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Ann Thorac Surg 2000;70:790-791
© 2000 The Society of Thoracic Surgeons
Discussion
DR LAWRENCE H. COHEN (Boston, MA): It is a very provocative subject you have brought us today. To your credit, you engaged one of the Olympians of statistical treatment of valve data, Dr Grunkemeier, to independently review your data and you did not exclude the "sicker" patients in your study. If I understood it, the main point in this nonrandomized, nonprospective, non-same surgeon study is that if you put in a stentless valve, your patients will live longer than if you put in a first-generation porcine valve, which is the valve that was compared with the stentless valve. Perhaps there is an implication here that this may aid you in survival versus all stented biological valves.
Although I enjoyed your presentation very much and I am impressed with the elegance of your statistics, I have had the chance to review your manuscript, which was beautifully done as well, and the data of other comparative series, and I have to disagree with the conclusion based on what you presented us today.
As you know, long-term survival after valve operations is an exceedingly complex analysis. You have nicely compared the preoperative demographics, including the presence of coronary disease and reoperations. In your paper, however, and we are now talking about the era of 1993 to 1997, as you pointed out, the operative mortality in both groups was higher than I would have expected: 8% in your personal series of the stentless valve and 12% in a group of stented porcine valves. I would make the point and I would like you to comment on this, that there is a potential serious myocardial protection problem for yours and the comparative series. I notice that you use St. Thomas’s clear cardioplegia, which may adversely affect long-term survival from injury to the heart during the operative period as represented by this high operative mortality.
In the same time period, 1993 to 1997, I reviewed my personal series at the Brigham, and during that time we performed 325 aortic valve replacements with similar demographics, including a 42% incidence of concomitant coronary disease and a 15% incidence of reoperation with an operative mortality of 2.8%. Now, using life table analysis on that group, we have a similar survival of about 85% to your Freestyle group. So I wonder if you would comment on that particular point.
You mention that there was an incidence of coronary disease, and, as we know, the extensiveness of revascularization may alter survival as well, and perhaps you might want to give us the incidence of complete revascularization. You did mention your follow-up included serial postoperative echoes, perhaps you could show us that the LV function on those patients is about the same as pre-op values, suggesting that possibly intraoperative factors may have influenced postoperative survival by its influence on left ventricular function.
A number of second generation stented biologic valves, including the pericardial valve studies by Aupart from France and Pelletier from Canada, and porcine valve studies by David, showed that, including operative mortality, the long-term survival at 5 years in those studies was 85%, mid 80s similar to what you have shown for the stentless valve.
So, I think that you have brought us a very provocative study and one that is going to require a lot more study of these factors in years to come. You may be right, but I personally think that these data, complicated by factors I have mentioned, do not support your thesis.
Another couple of questions I might ask you is, you mentioned the LV regression, which I think is a potentially great advantage of these valves. Can you comment on what has happened in these particular patient groups in that regard, both stented and unstented in that group? Finally, the technical problems of the dehiscence of the suture lines, yours seems very low. Any late factors, any late incidence of that that you would like to bring to our attention?
Thank you very much for bringing this provocative study to our attention.
DR MICHAEL J. REARDON (Houston, TX): Doctor Westaby, I congratulate you on a very nice study. I do have some questions for you. It would seem intuitive that as the annular size gets smaller, choosing a valve of good hemodynamics becomes more and more important, and if survival is based on improved hemodynamics, it might seem that as you move to the smaller annulus, the survival difference might widen. Knowing that a manufacturer’s valve size is a very poor surrogate for annular size, in your study, could you and did you compare different annular sizes and the survival difference between the valves to let us know if the survival difference either stayed the same or dissipated as you moved towards larger annular sizes?
DR REX STANBRIDGE (London, UK): I would like to congratulate you, Dr Westaby, on your excellent presentation. I would like to ask you, in the Carpentier-Edwards group, what proportion of operations was carried out by surgeons in training, and do you think that there may be differences in myocardial protection in this group, including cross-clamp times, which may have a long-term effect on the outcomes?
As Dr Westaby did not hear the question, perhaps he would wish to reply now.
DR WESTABY: The question about intraoperative myocardial protection is a very interesting one. Whether that can influence long-term outcome in hospital survivors is an important question. Both groups of patients had identical myocardial protection with cold antegrade cardioplegia (St. Thomas’s solution). So I think both groups would have had the same problem.
I made it clear about the hospital mortalities because I think it is important to show that there was no significant difference between the two groups, which would have influenced the actuarial survival curves. The extent of coronary disease was the same in both groups, it was about 40%, and as near as possible, we performed complete myocardial revascularization in the patients, however elderly they were.
We have studied left ventricular mass regression in great detail in the Freestyle valve patients and, to some degree, in the Carpentier-Edwards patients. What we find is that left ventricular mass regression goes down virtually to normal limits within 6 months of receiving a stentless valve, whereas with a stented bioprosthesis it rarely reaches normal limits and it falls off at a slower rate. We believe that this affects the long-term outcome, because the Framingham study showed that left ventricular mass was an independent risk factor for cardiac death.
In terms of the annulus sizes and what type of valve you can get into an individual patient, I will say that as well as having much better flow characteristics, it is always possible to implant a larger size stentless valve into an individual annulus. I implant the stentless valve on top of the native annulus, and whereas I do not size the sinotubular junction as Dr David does, I size the annulus, but then choose a valve that is one size larger. One can always use a prosthesis with a larger orifice area when implanting a stentless valve.
We have looked in great detail and published about the influence of effective orifice area index. The critical feature is that virtually every patient with a stentless bioprosthesis has an effective orifice area index greater than the watershed of 0.8 cm2/m2. So very few patients have patient-prosthesis mismatch.
So in conclusion, Mr Chairman, thank you very much for allowing me to present this paper and I appreciate your attention. Thank you.
Related Article
Ann. Thorac. Surg. 2000 70: 785-791.
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