Lack of Association Between Low Density Lipoprotein Particle Size and On-Treatment Platelet Reactivity in Patients With Coronary Artery Disease

Background and Objectives: Small dense low density lipoproteins (sd-LDL) are a risk factor for coronary artery disease and are known to stimulate platelet function in vitro. This study aimed to evaluate whether high proportion of sd-LDL is associated with high on-treatment platelet reactivity (HOPR). Subjects and Methods: From January 2009 to March 2010, 439 subjects (mean age: $64.3{\pm}9.7$, Male : Female=306 : 133) were enrolled from the low density LIPOProtein-cholesterol Size measurement Registry with coronary artery disease, who had undergone elective percutaneous coronary intervention and measured both LDL particle size and on-treatment platelet reactivity (OPR). Mean LDL particle size was measured by gradient gel electrophoresis (Quantimetrix, $Lipoprint^{TM}$) and OPR by the $VerifyNow^{TM}$ system (aspirin and P2Y12). Results: Between pattern A (large, buoyant LDL dominant) and B (sd-LDL dominant) population, there were no significant difference in OPR to aspirin ($441.3{\pm}71.9$ vs. $434.07{\pm}63.45$ aspirin reaction units, p=0.351) or clopidogrel ($237.9{\pm}87.3$ vs. $244.9{\pm}80.7$ P2Y12 reaction units, p=0.465). There was no difference in LDL particle size between patients with HOPR compared with non-HOPR patients (aspirin: $26.8{\pm}0.5$ vs. $26.7{\pm}0.6$ nm, p=0.078, clopidogrel: $26.7{\pm}0.6$ vs. $26.8{\pm}0.5$ nm, p=0.857). Pearson's correlation coefficients between LDL particle size and platelet reactivity were not statistically significant (aspirin assay: r=0.080, p=0.098, P2Y12 assay: r=-0.027, p=0.568). Conclusion: There was no significant association between LDL particle size and OPR in patients with coronary artery disease.