Microparticles are small cell fragments that can induce fat plaques, calcification and formation of thrombus. They can be released through multiple stimulations, but also the high flow of blood through partially obstructed aortic valves.

In patients with severely obstructed aortic valves the investigators hypothesize that microparticles levels will be elevated and that they will go down after percutaneous treatment of the valves.

Microparticle (MPs) levels and subtypes according to endothelial cell, macrophage and platelet markers will be measured by flow-cytometry using appropriate fluorochromes. Patient baseline (including measures of severity of aortic stenosis and its calcification), procedural data, and clinical evolution will be collected. Inflammatory markers will be measured, which along with clinical date will be tested for correlation with microparticle levels.

Patients MPs will be measured before and after percutaneous treatment of the severe aortic stenosis.

Inclusion Criteria:

• Clinical indication to be treated with transcatheter aortic valve replacement.

Exclusion Criteria:

• Non native aortic valve
• Moderate aortic regurgitation
• The following complications following valve implantation: patient instability, need for vasoactive pressors, sepsis and severe infections, stroke.