2 The condition, current treatments and procedure
2.1 The 2 main indications for aortic valve replacement are aortic stenosis and aortic regurgitation. Symptoms of both conditions typically include shortness of breath and chest pain on exertion. The increased cardiac workload can lead to heart failure.
2.2 Aortic valve replacement with an artificial prosthesis (biological or mechanical) is the conventional treatment for patients with severe aortic valve dysfunction. Valves may be placed by either open heart surgery or using transcatheter aortic valve implantation (TAVI). Although bioprosthetic valves have some advantages over mechanical valves, they may degenerate and fail over time. The standard treatment for a failed bioprosthetic valve is open heart surgery, with a further valve replacement. Reoperative surgery is associated with significant morbidity and a higher risk of mortality than primary surgery.
2.3 Valve-in-valve (ViV) TAVI has been developed as a less invasive alternative treatment that avoids the need for cardiopulmonary bypass. It can be used for treating failed bioprosthetic aortic valves originally placed by either open heart surgery or TAVI.
2.4 The procedure is done with the patient under general or local anaesthesia with sedation, using fluoroscopy. Prophylactic antibiotics and anticoagulant medication are used.
2.5 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.
2.6 The procedure is technically similar to TAVI for aortic stenosis into a native aortic valve, but some modifications to the technique have been reported. The new prosthetic valve is placed tightly into the orifice of the failed bioprosthetic valve, pushing the old valve leaflets aside. Gradual valve deployment (without rapid inflation of the balloon) is done and angiography is used to ensure accurate positioning of the valve. The old prosthesis is also used as a guide for positioning the new valve. The external diameter of the new valve should usually match or exceed the internal diameter of the old valve. Anticoagulation or antiplatelet therapy may be continued after the procedure.