Novel Echocardiographic and Invasive Haemodynamic Measurements in the Assessment of Patients Low Flow Low Gradient Aortic Stenosis Undergoing TAVI

Participants will have a routine ultrasound of the heart (echocardiogram) before the procedure. During this test we will take a few extra measurements, this will not add any significant time to the scan

During the TAVI procedure 3 catheters (tubes) will be inserted into the blood vessels at the top of the participants legs as per normal standard care (there will be no extra skin punctures as part of the study).

Participants will have a soft study wire inserted to measure the pressure in the left ventricle. This step is in addition to standard care.

Participants will have chests x-ray when the soft study wire is inserted.

Participants will be given a low dose infusion of dobutamine, to make the heart pump quicker and more vigorously.. This will last for approximately 5 minutes