The old and the new: the pivotal role of TTE in TAVI

Transcatheter aortic valve implantation (TAVI) has undeniably revolutionised the field of interventional cardiology regarding the treatment of aortic stenosis (AS). With promising outcomes from the recently published PARTNER 2 trial (1), involving patients at intermediate risk for surgical treatment, further growth of an already rapidly expanding field is expected. Echocardiography has a pivotal role in transcatheter therapies from the early steps when the clinical diagnosis of a valvular disease is made to the postprocedural long-term follow-up. Although the role of transoesophageal echocardiography (TOE) for either pre-procedural planning or intraoperative guidance in TAVI has been the subject of several reviews and debates, the role of the older member of the family, transthoracic echocardiography (TTE), has not been given the attention it deserves. In this issue of Echo Research and Practice, Fryearson and coworkers review the role of TTE before and following TAVI and discuss as how it helps inform clinical decision-making in TAVI (2). TTE remains the main imaging modality of choice in the diagnosis of severe aortic stenosis and is initially used for screening TAVI candidates. There are also other echocardiographic parameters that may have potential impact on TAVI outcomes such as left ventricular (LV) function and concomitant valvular disease that are discussed in detail in the review article (2). Bicuspid aortic valve, although not an absolute contraindication for TAVI, has important implications such as a higher risk of paravalvular aortic regurgitation (PAR) (3) and an increase in permanent pacemaker requirements (4). The extent and distribution of aortic valve calcification is known to be a predictor of successful valve deployment and outcome and can be assessed by TTE. Notably, significant septal hypertrophy, which can be detected by TTE and may result in dynamic left ventricular outflow tract (LVOT) obstruction, is a contraindication to TAVI. However, TTE falls short in assessing the aortic valve annulus, which is key to procedural planning. Advances in three-dimensional (3D) imaging have led to the understanding that in the majority of cases, the LVOT and aortic annulus are elliptical and that any measurement of the annulus diameter obtained by TTE in the parasternal long-axis view often reflects the minor axis. Therefore, either 3D TOE or multi-slice computed tomography is routinely used to guide TAVI valve sizing. Furthermore, the assumed circular geometry of the LVOT in the continuity equation may result in an underestimation of aortic valve area, a recognised source of error and uncertainty in grading …