Current definitions of hemodynamic structural valve deterioration after bioprosthetic aortic valve replacement lack consistency.

Objective: New echocardiographic definitions have been proposed for hemodynamic structural valve deterioration. We aimed to study their consistency in classifying structural valve deterioration after surgical aortic valve replacement. Methods: Data were used of patients undergoing surgical aortic valve replacement in a multicenter, prospective cohort study with a 5-year follow-up. All patients received the same stented bioprosthesis. Echocardiographic parameters were assessed by an independent core laboratory. Moderate or greater stenotic hemodynamic structural valve deterioration was defined according to Capodanno and colleagues, Dvir and colleagues, and the Valve Academic Research Consortium 3; regurgitation data were not considered in this analysis. Consistency was quantified on the basis of structural valve deterioration classification at subsequent time points. Results: A total of 1118 patients received implants. Patients' mean age was 70 years, and 75% were male. Hemodynamic structural valve deterioration at any visit was present in 51 patients (4.6%), 32 patients (2.9%), and 34 patients (3.0%) according to Capodanno, Dvir, and Valve Academic Research Consortium 3. A total of 1064 patients (95%) were never labeled with structural valve deterioration by any definition. After the first classification with structural valve deterioration, 59%, 59%, and 65% had no subsequent structural valve deterioration classification according to Capodanno, Dvir, and Valve Academic Research Consortium 3, respectively. Conclusions: The current definitions of hemodynamic structural valve deterioration are strong negative predictors but inconsistent positive discriminators for the detection of stenotic hemodynamic structural valve deterioration. Although the diagnosis of structural valve deterioration may be categorical, echocardiographic indices lack this degree of precision in the first 5 years after surgical aortic valve replacement. The inconsistency of current structural valve deterioration definitions impedes the detection of true valve degeneration, which challenges the clinical usefulness of these definitions.

On the role of aortic valve architecture for physiological hemodynamics and valve replacement, Part I: Flow configuration and vortex dynamics.

Aortic valve replacement has become an increasing concern due to the rising prevalence of aortic stenosis in an ageing population. Existing replacement options have limitations, necessitating the development of improved prosthetic aortic valves. In this study, flow characteristics during systole in a stenotic aortic valve case are compared with those downstream of two newly designed surgical bioprosthetic aortic valves (BioAVs). To do so, advanced three-dimensional fluid-structure interaction simulations are conducted and dedicated analysis methods to investigate jet flow configuration and vortex dynamics are developed. Our findings reveal that the stenotic case maintains a high jet flow eccentricity due to a fixed orifice geometry, resulting in flow separation and increased vortex stretching and tilting in the commissural low-flow regions. One BioAV design introduces non-axisymmetric leaflet motion, which reduces the maximum jet velocity and forms more vortical structures. The other BioAV design produces a fixed symmetric triangular jet shape due to non-moving leaflets and exhibits favourable vorticity attenuation, revealed by negative temporally and spatially averaged projected vortex stretching values, and significantly reduced drag. Therefore, this study highlights the benefits of custom-designed aortic valves in the context of their replacement through comprehensive and novel flow analyses. The results emphasise the importance of analysing jet flow, vortical structures, momentum balance and vorticity transport for thoroughly evaluating aortic valve performance.

On the role of aortic valve architecture for physiological hemodynamics and valve replacement, Part II: Spectral analysis and anisotropy.

Severe aortic valve stenosis can lead to heart failure and aortic valve replacement (AVR) is the primary treatment. However, increasing prevalence of aortic stenosis cases reveal limitations in current replacement options, necessitating improved prosthetic aortic valves. We investigate flow disturbances downstream of severe aortic stenosis and two bioprosthetic aortic valve (BioAV) designs using advanced energy-based analyses. Three-dimensional high-fidelity fluid-structure interaction simulations have been conducted and a dedicated and novel spectral analysis has been developed to characterise the kinetic energy (KE) carried by eddies in the wavenumber space. In addition, new field quantities, i.e. modal KE anisotropy intensity as well as normalised helicity intensity, are introduced. Spectral analysis shows kinetic energy (KE) decay variations, with the stenotic case aligning with Kolmogorov's theory, while BioAV cases differing. We explore the impact of flow helicity on KE transfer and decay in BioAVs. Probability distributions of modal KE anisotropy unveil flow asymmetries in the stenotic and one BioAV cases. Moreover, an inverse correlation between temporally averaged modal KE anisotropy and normalised instantaneous helicity intensity is noted, with the coefficient of determination varying among the valve configurations. Leaflet dynamics analysis highlights a stronger correlation between flow and biomechanical KE anisotropy in one BioAV due to higher leaflet displacement magnitude. These findings emphasise the role of valve architecture in aortic turbulence as well as its importance for BioAV performance and energy-based design enhancement.

Is there a role for cardiovascular magnetic resonance imaging in the assessment of biological aortic valves?

Patients with biological aortic valves (following either surgical aortic valve replacement [SAVR] or trans catheter aortic valve implantation [TAVI]) require lifelong follow-up with an imaging modality to assess prosthetic valve function and dysfunction. Echocardiography is currently the first-line imaging modality to assess biological aortic valves. In this review, we discuss the potential role of cardiac magnetic resonance imaging (CMR) as an additional imaging modality in situations of inconclusive or equivocal echocardiography. Planimetry of the prosthetic orifice can theoretically be measured, as well as the effective orifice area, with potential limitations, such as CMR valve-related artefacts and calcifications in degenerated prostheses. The true benefit of CMR is its ability to accurately quantify aortic regurgitation (paravalvular and intra-valvular) with a direct and reproducible method independent of regurgitant jet morphology to accurately assess reverse remodelling and non-invasively detect focal and interstitial diffuse myocardial fibrosis. Following SAVR or TAVI for aortic stenosis, interstitial diffuse fibrosis can regress, accompanied by structural and functional improvement that CMR can accurately assess.