Letter by Testa et al Regarding Article, “Presence of Older Thrombus Is an Independent Predictor of Long-Term Mortality in Patients With ST-Elevation Myocardial Infarction Treated With Thrombus Aspiration During Primary Percutaneous Coronary Intervention”
To the Editor:
We read with interest the article by Kramer et al1 assessing the possible relationship between thrombus age and outcome in patients with ST-elevation myocardial infarction treated with primary percutaneous coronary intervention and undergoing thrombus aspiration. The authors concluded that thrombus age is an independent predictor of an adverse outcome. However, in our opinion, several issues require further insights.
First, different aspiration devices have been used (Rescue, Export, and Proxis), each with its own features and capacity of retrieving material. As a consequence, different amounts of thrombus have been aspirated. In the analysis, the quantity of retrieved thrombus and its initial extent have been neglected. Yet we believe that this measurement is pivotal because the plaque/thrombus burden highly affects the risk of distal embolization and is correlated with subsequent risk of future events.2 The mere angiographic assessment of the distal embolization/no-reflow phenomenon, which has been visually evaluated and therefore not systematically calculated, might be insufficient.
Second, although the thrombus age has been assessed according to an established definition, we believe that the dichotomous classification of either “fresh” or “older” might be an oversimplification when translated into clinical practice. More specifically, it is conceivable that, instead of just 2 categories, an accurate analysis requires a wider spectrum that would better reflect the histopathology of such a complex matter while adding further complexity.
Third, the major end point of all-cause death at 4 years sounds questionable. It is hard to correlate a histopathological finding with the probability of all-cause mortality that might be related to a number of conditions. What is the factual link between the aspirated material and a fatality occurring within the next 4 years? A restricted end point such as cardiac death would have sounded more appropriate.
Fourth, in the uni- and multivariate regression analyses, the levels of creatine kinase-MB and troponin are missing. They largely affect the outcome.3 Although this article is original and interesting, several issues highlight the hurdles of translating the findings of basic science into practice.
Kramer MC, van der Wal AC, Koch KT, Ploegmakers JP, van der Schaaf RJ, Henriques JP, Baan J Jr, Rittersma SZ, Vis MM, Piek JJ, Tijssen JG, de Winter RJ. Presence of older thrombus is an independent predictor of long-term mortality in patients with ST-elevation myocardial infarction treated with thrombus aspiration during primary percutaneous coronary intervention. Circulation. 2008; 118: 1810–1816.
Alfonso F, García P, Pimentel G, Hernández R, Sabaté M, Escaned J, Bañuelos C, Fernández C, Macaya C. Intravascular ultrasound study: predictors and implications of residual plaque burden after coronary stenting: an intravascular ultrasound study. Am Heart J. 2003; 145: 254–261.
Antman EM, Hand M, Armstrong PW, Bates ER, Green LA, Halasyamani LK, Hochman JS, Krumholz HM, Lamas GA, Mullany CJ, Pearle DL, Sloan MA, Smith SC Jr. ACC/AHA guidelines for the management of patients with ST-elevation myocardial infarction: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Revise the 1999 Guidelines for the Management of Patients With Acute Myocardial Infarction) developed in collaboration with the Canadian Cardiovascular Society. J Am Coll Cardiol. 2008; 51: 210–247.