Background: Reticulated platelets (RP) represent young, hyperactive platelets, with increased mean volume and a greater number of dense granules than older circulating platelets. RP have been shown to increase in situations of increased platelet turnover, such as acute myocardial infarction (MI) and stroke. We have recently shown that the proportion of circulating RP inversely correlates with response to anti-platelet medication after ST-elevation MI (STEMI). However, data is lacking with regards to the long-term dynamics in levels of RP. Our aim was to examine the long term levels of RP after STEMI and the association with platelet reactivity.
Methods: Patients with STEMI treated with primary percutaneous intervention and prasugrel were tested for levels of RP using flow cytometry with Thiazole Orange staining. Additionally, platelet reactivity was assessed using the VerifyNow P2Y12 assay and the Multiplate analyzer. Tests were performed at baseline, one month after and six to twelve months following the acute event.
Results: Forty-six patients were included (mean age 56.5±5.5, 25% women, 17% diabetes). Levels of RP were 17.1±6.1% at baseline,13.1±9.7% after one month and 12.7±7.5% after 6-12 months (average 10.2±3 months, 30.4% current follow-up) after the STEMI (P=0.057 for comparison of RP levels at last and first exams). Overall, taking the 3 time-points together, platelet reactivity was strongly correlated with levels of RP according to VerifyNow PRU (Pearson’s r=0.45. See figure) and moderately correlated according to VerifyNow percent inhibition (r=-0.38).
Conclusions: There is a trend for a gradual decrease in levels of RP following STEMI. This may be clinically important, and associated with the well-established reduced incidence of thrombotic events at later stages after an acute MI. Further, larger studies are warranted to assess the clinical significance of this phenomenon.
