Transcatheter heart-valve replacement: update

Abstract

Key points• Transcatheter valve replacement offers patients less invasive heart-valve therapy, with lower morbidity and mortality, and quicker recovery. A dedicated team is essential for the success of this program.• The procedure can be performed for the aortic and pulmonic valves.• Minimally invasive techniques enable valve implantation, as well as repeat valve replacement, without the need for cardiopulmonary bypass or sternotomy.Previously published at www.cmaj.caReview replacement is considered high risk. 6 Certain conditions, such as a highly calcified (i.e., "porcelain") aorta, mediastinal irradiation, liver cirrhosis or a need for reoperation with patent bypass grafts, may lower the threshold of risk for transcatheter valves, because of the well-recognized increased risks associated with these conditions in conventional surgery.Transcatheter therapy is usually not offered to patients with asymptomatic aortic stenosis or patients with a life expectancy of less than one year. Although most patients will have a suitably sized aortic annulus (as assessed by echocardiography), patients with a large aortic annulus are not currently candidates for transcatheter aortic valve implantation because of a limited selection of prosthetic sizes. Our current indications and contraindications for transcatheter aortic valve implantation are detailed further in Box 1. An ongoing randomized clinical trial in Europe and North America is expected to further delineate the optimal patient groups for transfemoral and transapical aortic valve therapy. 7 Transcatheter pulmonic valve replacement is indicated in patients with congenital, symptomatic pulmonary valve stenosis or insufficiency who have previously undergone right ventricular outflow tract reconstruction, usually for tetralogy of Fallot. The most common indication is homograft stenosis with calcification. Most patients are young (in contrast to transcatheter aortic valve patients), but have undergone multiple previous operations and are therefore deemed to be at increased risk with conventional surgery. Preoperative workupA history and physical examination, as well as routine preoperative blood work, 12-lead electrocardiography, and chest radiography, are performed initially to assess the patient's candidacy for transcatheter valve therapy. Transthoracic echocardiography defines the character and severity of the aortic stenosis. However, transesophageal echocardiography is often necessary to better delineate the calcification pattern and accurately measure the aortic annulus and root diameters. Currently, limitation in the sizes of prostheses require patients to have a specific aortic annulus diameter for proper stent deployment and seating (Box 1). To decrease the risk of paravalvular leak, the implanted prosthesis is slightly oversized. Because of the advanced age of the patients, coronary angiography is performed. Computed tomography is also recommended for all patients to define the distances between the aortic annulus and the coronary ostia, to minimize risks of cor...

The critical role of imaging navigation and guidance in transcatheter aortic valve implantation

“…Although most centers use preoperative computed tomography (CT) to assess patient candidacy, intraoperative guidance consists of aortography for positioning and transesophageal echocardiography for functional assessment. 6,7 Neither of these modalities is optimal for guidance. Aortography provides good stent delineation but lacks 3-dimensional context and provides only limited views of the aortic valve and coronary ostia.…”