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Ann Thorac Surg 1998;66:2153-2154
© 1998 The Society of Thoracic Surgeons
a Department of Cariothoracic Surgery, Albert Einstein College of Medicine, Bronx, New York, USA
As originally published in 1992:
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The article was a report on the trial conducted by Baxter Edwards to satisfy the regulatory requirements for free clinical use in the United States. Work done in ten institutions was pooled, with the bulk of the cases coming from four programs. The valves were available for implantation from August 1981 to July 1985, and reported finally at The Society of Thoracic Surgeons meeting in February 1991. The minimal follow-up at the time the report was given was 6 years. As a result of this, we were able to come to reasonably firm conclusions about the value of the device. The valve was finally released for general distribution in October 1991.
The Montefiore Medical Center participation in the trial was directly related to our research interest in heart valves and our previous clinical experience with pericardial valves. We had originally chosen to use the Ionescu-Shiley pericardial valve because, on testing with our pulse duplicator, it had superior hemodynamic performance, compared with porcine bioprostheses. This was made possible by the fact that the valve could be fabricated rather than being harvested and suspended within a frame. We and others confirmed this superior hemodynamic performance in clinical studies but were soon confronted with early structural failure, especially in the mitral position. This in turn forced us back to the laboratory, where, after setting up an accelerated wear testing system, we were quickly able to define the problem as one of abrasion wear [1].
With this background we did not respond immediately to manufacturers’ offers of new and improved pericardial valves for trial. We took these, the Hancock, the Ionescu-Shiley II, the Mitroflow, the Edwards, and a porcine control valve to the laboratory. The best hemodynamically was the Hancock; it was also the worst in the wear tester. The best in the wear tester was the Edwards and for this reason, together with its good hemodynamics and what appeared to us to be a user-friendly design, we chose to participate in the trial [2]. It is interesting to note that, at our rate of 1600 cycles/minute, the number of accelerated cycles to structural failure was considerably less than 100 million for all the devices tested. This is far less than the 200 million that is now required in the regulatory guidance documents. Nevertheless, the test discriminated most effectively between these devices. The Ionescu II and the Hancock, tried by others, failed within a year, the Mitroflow was adequate and has not done badly, and the Edwards has by now proved itself in the aortic position in numerous series of patients, with good results coming from France, Germany, Canada, and the United States.
A cohort of patients from the series reported in 1992 was chosen at random for long-term follow-up. These patients have continued to be followed up annually since 1991 and a recent publication describes the results at 14 years [3]. The actuarial freedom from explantation for structural failure in the aortic position was 76% for valves implanted in patients less than 65 years old and 96% for those implanted in patients older than 65 years of age. The failure mode was almost always calcification; tearing in the absence of calcification was extremely rare. Inevitably there was the disappointment, common to all series of patients undergoing valve replacement, that freedom from death due to all causes was low, at 39%. Some of the deaths were sudden or unknown, and by convention these are ascribed to the valve. Although some of these are undoubtedly not caused by valve failure or from a valve-related cause, some may be because of persistent left ventricular hypertrophy. Excellent clinical results have been reported in a series of patients (mean age, 72 years) who received size 19 Edwards pericardial valves and were followed-up for an average of 4.45 years [4]. However, the average peak gradient, at 30.5 mm Hg, was higher than is found with stentless aortic valves, and may or may not provide the same level of regression of left ventricular hypertrophy that occurs with the latter. Further careful comparative studies will be needed to prove that late sudden death will be as low with a 19-mm Edwards pericardial as with a stentless aortic valve that will fit the same size annulus. We continue to enlarge the aortic root even for the sake of inserting a size 21 pericardial valve.
The discussion so far has been about aortic valves. In 1981, although we thought that the Edwards pericardial valve had an excellent design, we were nervous about exposing it to the unquestionably more severe test of the mitral position. Reports from centers outside the United States now indicate that these fears were unfounded; valves in aortic and mitral positions appear to have similar structural failure rates and the same calcific mode of failure [5].
The Edwards pericardial valve has demonstrated clearly that with good design, pericardium will perform excellently as a heart valve substitute. To achieve maximal benefit for younger patients, it will be important to add an effective anticalcification treatment.
References
This article has been cited by other articles:
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  J. J. Pereira, M. S. Lauer, M. Bashir, I. Afridi, E. H. Blackstone, W. J. Stewart, P. M. McCarthy, J. D. Thomas, and C. R. Asher Survival after aortic valve replacement forsevere aortic stenosis with low transvalvular gradients and severe left ventricular dysfunction J. Am. Coll. Cardiol., April 17, 2002; 39(8): 1356 - 1363. [Abstract] [Full Text] [PDF]
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