Percutaneous valve replacements

Percutaneous valve intervention

• percutaneous valve interventions are being developed for patients considered to be at high risk for standard valve surgery
• transcatheter aortic valve implantation (TAVI) is used to treat severe symptomatic aortic stenosis
• transcatheter mitral valve intervention (the 'Mitraclip') is used to treat symptomatic mitral regurgitation
• transcatheter valve interventions should be delivered by an experienced multidisciplinary team within a hospital capable of doing cardiac surgery
• aortic valves replaced by TAVI do not require long term anticoagulation therapy

TAVI:

• Transcatheter aortic valve implantation (TAVI) is most commonly considered for patients who have degenerative, calcific AS
  • involves replacing the aortic valve via balloon expandable (the Edwards Sapien XT valve) or self-expanding (the Medtronic Corevalve) technologies. In effect, a new tissue valve (porcine or bovine), mounted on a stent, is positioned inside the native valve ring once the stenosed leaflets have been disrupted by balloon inflation
  • patient does not undergo a sternotomy, does not go onto cardiopulmonary bypass and the heart is beating throughout the procedure
  • generally the procedure is done under a general anaesthetic
  • new valve can be introduced via the femoral artery, apex of the heart, subclavian artery or upper mini-sternotomy
  • aortic valves replaced by TAVI do not require long term anticoagulation, but most patients will receive antiplatelet therapy. In the absence of comorbidities most patients are able to be discharged within a day or two of the procedure
  • NICE state that "..for patients with aortic stenosis who are considered to be unsuitable for surgical aortic valve replacement the evidence on the efficacy of TAVI is adequate.." (2)

Transcatheter implantation of the mitral valve

• used for repair of severe, symptomatic MR caused by either left ventricular dilation (functional regurgitation) or mitral valve prolapse with specific echo features
  • procedure involves using a 'clip' to tether the anterior and posterior mitral valve edges together at their mid points thereby creating a 'double orifice' mitral valve when open and a more competent valve when closed. Devices aimed at replacing the mitral valve completely are currently under development but are not yet being used in routine clinical practice

Reference:

• 1) British Heart Foundation (February 2012).
• 2) NICE (March 2012). Transcatheter aortic valve implantation for aortic stenosis