notions in cardiac surgery that get carried forth from generation to generation, and one of them is that failure of a bioprosthesis is gradual, but your experience is similar to ours in that in many patients late failure of a bioprosthesis may be precipitous. What would your approach be to a patient who has a new murmur or new onset of moderate central regurgitation in a bioprosthesis that has been in place for 10 years?
DR AKINS: First we would have closer medical follow-up of that patient. In the past we would tend to treat that patient as we do somebody with native aortic regurgitation. If there is evidence of left ventricular enlargement, evidence of left ventricular failure, or a decrease in ejection fraction with exercise, we treat that patient with an aortic valve replacement, some might say somewhat more prematurely than if it were acute regurgitation.
DR SCHAFF: We generally operate early in such patients because the progression of regurgitation is not the same as in native aortic valve regurgitation.
DR AKINS: I agree with you. We are heading in that direction. The situation that you pointed out is something that needs more careful study.
DR JOHN D. OSWALT (Austin, TX): Do you have the total privilege of choosing which prosthesis you replace at the time of reoperation, or do your cardiologists get involved in this decision? We find it a little bit difficult sometimes to convince our cardiologists that the patients would do fine with a repeat bioprosthesis even if they are in atrial fibrillation and 81 or 82 years of age. Would you please comment?
DR AKINS: We allow them to recommend as much as they wish, but we decide.
DR W. R. ERIC JAMIESON (Vancouver, BC, Canada): What has been your reoperative mortality in the last 5 years for aortic valve replacement? Are there circumstances in which you may recommend two aortic bioprostheses in their lifetime? Has your reoperative mortality decreased to support such a recommendation?
DR AKINS: Exactly, we did not. Our mortality is actually slowly increasing in the last few years, but the operations have become more complex, there are more concurrent operations being done, and the patients now are a mean of 10 years older than in the earlier part of the study, so that confounds the issue. For an isolated aortic valve replacement, I have no fear about putting in a second bioprosthesis. Getting out to third and fourth bioprostheses, then I begin to have an issue. There was a slight increase in our operative mortality between first, second, third, and fourth reoperations, but our series was not large enough to demonstrate a statistically significant difference.
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