LETTER TO THE EDITOR
Choice of prosthetic heart valves: 20-year results of the Edinburgh Heart Valve Trial
Peter Bloomfield, MD
Royal Infirmary of Edinburgh, 1 Lauriston Place, Edinburgh EH3 9YW, Scotland, United Kingdom
peter.bloomfield{at}luht.scot.nhs.uk
A recent edition of the Journal carried a robust debate between David S. Bach (1) and Shahbudin H. Rahimtoola (2) on the choice of prosthetic heart valves for individual patients requiring valve replacement surgery. Bach's (1) thesis was that prosthetic heart valves have evolved over the years to provide superior hemodynamics and durability compared to older valves, which had been included in randomized trials. Rahimtoola's (2) commentary, "The next generation of prosthetic heart valves needs a proven track record of patient outcomes at  15 to 20 years," emphasized the importance of obtaining long-term data not available for the newer prostheses, and he stressed how important long-term data are from prospective randomized trials.
Bach (1) notes that in the Edinburgh Heart Valve Trial there was a trend favoring improved survival in association with the mechanical Bjork-Shiley prosthesis. We have recently published data from the 20-year follow-up of patients randomized in this trial. Interestingly, the trend toward improved survival at 12 years diminished as patients were followed for 20 years. Bach (1) also noted, "However, freedom from all valve-related complications for tissue and mechanical prostheses was indistinguishable at 12 years." In fact, when we followed our patients for survival without a major event (i.e., freedom from death, re-operation, major hemorrhage, embolism, or endocarditis) there was a significantly better survival in favor of the Bjork-Shiley prosthesis for those undergoing mitral valve replacement (3). This benefit became apparent after 10 to 12 years of follow-up and as survival cures continued to separate thereafter.
This difference in survival without a major event was almost entirely accounted for by the increased need for re-operation in patients who had received a bioprosthesis with increasing years of follow-up. There was no significant difference in survival without a major event in the subgroup of patients who had undergone aortic valve replacement. These results would not support Bach's (1) statement, namely that "Bioprostheses were superior to mechanical valves prior to 12 years after surgery and were equivalent thereafter." The risk of anticoagulant hemorrhage is of course not limited to those patients receiving a mechanical valve. We noted an increase in the use of anticoagulants in patients who had been randomized to receive a bioprosthesis during the course of the trial. At five years, 15% of patients with a porcine aortic prosthesis and 36% of those with a porcine mitral prosthesis were receiving warfarin; by 15 years this proportion had risen to 33% and 57%, respectively. The increasing use of warfarin with the passage of time reflected concomitant conditions such as atrial fibrillation and chamber dilation favoring the use of long-term anticoagulation.
These results emphasize the need for prolonged follow-up of patients in randomized trials of prosthetic heart valves as it is only with such prolonged follow-up that important differences between prostheses are seen to emerge. It is perhaps ironic that data from the Edinburgh Trial and the U.S. Department of Veterans Affairs trial have provoked such debate within the editorial pages of the Journal of the American College of Cardiology. We had submitted the manuscript of the 20-year follow-up to the Journal more than a year prior to Bach's (1) viewpoint and Rahimtoola's (2) commentary and previous editorial. The Journal declined our manuscript; acceptance may have cast more light than heat on the subsequent debate.
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References
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1. Bach DS. Choice of prosthetic heart valves: update for the next generation. J Am Coll Cardiol. 2003;42:1717–1719[Abstract/Free Full Text]
2. Rahimtoola SH. The next generation of prosthetic heart valves needs a proven track record of patient outcomes at 15 to 20 years. J Am Coll Cardiol. 2003;42:1720–1721[Abstract/Free Full Text]
3. Oxenham H, Bloomfield P, Wheatley DJ, et al. Twenty-year comparison of a Bjork-Shiley mechanical heart valve with porcine bioprostheses. Heart. 2003;89:715–721[Abstract/Free Full Text]
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