Abstract 12563: The Trajectory of Platelet Factor 4 in Acute Myocardial Infarction and the Impact of PCSK9-Inhibition

Abstract

Introduction: Increased platelet activity during the peri- and early post-infarction period may contribute to adverse outcomes during that time. Platelet factor 4 (PF4) promotes coagulation and inflammation. The trajectory of PF4 and the impact of proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition on that trajectory are unknown. Hypothesis: Early administration of the PCSK9 inhibitor evulocumab, added to dual anti-platelet therapy, inhibits a rise in PF4 during the early post-infarction period. Methods: Participants from the Evolocumab in Acute Coronary Syndrome trials (EVACS; NCT03515304, NCT04082442), with a NSTEMI and a troponin-I of > 5 ng/ml or a STEMI were randomized to placebo or to 420 mg SQ of evolocumab within 24 hours of hospitalization. We performed serial ex vivo serum PF4 levels obtained at baseline (prior to study drug administration), and at days 1 and 30 and PF4 values were normalized to total platelet count. Normally distributed data were summarized using means and standard deviations and non-normally distributed data using medians and interquartile ranges. Results: Twenty-three participants were randomized to placebo and 23 to evolocumab. Mean age was 60±13 years, 48% were women, 22% were African American and 96% were on dual anti platelet therapy. Baseline PF4 concentrations (expressed as ng/1k platelets) did not differ between the two groups (placebo: 9.3 [4-12] vs evolocumab 8.0 [4-12], p=0.8). There was no significant change in PF4 in the placebo group from baseline to day 1 but a significant increase to 13.0 [11-14], p<0.01 (baseline vs 30 days) at 30 days (+32%). In contrast, there were no significant changes from baseline in the evolocumab group at either of the timepoints. At 30 days PF4 was higher in the placebo group 13.06 [11-14] than the evolocumab group 10.7 [6-13], p=0.04. Further analysis of results in the evolocumab group did not show any significant changes in PF4 based on the type of P2Y12 inhibitor used and no association with the change in LDL-cholesterol. Conclusion: A rise in PF4 levels was observed during the early post-infarction period in acute myocardial infarction patients. This rise was reversed by a single 420 mg SQ dose of evolocumab administered within 24 hours of hospital admission.