The relationship between the type of thrombus content and mean platelet volume in predicting reperfusion outcomes

To the Editor

We read the manuscript written by Pereg et al. [1] with great interest in a recent issue of your journal. In their study, the authors aimed to find out whether there is an association between mean platelet volume (MPV) values at admission and reperfusion failure in patients with ST elevated myocardial infarction (STEMI) treated with thrombolysis. The prevalence of thrombolysis failure was significantly higher in patients with MPV > 8.6 fl compared to those with MPV ≤ 8.6 fl (p = 0.048). The authors claimed that higher MPV correlated with thrombolysis failure in patients presenting with STEMI. The authors also added that while most cases of failed reperfusion occurred in the high MPV group, 30% of them occurred in the low MPV group. We want to affirm our findings from a study [2] that concerns similar subjects, which was conducted on a selected patient group.

The aim of our study was prospectively assessing the value of MPV, which is a simple and accurate measure of the functional status of platelets, in patients hospitalized with diagnosis of acute coronary syndromes (ACS). A total of 216 consecutive patients (156 male, 60 female) hospitalized with the diagnosis of non-ST segment elevation (NSTE) ACS within the first 24 hours of chest pain were enrolled as the study group, while 120 patients, matched according to sex and age, with stable coronary heart disease (CHD) (85 male, 35 female) were enrolled as a control group. Then study patients were classified into two groups: those with unstable angina (USAP, n = 105) and those with non-ST segment elevation myocardial infarction (NSTEMI, n = 111). The mean MPV values reported with standard deviations were 10.4 ± 0.6 fL, 10 ± 0.7 fL, 8.9 ± 0.7 fL consecutively for NSTEMI, USAP and stable CHD with significant differences. Patients with ischemic attacks in the first day of hospitalization accompanied by >0.05 mV ST segment shift had significantly higher MPV compared to those without such attacks (P = 0.001). Multivariable logistic regression analysis yielded that MPV (P = 0.016), platelet count (P < 0.001), and the presence of >0.05 mV ST segment depression at admission (P = 0.002) were independent predictors of development of NSTEMI in patients presenting with NSTE ACS. The number of critically stenosed coronary arteries (>70% for anterior descending, circumflex and right coronary arteries) was not different between NSTEMI and USAP. Besides classifying ACS patients according to presence of three-vessel disease, there was no significant difference in terms of MPV (10.1 ± 0.7 for both).

In their recent trial, Celebi et al. [3] also investigated the same subject and found a linear relationship between TIMI frame count and high MPV in patients who were treated with thrombolysis for STEMI. The results of our study showed that MPV is not related to severity of coronary atherosclerosis but the severity of acute coronary occlusion. So, higher MPV values are not unexpected in STEMI. However, we enrolled patients with NSTEACS while two other authors enrolled STEMI patients. There is a critical difference that involves thrombus contents. In NSTEACS, thrombus content is supposed to be platelet-rich while it is fibrin-rich in STEMI [4]. The relationship between the response to mechanical reperfusion and MPV is established [5]. In mechanical reperfusion, thrombus is directly degraded by balloon whereas medical thrombolysis (fibrinolysis) targets fibrin and other soluble coagulation factors rather than platelets. We suggest that additional data comparing MPV with serum levels of fibrin degrading products, plasminogen activator inhibitor-1 (which impedes fibrinolysis) and prothrombin (which strengthens fibrin structure) would help authors to reach more definite conclusions.