The aim of this prospective registry is to compare invasive versus echocardiography-derived transvalvular gradients before and after TAVI with balloon-expandable THVs.All patients will undergo a transthoracic echocardiogram in the operating room prior to aortic valve implantation. In addition, two catheters (one in the ventricle and one in the aorta) will be used to invasively measure the transvalvular gradient both before and after aortic valve implantation. The invasive measurements will be performed in different positions of the ventricle and aorta simultaneously. At the end of the procedure, aortic gradient measurement by echocardiography shall be performed again. A maximal three months follow-up is expected.

Inclusion Criteria:

• Age ≥ 18 years and able to give consent
• Severe symptomatic native aortic valve stenosis with indication for TAVI according to 2021 ESC/EACTS Valvular Heart Disease Guidelines.
• Use of balloon-expandable THV
• Written informed consent

Exclusion Criteria:

• Emergency or urgent treatment indication
• Patients under hemodynamically unstable conditions.
• Previous bioprosthetic aortic valve implantation
• Patient cannot adhere to or complete the trial protocol for any reason

All consecutive patients with severe aortic valve stenosis undergoing TAVI with balloon-expandable transcatheter heart valves (THV).