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J Thorac Cardiovasc Surg 2003;126:1663-1664
© 2003 The American Association for Thoracic Surgery

Letters to the editor

Authors should list confounding factors and alternative explanations for adverse events seen with new technologies

^a Cardiac Surgical Unit, Harefield Hospital, Middlesex, United Kingdom

To the Editor:

Two articles in your February 2003 issue raise concerns about the Symmetry connector (St Jude Medical, St Paul, Minn) for coronary artery bypass surgery. Hornik and colleagues¹ reported 4 of 70 uses and Reuthebuch and colleagues² reported 7 of 77 uses of Symmetry where severe proximal stenosis occurred. Implicit in both articles is a suggestion that the Symmetry device contributed to proximal graft failures. The observations of Hornik and Reuthebuch, however, cannot be regarded as evidence of such an association for 2 main reasons (neither of which were highlighted in the articles).

1. The practice reported is not typical of that in most cardiac units. For example, in Hornik's group only 18 of 45 patients received internal thoracic artery (ITA) grafts. Also unusual was that none of the 4 patients whose history was detailed received an ITA even though 3 were below 60 years of age and 2 had severely calcified aortas, factors most surgeons would regard as indications for ITA grafting. Also, the 29% conversion rate for their off-pump coronary artery bypass patients is substantially higher than seen in most units. Both reports listed aortic calcification as a principal indication for use of the device. It would not be unreasonable to expect more proximal graft failures in patients with aortic calcification regardless of anastomotic technique. Differences in practice or technique therefore could be an alternative explanation for the proximal failures.
   
2. The authors have not made any comparisons to patients having surgery using conventional techniques. Proximal graft failure is by no means unique to Symmetry and is well documented using standard techniques.³ Without systematic angiography of all patients, particularly those with aortic calcification, reliable comparisons with standard techniques cannot be made.
   

As presented, neither report is sufficient to caution against use of the device. Also not considered is the benefit of the technique as it is plausible that morbidity due to aortic calcification or aortic clamping (and by extension the net morbidity and mortality) was reduced by use of the device. Adverse events must be weighed against such benefit, as in at least some cases the benefit of a new technology will outweigh any adverse events. What is required are comparisons between grafts done with Symmetry and those done with standard techniques (preferably with the proximal anastomosis constructed first). Only then can any incremental risk (or benefit) be identified and quantified.

I have never used the Symmetry device and have no special interest in the device or technique; indeed, there may truly be an association between the Symmetry and proximal graft failure. My concern is in the wider area of dissemination and adoption of new technologies. Without statements on data limitations, publication of biased noncomparative data on any new technology is potentially alarmist (or overoptimistic), may prevent proper evaluation and development, and may unnecessarily hinder (or accelerate) uptake of new technologies, some of which could be potentially beneficial (or harmful). Authors of reports on new technologies should list limitations and highlight any confounding factors or alternative explanations for adverse events (or benefits); otherwise readers could be inadvertently misinformed.

References

1. Hornik L, Tenderich G, Minami K, et al. First experience with the St Jude Medical, Inc, Symmetry Bypass System (Aortic Connector System). J Thorac Cardiovasc Surg. 2003;125:414–417[Free Full Text]
   
2. Reuthebuch O, Lachat M, Kadner A, Turina M. Early bypass occlusion in patients with the St Jude Medical Symmetry connector. J Thorac Cardiovasc Surg. 2003;125:443–444[Free Full Text]
   
3. FitzGibbon GM, Burton JR, Leach AJ. Coronary bypass graft fate: angiographic grading of 1400 consecutive grafts early after operation and of 1132 after one year. Circulation. 1978;57:1070–1074[Abstract/Free Full Text]
   

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Ani C. Anyanwu Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Anyanwu, A. C. Search for Related Content PubMed PubMed Citation Articles by Anyanwu, A. C. Related Collections Coronary disease Related Article