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Ann Thorac Surg 2000;69:1331-1332
© 2000 The Society of Thoracic Surgeons
Discussion
DR ROSS M. UNGERLEIDER (Durham, NC): Well, Dr Knott-Craig, you have established a tradition of presenting outstanding work year after year at the Southern Thoracic, and this year is no exception, and I too rise with you to appreciate what we have learned from Dr Elkins in pioneering the use of human valve tissue in our patients.
Your data are interesting. If not statistically significant, they certainly seem to be suggestive that over the long term the autograft may be a durable aortic valve substitute, but I am curious about two things, if you do not mind responding to them.
First, it was pointed out by you, I think quite appropriately, that there was a difference in the patient populations, and especially with respect to the increased incidence of endocarditis and other patient morbidity factors in the homograft population, and I wonder if you could comment about how that might have affected the long-term outcome for the valves in those patients? In fact, if you could specifically talk to us about what you meant by valve degeneration, as it was clear that even with valve degeneration many of these patients were still existing with their homograft valves. Indeed, considering biases of patient selection, your data would suggest that an aortic homograft is an excellent choice for aortic valve replacement over the intermediate term.
The other question I have for you is more of a philosophical one. We see many patients with bicuspid aortic valve disease and dilated ascending aortas, and there is a concern that these patients have some form of collagen vascular disease. I would interpret the data that you show to suggest that a homograft might actually be a very good aortic valve replacement for these patients rather than an autograft, simply because the durability of the homograft appears to be quite good out to and beyond 10 years. I wonder whether you could talk about your philosophy regarding the use of autografts now that you know that homografts can also last quite well and for quite a long time when used as a root replacement.
This is an excellent review and I congratulate you on yet another fine paper.
DR KNOTT-CRAIG: In terms of valve degeneration or primary valve failure, the definition by Yacoub includes severe aortic regurgitation or a gradient exceeding 35 mm Hg across the homograft. That constitutes primary valve failure or valve degeneration.
In terms of the second very interesting question, I do not think the answers are available yet. I would suggest that just as the early pioneers including Ronald Elkins modified their techniques to overcome conditions that detract from the advantages of the autograft, the time is now ripe for the younger generation of surgeons to find ways, to do the operation better, so that this operation, which clearly seems to be the most appropriate operation in the younger patient population, can be done with even a better outcome. However, I submit that in a large proportion of patients, the homograft is as good as the autograft, at least during the follow-up period of up to 10 years.
DR JOHN D. OSWALT (Austin, TX): I too wish to congratulate you, Dr Knott-Craig, on such a fine paper and also want to acknowledge Ron Elkins for the support and foundations that he has laid for my work doing the Ross procedure. He has been totally invaluable.
I also rise to echo our 10-year results with the Ross to show that our data are very comparable and that the valve is sustainable at least for this length of time, and I have not prepared slides since last year as a discussant my friend, Ross Ungerleider, nailed me grandly for that. Our long-term survival at 10 years is 92%, with freedom from autograft explanation of 93% and freedom from right ventricular outflow tract replacement or the homograft replacement at 99%.
And so what this amounts to is 10 valve failures over this 10-year period of time, and what we have noticed is that with the change in the techniques all of those valve failures were in the first 5 years, none in the second 5 years. The Ross procedure was an operation, at least in my mind, in evolution up until about 4 or 4
years ago. We now have to go forward with these technique changes and see our results.
But I think that we are going to see in the follow-up that Chris could probably address as one of my questions is, do we not see that most of your autograft failures were in that first 5 years of the study as opposed to those during the past 5 years, and have you separated those statistics out to share with us? And also the fact that you may discuss a little bit about the technical changes that we have now undergone, particularly addressing the bicuspid valve with a dilated aortic root.
Thank you for the chance to discuss your paper.
DR KNOTT-CRAIG: I would like to skip to the last question because it is a topic in itself.
Briefly, the autograft was designed to solve a problem, the problem being the lack of a good alternative aortic valve. It has come a long way since then. Still remaining are problems like the bicuspid aortic valve, the patient with a dilated aortic root, and the patient with connective tissue abnormalities. The challenge is how to make the operation transcend those difficulties so it remains a good operation.
In terms of the valve degeneration, there have only been three patients that needed reoperations, and these were done within the first 5 years of their operation. There really have been very few reoperations on the autograft beyond that early hazard phase period.
Dr KEVIN D. ACCOLA (Orlando, FL): Just a quick question, Dr Knott-Craig. I also enjoyed your paper and your institution’s excellent data. Have you gone back and looked at the patients with the homografts that had degenerative changes over the 10-year period and seen if there was any difference in the patients that those homografts were harvested from initially with regard to age or status? You mentioned that your autografts were placed in younger individuals. It would be interesting to determine whether there were any differences in the harvested homograft groups.
DR KNOTT-CRAIG: I do not have data from our study to answer those questions. There are data becoming available both from Mark O’Brien’s study and also from Magdi Yacoub’s study that suggest that the younger donor in the adult age group has a better quality homograft. Second, it is very difficult to draw comparative analyses from our patient cohort, because although we designed a homogeneous population group, in effect the groups are very different. Patients with endocarditis have a lifestyle conducive to recurrent endocarditis, which leads to homograft regurgitation and explantation.
DR DAVID R. CLARKE (Denver, CO): I too would like to congratulate you, Dr Knott-Craig, on the excellent work and second your nomination of Ron Elkins as a pioneer in this field; as a matter of fact, he is probably "the" pioneer in the United States. I would like to ask you about reintervention in these two groups. It seems to me that although you mentioned that reintervention down the line was probably more common with the homograft than the autograft, I also think that the qualitative nature of that reintervention in terms of mortality, morbidity, and ease is very important, and possibly you could comment on the specific types of reintervention in the autograft group and their difficulty versus the types of reintervention in the homograft group and their difficulty along with mortality and morbidity.
DR KNOTT-CRAIG: Thank you very much. There have been three reoperations on the autograft in this time frame: in 2 patients the autograft could be repaired and in 1 patient it needed to be replaced with a homograft. One patient subsequently had the autograft replaced at a different institution at a third operation. In terms of the other reoperations, there have been five pulmonary homografts in the autograft population that have needed to be replaced over the follow-up period, and this is in contradistinction to five aortic homografts that have been replaced over follow-up period.
Related Article
Ann. Thorac. Surg. 2000 69: 1327-1331.
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