No effect of PCSK9 inhibitors on D-dimer and fibrinogen levels in patients with familial hypercholesterolemia

Statins are generally believed to have cardiovascular protective effects independent of low-density lipoprotein-cholesterol (LDL-C) lowering, such as antithrombotic effects characterized by a decrease in D-dimer levels. For the recently introduced Proprotein convertase subtilisin/kexin 9 (PCSK9) inhibitors antithrombotic effects are yet unknown. We determined the effect of starting PCSK9 inhibitors on D-dimer and fibrinogen levels as most robust markers for thrombogenicity in statin-intolerant patients with familial hypercholesterolemia. We determined D-dimer and fibrinogen levels before and after start of evolocumab (n = 19) or alirocumab (n = 11). Baseline median D-dimer levels were 0.34 mg/L (IQR 0.24-0.59 mg/L) and baseline median fibrinogen levels 3.2 g/L (IQR 2.88-3.63 g/L). At follow-up D-dimer levels (median 0.31 mg/L (IQR 0.25-0.59 mg/L); p = 0.37), and fibrinogen levels (median 3.4 g/L (IQR 2.98-3.62 g/L); p = 0.38) did not change significantly. We therefore conclude PCSK9 inhibitors do not seem to have a profound antithrombotic effect, although a more subtle effect can not been excluded.