Invited Commentary

Abstract

Transcatheter aortic valve (AV) implantation is being increasingly used to treat high-risk or inoperable patients with severe aortic stenosis [1Webb J.G. Pasupati S. Humphries K. et al.Percutaneous transarterial aortic valve replacement in selected high-risk patients with aortic stenosis.Circulation. 2007; 116: 755-763Crossref PubMed Scopus (933) Google Scholar]. Although the surgically implanted AV prosthesis is sewn in place, the prothesis used for transcatheter AV implantation relies on good sizing and apposition to maintain position in the left ventricular outflow tract as well as functional integrity. In contrast to surgical AV replacement, where sizing is performed under direct vision, imaging of the aortic root is mandatory for sizing before transcatheter AV implantation. The aortic annulus on which such sizing is based can be defined as a virtual ring with three anatomic anchors at the nadir of each AV leaflet (ie, the three caudal points of the crown-shaped line of attachment of the leaflets) [2Schultz C.J. Moelker A. Piazza N. et al.Three dimensional evaluation of the aortic annulus using multislice computer tomography: are manufacturer's guidelines for sizing for percutaneous aortic valve replacement helpful?.Eur Heart J. 2010; 31: 849-856Crossref PubMed Scopus (152) Google Scholar]. Patient matrices provided by the manufacturers and used in clinical practice to select the valve size are usually based on the annulus dimension as defined by transthoracic or transesophageal echocardiography. However, these techniques produce 2-dimensional tomograms, whereas the aortic root has a complex 3-dimensional geometry, with the base (the annulus) often elliptical. Therefore, differences in the minimal and maximal diameters can lead to substantial differences in the selection of prosthesis size, which may result in undersizing or oversizing. In contrast, with a 3-dimensional imaging modality, such as multislice computed tomography, multiple axial diameter measurements of the noncircular annulus are possible [2Schultz C.J. Moelker A. Piazza N. et al.Three dimensional evaluation of the aortic annulus using multislice computer tomography: are manufacturer's guidelines for sizing for percutaneous aortic valve replacement helpful?.Eur Heart J. 2010; 31: 849-856Crossref PubMed Scopus (152) Google Scholar]. de Heer and colleagues [3de Heer L.M. Budde R.P.J. van Prehn J. et al.Pulsatile distension of the nondiseased and stenotic aortic valve annulus: analysis with electrocardiogram-gated computed tomography.Ann Thorac Surg. 2012; 93: 516-522Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar] analyzed computed tomography images of 15 individuals without AV disease and 20 patients with severe aortic stenosis and demonstrated significant area and radius changes throughout the cardiac cycle in both the nondiseased and stenotic aortic annulus. Although this study is limited by its small population, the large age difference between the two groups, and the slightly different scan protocols, it further confirms the elliptical shape of the aortic annulus. More important, even in patients with severe aortic stenosis, this annulus is not completely rigid but displays significant radius changes over the cardiac cycle. Knowledge of such a time-varying elliptical shape of the AV annulus should help in future prosthesis design and contribute to improved patient outcome. Pulsatile Distention of the Nondiseased and Stenotic Aortic Valve Annulus: Analysis With Electrocardiogram-Gated Computed TomographyThe Annals of Thoracic SurgeryVol. 93Issue 2PreviewKnowledge of the dynamic changes of the aortic valve (AV) annulus may aid in the sizing and design of transcatheter valve prostheses. We assessed AV annulus distention in patients without AV disease and with severe AV stenosis (AS) using computed tomography (CT). Full-Text PDF