Exploring groups at high risk of restenosis

Adrian Bagust, Ameet Bakhai, Rumona Dickson, Yenal Dundar, Ruaraidh A Hill* and Tom Walley

Liverpool Reviews and Implementation Group [LRiG], University of Liverpool, Sherrington Buildings, Ashton Street, Liverpool L69 3GE, UK

* Corresponding author. Tel.: +44 151 79 45541; fax: + 44 151 79 45477 (E-mail: r.hill{at}liv.ac.uk).

We thank Scheen and colleagues for their interest in our systematic review1 of drug-eluting coronary artery stents (DES) and congratulate them on their success in obtaining largely unpublished data for diabetic and non-diabetic subgroups for six major trials of DES. We feel it would be useful for the sources of these data to be listed, and the method of interpretation of restenosis rates should be described. Our own analysis of patient subgroups,2 including diabetes, was conducted for the National Institute for Clinical Excellence early in 2003,3 but was limited by the data available to us. It is for this reason we did not include these subgroup analyses in our recent publication.1 We have since utilised further data available from trials and our regional cardiothoracic centre to explore patient subgroups in some detail.

Although Scheen and colleagues provide an interesting analysis, their correspondence does not consider important related, but distinct issues. Our observations on three such topics are as follows:

(1) As Scheen and colleagues' analysis shows, and supported by our own more limited subgroup analysis, there is no convincing evidence that DES act differently in reducing restenosis in patients with diabetes in relative terms. It seems that DES benefit all patients with a likely poor outcome to the same degree — absolute differences arise from the underlying propensity to restenose.

(2) In aggregate terms, patients with diabetes are more likely to suffer MACE or revascularization than those without. However, in SIRIUS4 these patients were more likely to have hypertension, triple vessel disease or impaired left ventricular function. It is not clear that after correction for these and other risk factors, as well as anatomical variables, case-mix-adjusted patients with diabetes are at more or less risk of restenosis than non-diabetics. In other words, diabetes may be associated with greater risks, but this is not necessarily causal.

(3) Our patient level analysis of both trial2 and audit data suggests that diabetes per se is not an independent risk factor for revascularization, but may be merely a convenient aggregate marker for other causal factors. It is important to distinguish between those variables which reflect the long-term risk of incident or progressive arterial disease (of which diabetes is clearly a primary member), and those variables which relate to the short-term risk of restenosis in individual lesions. The former are essentially systemic, whereas the latter are more likely to be localised and related to anatomy. Our forthcoming economic analysis includes results suggesting that the latter may be the more important.

In conclusion, our own research would suggest that small vessels and anatomical complexity are more influential in predicting restenosis than simply diabetes. These findings could be confirmed by analyses of individual patient data from the existing and ongoing trials of DES. This would remove the need for further specific but expensive studies of DES in diabetics, as called for by Scheen and colleagues.

References

  1. Hill R, Dundar Y, Bakhai A, et al. Drug-eluting stents: an early systematic review to inform policy Eur Heart J 2004;25:902-919.[Abstract/Free Full Text]
  2. Hill R, Bagust A, Bakhai A, Dickson R, et al. Coronary artery stents: a systematic review and economic evaluation Health Technol Assess 2004;8:1-256.
  3. Hill R, Bagust A, Bakhai A, et al. Assessment report: coronary artery stents rapid systematic review and economic evaluation — Addendum B, 2003. Available from: URL:http://www.nice.org.uk/pdf/Stents_addendumB. pdf.
  4. Moussa I, Leon MB, Baim DS, et al. Impact of Sirolimus-Eluting Stents on Outcome in Diabetic Patients: A SIRIUS (SIRolImUS-coated Bx Velocity balloon-expandable stent in the treatment of patients with de novo coronary artery lesions) Substudy Circulation 2004;109:2273-2278.[Abstract/Free Full Text]




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