Letter by Testa et al Regarding Article, “Pathological Correlates of Late Drug-Eluting Stent Thrombosis: Strut Coverage as a Marker of Endothelialization”
To the Editor:
We have carefully read the interesting article of Finn et al1 that focused on the pivotal issue of late stent thrombosis in drug-eluting stents. From a registry of 81 human autopsies comprising 109 coronary lesions treated with drug-eluting stents, the authors identified 28 lesions with thrombus formation. They concluded that the most powerful predictor of stent thrombosis is the ratio of uncovered to total struts per section. Some points, in our opinion, deserve further clarification.
First, the main inclusion criterion was stent insertion at least 30 days before the event. Time since stent insertion varied widely among patients (254±235 and 244±289 days in those with and without thrombus, respectively). Secondly, in those with evidence of thrombus, clear knowledge of antiplatelet status was available in 18/23 patients, and only 11/18 (61%) were on dual antiplatelet therapy, 4 were on aspirin alone, 1 was on clopidogrel alone, and 2 were without antiplatelet therapy at all. The data in Tables 1 and 2 of the article by Finn et al1 appear inconsistent with the reported values in the text for both sets of data. This is important because the inclusion of patients with such different stent duration and/or antiplatelet status may have introduced a confounding factor. It is possible that different pathological mechanisms underlie stent thrombosis at 1 month and at 2 years. Our concern is the suitability of analyzing these heterogeneous conditions together.2
We have previously shown that aspirin withdrawal in patients with implanted stents was associated with a very high risk of adverse events, with an odds ratio of 89.78 (95% confidence interval 29.90 to 269.60).3 Dual antiplatelet therapy is now routine after coronary stent implantation, particularly after drug-eluting stent use.4 Drawing conclusions from a small registry in which half of the patients were not treated according to current guidelines may be misleading.
The authors1 analyzed an average of 5.3±2.7 sections per stent, thus appraising, in some cases, a small number of sections. In these cases, which sections did they select, and according to which criteria? This point, in our opinion, undermines the interesting conclusion that the middle section of a drug-eluting stent, rather than the proximal or distal ends, was the most common location of uncovered struts and thrombus formation. We wonder whether this conclusion would be confirmed in a larger and more homogeneous set of coronary sections.
We acknowledge the important work of Finn et al,1 but caution is required when extrapolating such focused examinations to the general population.
Finn AV, Joner M, Nakazawa G, Kolodgie F, Newell J, John MC, Gold HK, Virmani R. Pathological correlates of late drug-eluting stent thrombosis: strut coverage as a marker of endothelialization. Circulation. 2007; 115: 2435–2441.
Daemen J, Wenaweser P, Tsuchida K, Abrecht L, Vaina S, Morger C, Kukreja N, Juni P, Sianos G, Hellige G, van Domburg RT, Hess OM, Boersma E, Meier B, Windecker S, Serruys PW. Early and late coronary stent thrombosis of sirolimus-eluting and paclitaxel-eluting stents in routine clinical practice: data from a large two-institutional cohort study. Lancet. 2007; 369: 667–678.
Biondi-Zoccai GGL, Lotrionte M, Agostoni P, Abbate A, Fusaro M, Burzotta F, Testa L, Sangiorgi G. A systematic review on the hazards of aspirin discontinuation among 50279 patients with or at risk for coronary artery disease. Eur Heart J. 2006; 27: 2667–2674.
Smith SC Jr, Feldman TE, Hirshfeld JW Jr, Jacobs AK, Kern MJ, King SB 3rd, Morrison DA, O’Neill WW, Schaff HV, Whitlow PL, Williams DO. ACC/AHA/SCAI 2005 guideline update for percutaneous coronary intervention: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/SCAI Writing Committee to Update the 2001 Guidelines for Percutaneous Coronary Intervention). Available at: http://www.acc.org/clinical/guidelines/percutaneous/update/index.pdf. Accessed March 8, 2007.