Endothelial, platelet, and macrophage microparticle levels do not change acutely following transcatheter aortic valve replacement.

Background: Patients with severe aortic stenosis have increased levels of prothrombotic and proinflammatory microparticles (MP), and MPs actively regulate pathological processes that lead to atherothrombotic cardiovascular events. Shear stress is a validated stimulus of MP production, and abnormal shear stress in aortic stenosis increases MP release in ex-vivo studies. We hypothesized that in patients with severe aortic stenosis, percutaneous replacement of the aortic valve (TAVR) would reduce abnormal shear stress and would decrease levels of circulating MPs.

Findings: The experimental protocol utilized flow cytometry (FC) and nanoparticle tracking analysis (NTA) to quantify circulating plasma MP levels in aortic stenosis patients at baseline and 5 days after TAVR. The baseline and 5 day MP counts measured by FC were 6.10⋅10(5) ± 1.21⋅10(5) MP/μL and 5.74⋅10(5) ± 9.54⋅10(4) MP/μL, respectively (p = 0.91). The baseline and 5 day MP counts measured by NTA were 9.29⋅10(13) ± 1.66⋅10(13) MP/μL and 3.95⋅10(14) ± 3.11⋅10(14) MP/μL, respectively (p = 0.91). When MPs were stratified by cell source, there was no difference in pre/post TAVR endothelial, platelet, or leukocyte MP levels.

Conclusion: Levels of circulating MPs do not change acutely following TAVR therapy for aortic stenosis. Trial registered at clinicaltrials.gov NCT02193035 on July 11, 2014.