Division of Epidemiology and Community Health, University of Minnesota, Minneapolis, MN
Division of Cardiology, Jewish General Hospital/McGill University, Montreal, Quebec, Canada
Divisions of Cardiology and Clinical Epidemiology, Jewish General Hospital/McGill University, Montreal, Quebec, Canada
Article Outline
Dear Editor:
We thank Dr Navarese et al for their interest in our meta-analysis entitled “Effectiveness and safety of drug-eluting stents in vein grafts: A meta-analysis”1 and for the opportunity to clarify some of the methodological issues raised in their letter.
1.Recent observational studies: Dr Navarese et al identified 3 observational studies that were not included in our meta-analysis.2, 3, 4 These studies were published after our manuscript was submitted for publication. Their inclusion may have altered the estimates obtained from our analysis of observational studies but would not have changed our main conclusion—high-quality evidence from randomized controlled trials is required to conclusively address the use of drug-eluting stents in vein grafts.
2.Definition of MACE: We agree that there exists some heterogeneity in the definition of MACE across studies. We therefore used random effects meta-analysis models to allow for both within- and between-study heterogeneity when pooling data across studies. MACE was included as an end point despite its heterogeneity, as we felt that it was clinically important and would be of interest to the reader. To minimize this potential limitation, we also estimated the effect of drug-eluting stents on each component of MACE; and results were generally consistent across end points. These results are provided in Table III of our article.
3.Quality assessment: An assessment of study quality may have been useful to help characterize included studies and for sensitivity analyses. However, we do not believe that study quality should be used to determine which studies are included. Ultimately, the greatest threat to the internal validity of the included observational studies is confounding by indication, which is present in most observational studies and not thoroughly assessed by quality assessment scales such as the “Newcastle-Ottawa Scale.” This limitation of observational studies highlights the need for large, multicenter randomized trials assessing this issue.
4.Publication bias: We agree that funnel plots can be used to provide some evidence of the presence of publication bias. However, virtually all systematic reviews and meta-analyses are affected by publication bias to some degree; and although funnel plots can provide some reassurance, the possibility of bias remains. For this reason, rather than constructing funnel plots, we acknowledged that our results may be affected by publication bias in the limitations section of our article.
5.Heterogeneity: No formal assessment of heterogeneity was performed. The greatest source of heterogeneity was felt to be study design (ie, observational vs interventional) due to the inherent limitations of observational studies. Consequently, all analyses were stratified by study design.
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References
- Joyal D, Filion KB, Eisenberg MJ. Effectiveness and safety of drug-eluting stents in vein grafts: a meta-analysis. Am Heart J. 2010; 159:159-169.e4.
- Brodie BR, Wilson H, Stuckey T, et al. Outcomes with drug-eluting versus bare-metal stents in saphenous vein graft intervention results from the STENT (Strategic Transcatheter Evaluation of New Therapies) group. JACC Cardiovasc Interv. 2009;2:1105–1112
- Goswami NJ, Gaffigan M, Berrio G, et al. Long-term outcomes of drug-eluting stents versus bare-metal stents in saphenous vein graft disease: results from the Prairie "Real World" Stent Registry. Catheter Cardiovasc Interv. 2010;75:93–100
- Shishehbor MH, Hawi R, Singh IM, et al. Drug-eluting versus bare-metal stents for treating saphenous vein grafts. Am Heart J. 2009;158:637–643
PII: S0002-8703(10)00434-5
doi:10.1016/j.ahj.2010.05.028
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