Quantification of paravalvular regurgitation after transcatheter aortic valve implantation: improved accuracy means better standardization.

Aortic stenosis (AS) is the most common valvular heart disease in western countries. Because of the ageing population, AS is being an increasing health problem with sizeable economic impact. AS is a gradually progressive disease, characterized by a long asymptomatic phase, lasting several decades, followed by a shorter symptomatic phase associated with severe narrowing of the orifice of the aortic valve. Once symptoms occur, the prognosis is poor and without treatment; patients usually die within 2–3 years. Surgical aortic valve replacement is considered the standard treatment for symptomatic AS. Transcatheter aortic valve implantation (TAVI) has recently emerged as an alternative therapy for patients with severe AS who are not candidates for surgery or are at high risk for complications due to surgery. TAVI is non-inferior to surgery in terms of early and mid-term mortality and is likely to be superior if the patient has vascular anatomy and vessels that are healthy enough to be treated with the use of a transfemoral approach. However, despite its favourable haemodynamics, paravalvular aortic regurgitation (PVAR) is common after TAVI. PVAR is an independent predictor of shortand long-term mortality, though the impact of mild regurgitation remains controversial. The accurate assessment of PVAR severity is warranted but remains challenging. Doppler echocardiography is the most used imaging technique to assess AR severity. The origin and direction of the jets should be evaluated. The optimal views for detection of regurgitant jets include the parasternal long-axis, short-axis (SAX), apical long-axis, and five-chamber views. Because PVAR jets travel along the natural curvature of the prosthesis annular interface (eccentric jets), imaging in multiple planes including off-axis views is necessary. Colour Doppler evaluation should be performed just below the valve stent for paravalvular jets and at the coaptation point of the leaflets for central regurgitation. The entire circumference of the valve ring must be assessed using the parasternal short-axis view. Apical views should thus be carefully examined to properly detect and quantitate potential posterior jets that maybe missed in the parasternal views (shadowing effect of the stent). Generally, the same principles and methods used for quantification of other prosthetic valves are used with determination of flow convergence zone, measurement of the vena contracta, and extent of regurgitation into the left ventricle and spectral Doppler parameters such as the pressure half-time and diastolic flow reversal into the descending aorta. However, there are very limited data on the application and validation of these parameters (e.g. vena contracta width, effective regurgitant orifice area, regurgitant volume) in the context of TAVI. Recently, the Valve Academic Research Consortium (VARC) has revisited the echocardiographic criteria for defining PVAR severity after TAVI. The VARC-II adopted the SAX criterion as ‘critical’ in assessing the number and severity of paravalvular jets. With this approach, identification of the true neck of the jet is mandatory. Due to the complexity of certain PVARs and the limitation of the echocardiography in certain situations (acoustic shadowing, eccentric jets, multiple jets), the evaluation of the PVAR might need to be completed with other imaging techniques [3D echocardiography, cardiac magnetic resonance (CMR), computed tomography (CT), invasive angiography]. 3D echocardiography, especially during transoeophageal echocardiography, is ideal for imaging the entire aortic prosthesis, the whole ring, and the extent of paravalvular leak. Limited echocardiographic windows, tissue dropout, poor temporal resolution, and the lack of validated data are the commonest limitations of 3D echocardiography. ECG-gated CT with 3D reconstruction is a promising tool in PVARs evaluation. CMR might be a useful supplement to echocardiography and might be the modality of choice when there is discordance in grading from different echocardiographic windows. However, the lack of evidence, inconsistency of definitions of PVAR severity, and its limited availability represent the main limitations to the widespread use of CMR for assessing AR after TAVI. After implantation, the angiographic grading of PVAR is an easy-to-use method. PVAR can be classified