August 30, 2012 Leave a comment
submitted by Dr Gokulnath Rajendran & Dr Stephen T Webb both at Papworth Hospital NHS Foundation
Aortic stenosis (AS) is the most common type of valvular heart disease in developed countries. It is a progressive disease and the incidence of
severe stenosis increases with age, ~2% at 65 years and 4% at 85 years. Patients may be asymptomatic or present with syncope, angina or exertional breathlessness. Surgical replacement of aortic valve is the standard treatment to improve quality of life in symptomatic severe AS. However patients who are considered too high risk for surgery could benefit from minimally invasive transcatheter aortic valve implantation (TAVI).
TAVI was first performed in 2002. Since then, technology has evolved rapidly and in the last decade, more than 50,000 procedures have been performed worldwide2. The procedure involves balloon valvuloplasty of the stenosed valve followed by deployment of a bioprosthetic valve by transfemoral or transapical route.
In UK, TAVI is currently performed in cardiac catheterisation suites with operating theatre facilities (‘hybrid’ catheter rooms) in specialist cardiothoracic centres by interventional cardiologists. Patients undergo comprehensive investigations including echocardiography, coronary angiography and computed tomographic (CT) angiography. Multi-disciplinary assessment of the patient is essential prior to the procedure.
Although TAVI can be performed under local anaesthesia, the majority of patients receive general anaesthesia. General anaesthesia provides
the patient immobility and facilitates the use of transoesophageal echocardiography. Anaesthetic management can be potentially challenging as these patients often have multiple comorbidities. The procedure involves rapid ventricular transvenous pacing to temporarily reduce cardiac motion. Pacing wires are inserted in case of bradyarrhythmias. Vasopressors are usually administered to treat intraoperative hypotension and maintain coronary perfusion pressure.
As the procedure may lead to potentially catastrophic haemodynamic instability, a cardiopulmonary bypass circuit and clinical perfusion team are kept on stand-by in the hybrid catheter room. Intraaortic balloon counterpulsation may be necessary to support patients with very poor ventricular function.
Complications of TAVI include delirium, seizure, stroke or TIA, myocardial infarction, cardiac arrhythmia, access site arterial injury and cardiac tamponade. Moderate to severe para-valvular regurgitation may occur after TAVI3.
Two-year survival rate is similar following TAVI compared to surgical procedure3 and is superior compared to medical treatment4. The UK National Institute for Health & Clinical Excellence (NICE) concluded that evidence for the efficacy of TAVI is sufficient to recommend the procedure for those unsuitable for surgery, but that there is0 insufficient evidence to support it for those considered suitable for surgery. Technological refinements could result in expansion of this less-invasive procedure to a broader spectrum of patients in the future.
1 Carabello BA, Paulus WJ. Aortic stenosis. Lancet 2009;373:956-66.
2 Vahanian A. Transcatheter aortic valve implantation: our vision of the future. Arch
Cardiovasc Dis. 2012 Mar;105(3):181-6.