Transcatheter aortic valve implantation (TAVI) involves inserting a catheter into a blood vessel in your upper leg or chest and passing it towards your aortic valve. The catheter is then used to guide and fix a replacement valve over the top of the old one. This technique does not require the heart to be stopped and a heart-lung (bypass) machine doesn't need to be used. It is also far less invasive than a traditional valve replacement, as no large chest incision is required with this procedure.