3 The procedure
3.1 The procedure is done with the patient under general or local anaesthesia, with imaging guidance using fluoroscopy and usually transoesophageal echocardiography. Prophylactic antibiotics and anticoagulant medication are given before and during the procedure. Temporary peripheral extracorporeal circulatory support (usually through the femoral vessels) is sometimes used.
3.2 A new prosthetic valve is mounted within a stent, which is either self-expanding or expanded using balloon inflation. It is delivered by a catheter across the failed bioprosthetic aortic valve. Access to the aortic valve can be achieved transluminally, with entry to the circulation through the femoral or other large artery (sometimes known as a percutaneous, or endovascular approach), or through apical puncture of the left ventricle (a transapical or transventricular approach). In the transluminal approach, surgical exposure and closure of the artery may be needed. How access to the aortic valve is achieved depends on whether there are factors that make the passage of a catheter through the circulation difficult, such as peripheral arterial disease.
3.3 The procedure is technically similar to transcatheter aortic valve implantation for aortic stenosis into a native aortic valve (see NICE interventional procedures guidance 421), but some modifications to the technique have been reported. Instead of dilating the failed aortic bioprosthetic valve with a balloon, the new prosthetic valve is attached tightly into the orifice of the failed bioprosthetic valve, pushing the old valve leaflets aside. The important modification is slow, gradual valve deployment (without rapid inflation of the balloon) with angiography to enable accurate positioning of the valve. The old prosthesis is used as a guide for positioning the new valve. The size of the new valve is usually selected so that its external diameter matches or exceeds the internal diameter of the old valve.