Dr. Abela and colleagues correctly point out that the use of ethanol, a dehydrating agent, in the preparation of the coronary thrombi samples for scanning electron microscopy may have dissolved cholesterol crystals and led to an underestimation of the true content of cholesterol crystals in the coronary thrombi retrieved by thromboaspiration.
The study by Abela et al. (1) demonstrated that the use of vacuum dehydration of tissues is likely the preferred technique to study the impact of cholesterol crystals on biological membranes in vitro. In our study (2), we focused on the 2 main pharmacological therapeutic targets in acute coronary syndromes that can be visualized by microscopy, platelets, and fibrin fibers. Therefore, we preferred to use the ethanol dehydration technique instead of vacuum dehydration, to avoid the shrinkage and distortion of fibrin fibers that can occur with the latter technique. It was important to understand how the coronary thrombi evolve in time to understand the usefulness of treatments, such as fast-acting P2Y12 inhibitors or glycoprotein IIb/IIIa inhibitors, and their optimal use in the time course of the event.
However, the hypothesis of cholesterol crystals perforating the intima and being the underlying mechanism of plaque rupture is seductive and deserves more in vivo studies. Unfortunately, no currently available technology can detect cholesterols crystals in vivo in patients experiencing acute coronary syndromes, and even though angioscopy has been used to define thrombus colors, the lack of magnification and 3-dimensional analysis as provided by scanning electron microscopy does not allow the identification of such small structures (3).
Finally, it must be considered that the thromboaspiration technique does not allow a transversal analysis from 1 side of the artery to the other, as done in histological analysis of postmortem coronary arteries, but is most likely to retrieve a piece of the thrombus in the inner lumen, distant from the site of plaque rupture and therefore with fewer cholesterol crystals. This difference, added to the possibility of cutting-induced translocation of cholesterol crystals from the plaque itself to the inner lumen during tissue preparation, could be an explanation for the discrepancies in the amount of cholesterol crystals found in our study.
Acknowledgments
Please note: Dr. Silvain has received research grants from Sanofi-Aventis, Daiichi-Sankyo, Eli Lilly, Brahms, INSERM, Federation Francaise de Cardiologie, and the Societe Francaise de Cardiologie; consulting fees from Daiichi-Sankyo and Eli Lilly; and speaker honoraria from AstraZeneca, Daiichi-Sankyo, Eli Lilly, Iroko Cardio, and Servier. Dr. Montalescot has received research grants from Abbott Vascular, AstraZeneca, ITC Edison, Medtronic, Pfizer, Sanofi-Aventis, Servier, Societe Francaise de Cardiologie, Stago, Bristol-Myers Squibb, Boston Scientific, Cordis, Eli Lilly, Federation Francaise de Cardiologie, Fondation de France, Guerbet Medical, and INSERM; and consulting fees from AstraZeneca, Pfizer, Sanofi-Aventis, Bayer, Boehringer Ingelheim, Cardiovascular Research Foundation, Cleveland Clinic Research Foundation, Daiichi-Sankyo, Duke Institute, Europa, Lead-Up, GlaxoSmith-Kline, Institut de Cardiologie de Montreal, Menarini, Nanospheres, Novartis, Portola, The Medicines Company, TIMI Study Group, and Eli Lilly. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
References
- 1.Abela GS, Aziz K, Vedre A, Pathak D, Talbott JD, DeJong J. Effect of cholesterol crystals on plaques and intima in arteries of patients with acute coronary and cerebrovascular syndromes. Am J Cardiol. 2009;103:959–68. doi: 10.1016/j.amjcard.2008.12.019. [DOI] [PubMed] [Google Scholar]
- 2.Silvain J, Collet J-P, Nagaswami C, et al. Composition of coronary thrombus in acute myocardial infarction. J Am Coll Cardiol. 2011;57:1359–67. doi: 10.1016/j.jacc.2010.09.077. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Uchida Y, Uchida Y, Sakurai T, et al. Characterization of coronary fibrin thrombus in patients with acute coronary syndrome using dye-staining angioscopy. Arterioscler Thromb Vasc Biol. 2011;31:1452–60. doi: 10.1161/ATVBAHA.110.221671. [DOI] [PubMed] [Google Scholar]