Review Article

Patient-specific Factors Influencing Choice of Transcatheter Aortic Valve Prosthesis

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Abstract

Transcatheter aortic valve (TAV) implantation is an established treatment strategy for patients with severe aortic stenosis across the spectrum of surgical risk profiles. Numerous randomised controlled trials have consistently demonstrated the safety and efficacy of TAV implantation compared with surgical aortic valve replacement, prompting an expansion of indications towards lower surgical risk, often younger, patients. In parallel, the number and types of TAV prosthesis have also increased. Although all devices have generally demonstrated favourable procedural and longer-term clinical outcomes, variations in frame design, material properties and leaflet configurations render specific devices more favourable in certain settings. In this review, we describe key differences in TAV design and how this may affect the choice of TAV prosthesis in the challenging clinical scenarios of patients with small annuli, coronary disease, long life expectancy, risk of permanent pacing and aortic regurgitation, which are expected to be encountered more frequently as indications for TAV implantation expand.

Keywords

Transcatheter aortic valve implantation (TAVI), transcatheter aortic valve design, lifetime management, redo TAVI, coronary access, aortic regurgitation, small annulus,

Received:

Accepted:

Published online:

DOI: https://doi.org/10.15420/icr.2024.40

Disclosure: AAK has received consulting fees from Machnet Medical, honoraria from Boston Scientific and travel support from Boston Scientific and PCR congresses. JC has received a grant from Boston Scientific and travel support from Cardiovalve and Lara Lab, and participates on an advisory board for Medtronic. MA has received consulting fees from Abbott, Boston Scientific, Edwards Lifesciences, JenaValve Technology, Medtronic and Meril. All other authors have no conflicts of interest to declare.

Correspondence: Arif A Khokhar, The Heart Center – Rigshospitalet, Inge Lehmanns Vej 7, Copenhagen, Denmark. E: arifkhokhar@doctors.org.uk

Copyright:

© The Author(s). This work is open access and is licensed under CC-BY-NC 4.0. Users may copy, redistribute and make derivative works for non-commercial purposes, provided the original work is cited correctly.

Transcatheter aortic valve (TAV) implantation (TAVI) is an established treatment strategy for patients with severe aortic stenosis across the spectrum of surgical risk profiles.1 Numerous randomised controlled trials have consistently demonstrated the safety and efficacy of TAVI compared with surgical aortic valve replacement, which has prompted an expansion in indications towards lower surgical risk, often younger, patients.2–4

In parallel with this expansion, the number and types of transcatheter aortic valve (TAV) prostheses have also increased, with a range of different TAV designs now available commercially. Although all devices have generally demonstrated favourable procedural and longer-term clinical outcomes, variations in frame design, material properties and leaflet configurations render specific devices more favourable in certain settings.

In this review, we describe key differences in TAV design and how this may affect the choice of TAV prosthesis in the challenging clinical scenarios of patients with small annuli, coronary disease, long life expectancy, risk of permanent pacing and aortic regurgitation (AR), which are expected to be encountered more frequently as indications for TAVI expand.5,6

Transcatheter Heart Valve Prostheses

Current transcatheter heart valves (THVs) can be categorised by the mechanism of valve delivery (balloon versus self-expandable), height of the valve frame (tall versus short) and by the anatomical positioning of the valve leaflets relative to the aortic valve annulus (intra- versus supra-annular). Each of these categories, along with unique design features of the individual platforms, can lead to differences in feasibility, safety, haemodynamic and clinical outcomes.

Balloon-expandable valves (BEVs) are made from cobalt-chromium-based alloys akin to coronary stents. The most frequently used Sapien family (Sapien XT, Sapien 3, Sapien 3 Ultra, Sapien 3 Ultra Resilia; Edwards Lifesciences) and the more recently introduced Myval, Myval Octacor and Myval Octapro (Meril) consist of a short stent frame height, with an intra-annular position of the TAV leaflets and a top row of open cells. Newer generations of BEVs are being developed to enable commissural alignment to be performed, a key consideration for coronary re-access and redo TAV replacement (TAVR).7–9

In contrast, self-expanding valves (SEVs) consist of a nitinol-based tall metallic frame with distinct commissural posts from which the TAV leaflets are suspended. These leaflets can be either supra-annular (as is the case with the Evolut family of THVs [Medtronic], the Allegra [New Valve Systems] or Hydra [SMT] THVs) or positioned in an intra-annular position, as in the case of the Portico/Navitor (Abbott), a tall-frame SEV. The tall-frame design, although necessary to ensure even distribution of radial force, often leads to the outflow portion extending above and beyond the sinotubular junction (STJ), encapsulating the aortic root in a metallic cage-like structure, with open cells of varying sizes allowing blood circulation between the TAV prosthesis, aortic wall and neo-sinuses.10 The tall frame height, combined with the commissural posts and variable cell sizes, can pose additional challenges for coronary cannulation or redo-TAVR, as described later.

A large meta-analysis comparing BEVs and SEVs did not demonstrate a significant difference in all-cause mortality, bleeding or vascular complications at 1–2 years.11 BEVs were associated with a slightly higher risk of non-disabling stroke, but there was no difference between BEVs and SEVs in disabling stroke.11 SEVs are associated with a significantly increased risk of permanent pacemaker implantation (PPI) compared with BEVs, which is inherent to their self-expanding mechanism of deployment.12 However, among SEVs, this risk varies with different devices and can be modified using dedicated procedural techniques.12 Both SEVs and BEVs may behave differently in the presence of heavy dense calcification, with an SEV more likely to conform around heavy particularly nodular calcification, increasing the risk of paravalvular leak; in contrast, the balloon-expanding nature of BEVs may increase the risk of aortic annular or left ventricular outflow tract rupture. Haemodynamic parameters favour SEVs, with larger effective orifice areas and lower transvalvular gradients observed, particularly when the leaflets are in a supra-annular position.11 Durability data are excellent for both BEVs and SEVs out to 10 years, although severe structural valve deterioration does appear to be more common with BEVs.13

In summary, a wide range of THVs is available with excellent safety and efficacy data. However, there is mounting evidence that valve choice has a significant effect on the anatomical, haemodynamic and functional outcome of TAVI. Therefore, both patient and valve-specific factors need to be carefully considered to ensure the right valve is chosen for the right patient.

Approach to Patients With Small Annuli

Challenges of Small Annuli

To date, there is no clear consensus as to the anatomical parameters that constitute a small annulus. The current literature defines an annular diameter <23 mm, an aortic annulus area of ≤430 mm2 or a surgical bioprosthesis sized ≤23 mm as a ‘small annulus’.14–16 Of note, small annuli are predominantly found in women, compromising up to 80% of the population in certain series.17 The challenges arising for bioprostheses in patients with such small annuli mainly relate to the haemodynamic consequences of a smaller valve, observed as higher gradients and an increased risk of prosthesis–patient mismatch (PPM). Although for surgical bioprostheses the surrounding sewing ring further decreases the actual functional valve area, in the case of TAVI, especially in the case of intra-annular devices, with the stent frame present and the displaced native leaflets compressing its structure, valve function and subsequent haemodynamics may also be compromised. For surgical aortic valves, increased gradients and PPM (i.e. a too-small valve relative to the patient’s body size, defined as an indexed effective orifice area), have been directly linked with earlier valve degeneration and decreased survival.18,19 In addition, TAVI underexpansion, which can frequently occur in small annuli, can lead to leaflet pinwheeling, which impairs effective leaflet coaptation and has been proposed as a potential mechanism for early structural valve degeneration.20

In the era of TAVI in patients with small annuli, the entire surrounding aortic root anatomy needs to be considered because the interaction of narrow sinuses and the small dimensions of the STJ with potentially tall and prominent device frames may result in distinct challenges, such as impaired coronary access (CA) or sinus sequestration in the case of redo procedures.21

Performance of Different Transcatheter Aortic Valve Implantation Devices in Small Annuli

Given the challenges in patients with small annuli and the suggested differences in the performance of different TAVI devices in such anatomies, dedicated randomised trials comparing the available platforms have been conducted.

The Small Annuli Randomized To Evolut (SMART) randomised controlled trial (RCT) enrolled over 700 patients with an annulus area of ≤430 mm2, treating patients with either a BEV intra-annular device or an SEV supra-annular device. Although at 12 months there was no significant difference in the clinical endpoints of death, disabling stroke or heart failure (HF) hospitalisation, the coprimary endpoint testing bioprosthetic valve dysfunction demonstrated significant superiority of the SEV platform over the BEV platform (mean gradient: 7.7 versus 15.7, respectively; haemodynamic structural valve dysfunction: 3.5% versus 32.8%, respectively; moderate or severe PPM: 11.2 versus 35.3%, respectively).16 However, it is important to note that the endpoint of structural valve dysfunction was based on post-procedural echocardiography, the assessment of which is subject to variations in THV design and methods of evaluation.22 In addition, there is growing evidence highlighting the discordance in echocardiography-based versus invasive-derived haemodynamic gradients and their relative clinical significance.23 Therefore, further longer-term data are awaited to definitively confirm whether elevated post-procedural echocardiography-based gradients are associated with early degeneration and adverse clinical outcomes.

In the setting of valve-in-valve TAVI for a degenerated surgical bioprosthetic valve, the LYTEN trial randomised approximately 100 patients with a failed small surgical valve (defined as ≤23 mm) to receive either a BEV or a supra-annular SEV. At 30 days, there was clinical equipoise (no death or stroke events), but patients receiving a SEV had significantly better haemodynamics than those receiving a BEV (mean gradient: 15 versus 23 mmHg, respectively; PPM 44% versus 64%, respectively).15 At 1 year, these findings were confirmed with a significantly higher rate of intended valve performance (defined as a mean gradient <20 mmHg, peak velocity <3 m/s, Doppler velocity index ≥0.25 and less than moderate AR) in the SEV than BEV group (76% versus 30%, respectively).24

Device Choice in Small Annuli

The aforementioned issues, as well as data concerning the performance of different devices in small annuli, all need to be considered when selecting a specific TAVI device for a patient with a small anatomy. In particular, in younger patients with a longer life expectancy, a supra-annular device with the promise of superior haemodynamics may be the preferred choice. However, this needs to be balanced against the potential issues associated with tall-frame devices, such as challenging CA.21,25,26 In this regard, consideration should be given to the supra-annular SEV selected, because certain devices have larger cell sizes and can more reliably achieve commissural alignment, which further facilitates CA.27 In contrast, for elderly comorbid patients with a shorter life expectancy and when notable coronary artery disease is present, potentially requiring percutaneous coronary intervention (PCI) later on, a short-frame BEV device may be preferred.

Finally, when an intervention for severe aortic stenosis (AS) is considered in a young patient with long life expectancy and a small aortic root anatomy, which often coexists with a small annulus, a careful preprocedural assessment is mandatory to evaluate whether a potential redo procedure is feasible after TAVI. If challenges such as a high neoskirt or sinus sequestration can be foreseen, then SAVR with aortic root enlargement, to enable the implantation of an as-large-as-possible bioprosthesis, can be considered.

Approach to the Patient With Coronary Disease

Severe AS and coronary artery disease often coexist, and a growing body of evidence supports the safety of deferring coronary revascularisation to after TAVR.28–30 In addition, in younger patients, the lifetime cumulative risk of developing acute or chronic coronary syndrome after TAVR requiring subsequent intervention is increased.31–33 Together, these findings highlight the need to preserve CA, especially in younger patients undergoing TAVR.

CA following TAVR may be challenging or unfeasible for a not insignificant number of patients.21,34 Placing a TAV inside the aortic root creates additional barriers, which a coronary catheter must overcome in order to cannulate the coronary ostia.25 The combination of the TAV frames and/or leaflets and their geometric interaction with the surrounding aortic root anatomy dictates the challenge and feasibility of CA after TAVR. Therefore, TAV design can have a significant impact on the feasibility of CA.

All TAV prostheses have a sealing pericardial skirt, designed to reduce paravalvular regurgitation, which extends up from the inflow portion of the prosthesis. This sealing skirt represents an impenetrable barrier for a coronary catheter, and its height dictates the lowest point at which a catheter can traverse the valve frame. The overall height of the TAV frame dictates how far above the coronary ostia the metallic barrier extends. With a short-frame TAV, if the outflow is positioned below the level of the coronary arteries, then CA is unhindered. In contrast, for taller-frame TAV, the metallic valve frame extends above the coronary ostia and STJ, in which case CA is usually achieved by traversing the valve frame through the open cells. Although all contemporary TAV have cells of sufficient size to allow the passage of a 6-Fr coronary catheter, larger cell sizes allow for catheters to be more easily rotated and manipulated into position to achieve selective and supportive CA.21,25

The metallic frame acts as the scaffold for the TAV leaflets, which can either have an intra-annular or supra-annular position. The higher the position of the leaflets, the more likely they are to engage and interact with coronary catheters. Leaflet pinning or restriction in leaflet mobility can occur, particularly when using supportive or aggressively shaped catheters (e.g. Amplatz Left) with supra-annular TAV.35

TAV leaflets are attached to the valve frame at three commissural posts, which present an additional impenetrable barrier for catheters. Commissural misalignment of a TAV will result in one of the commissural posts landing directly opposite one or both coronary ostia, leading to challenging or unfeasible CA.26,27 Procedural techniques to achieve commissural alignment can partially mitigate the challenge posed by the commissural posts by ensuring that the origin of the coronary ostia arises between the two commissural posts.36–38

Together, these elements of TAV design can combine to affect how challenging, or even feasible, CA is. A tall-frame TAV with wide commissural posts, supra-annular leaflets and small cell size would be the most challenging scenario for CA. In the RE-ACCESS study, CA after different TAV was evaluated in 300 patients.21 Unsuccessful coronary cannulation was observed in 23 (7.7%) of the 300 patients, with 22 of the 23 instances of unfeasible CA arising with the tall-frame supra-annular Evolut TAV.

In addition to TAV design, the implantation technique can also affect CA. As alluded to earlier, ensuring optimal commissural alignment can facilitate CA.26,27 In the follow-up RE-ACCESS 2 study, the rate of unsuccessful CA dropped from 17.9% to 7.5% with the adoption of commissural alignment techniques for the Evolut TAV.27 However, current-generation TAVs vary in their ability to be reliably and consistently rotated to ensure optimal commissural alignment. In addition to alignment, TAV implantation depth can also affect CA.39,40 Although a high TAV implantation may be more favourable in terms of avoiding conduction disturbances, this raises the height of different elements of the TAV frame and/or leaflets in relation to the coronary ostia and STJ.

Therefore, when approaching a patient with significant coronary artery disease, or if post-TAVR revascularisation is expected, then consideration should be given to the TAV design and implantation technique. A short-frame BEV TAV may be preferable in this instance (Figure 1). If other factors dictate the use of a tall-frame SEV, then a specific tall-frame TAV with either larger cells (e.g. Navitor or Hydra) or the ability to be easily rotated to ensure commissural alignment should be used. The latest-generation Evolut FX+ has been modified to include three large cells at the level of the coronary ostia and, when combined with a dedicated technique to achieve commissural alignment, is more favourable for CA.41

Figure 1: Complex Percutaneous Coronary Intervention After Transcatheter Aortic Valve Implantation

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Approach to the Patient With Long Life Expectancy

As TAVR expands to younger populations with longer life expectancy, it is anticipated that patients may outlive the durability of their index implanted TAV.42 Strategies for treating degenerated TAV include redo TAVR or surgical explantation, with the latter associated with higher rates of periprocedural and longer-term morbidity and mortality.43,44 In contrast, redo TAVR compares favourably, with a growing body of evidence supporting the safety and efficacy of this approach.45–47 However, for a significant proportion of patients, a redo TAVR procedure is deemed unfeasible due to the risk of coronary obstruction. This risk is dictated by the geometry of the assembled redo TAVR complex with the surrounding aortic anatomy. Therefore, when treating patients with long life expectancy, consideration should be given to the choice of TAV and the implant technique used for the index TAVR, to ensure that a redo TAVR strategy is feasible in the long term.48

Feasibility of Redo TAVR

During redo TAVR the leaflets of the first degenerated TAV are pinned upright by the frame of the second TAV. As the leaflets of the first TAV are pinned back, a cylindrical barrier, similar to a covered stent, will be created. The height of this covered portion of leaflets is termed the leaflet neoskirt.49,50 If the height of the leaflet neoskirt of the assembled redo TAVR complex ends up above and in close approximation (2–4 mm gap) to the coronary ostia and STJ, then the risk of coronary obstruction and sinus sequestration, respectively, is high. It therefore follows that factors that influence neoskirt height, as well as anatomical factors, influence the feasibility of redo TAVR (Figures 2 and 3).

Figure 2: Redo transcatheter aortic valve implantation for a Degenerated Self-expandable Valve

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Figure 3: Clinical and Technical Considerations for Choosing a Transcatheter Heart Valve

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Impact of TAV Design

The type, combination and sequence of TAV can influence neoskirt height.10,49 A tall-frame valve with supra-annular leaflets has the potential for a greater neoskirt height if used as the index TAV than does a shorter-framed or intra-annular TAV. Redo TAVR with the use of two tall-frame TAVs would create the greatest leaflet neoskirt height, in contrast with redo TAVR with two short-frame THVs inside each other. Using a short-frame BEV to treat a degenerated tall-frame TAV has the advantage of being able to modulate neoskirt height based on the implantation depth of the second short-frame TAV.51,52 To date, there are limited data comparing different redo TAVR strategies. In the Redo-TAVR registry, 212 consecutive redo TAVI procedures were evaluated.46 A BEV-in-SEV approach was used in 56 of 212 (26%) procedures, whereas an SEV-in-BEV approach was used in 31 of 212 (15%) procedures.46 The overall 30-day mortality and procedural safety were similar regardless of whether the first or second THV was a BEV or SEV, but procedural success was higher if the second THV implanted was an SEV (77.2%) rather than a BEV (64.3%).53 This was driven by lower residual gradients when the second THV used was an SEV (median [interquartile range] 10.3 [8.9–11.7] versus 15.2 [13.2–17.1] mmHg, respectively).

Impact of Index TAV Implantation

In addition to TAV design, the implantation depth and commissural alignment of the index TAV deserve attention when considering the possibility of redo TAV in the future. In the contemporary era, there has been a systematic drive to achieve higher implantation depths in order to minimise PPM rates.40 However, a higher index TAV implant will result in a greater leaflet neoskirt height after redo TAVR, which increases the risk of coronary inaccessibility and/or coronary obstruction. This may be particularly relevant for patients with lower STJ and coronary heights, where a lower implantation of the index TAV may be preferred to preserve the possibility for future redo TAVR.

In the setting where redo TAVR is deemed potentially unfeasible due to a high neoskirt height, then adjunctive leaflet modification techniques may prove useful.54 In particular, if the index TAV is a tall-frame valve with supra-annular leaflets, then leaflet modification by creating a gap in the pinned-up leaflet neoskirt can ensure preservation of CA and/or coronary flow. However, in order for leaflet modification to be effective, commissural alignment of the index TAV is necessary.55 Therefore, if selecting a tall-frame TAV for the index procedure, then a valve type that facilitates reliable and consistent commissural alignment should be considered.

Approach to the Patient With High Permanent Pacing Risk

Conduction disease necessitating PPI is a common complication following TAVI, associated with an increased risk of all-cause mortality, HF hospitalisations and prolonged hospital stays.56

Accurately identifying patients with a high baseline pacing risk is the first step in successfully mitigating the chance of significant conduction disturbance after TAVI. Pre-existing conduction disease is a major risk factor for the need for PPI after TAVI, with baseline right bundle branch block the strongest predictor.57 Multivariate analyses have also demonstrated a wide range of baseline demographic and cardiovascular risk factors, including older age, male sex, hypertension, ischaemic heart disease, renal impairment and AF.58 Further delineation of high-risk phenotypes is possible from more detailed anatomical characterisation. The atrioventricular node is located in the triangle of Koch, whereas the atrioventricular bundle is found at the lower border of the membranous septum before entering the ventricular septum. A short membranous septum length, measured by CT, has been identified as an important anatomical risk factor for PPI after TAVI.59 In the INTERSECT-TAVI registry, a membranous septum length <3 mm was associated with a high risk of new PPI (>20%) relative to the risk of new PPI with a membranous septum length >7 mm (risk <10%). Furthermore, in a meta-analysis of 5,740 patients, a 1 mm decrease in the length of the membranous septum was associated with an OR of 1.6 (95% CI [1.28–1.99]) for new PPI after TAVI.60 Histology specimens exhibit substantial interindividual anatomical variation in atrioventricular bundle course, further delineating high- and low-risk phenotypes.61 However, current imaging techniques do not allow for this detail of anatomy-based risk stratification in clinical practice. Several studies have also shown that the distribution of aortic valve calcification predicts PPI risk.62,63

Choosing the Right Device

Device size is a simple but critical contributor to PPI rates after TAVI, with device oversizing having the biggest impact of all multivariates in a high-pacing-risk cohort treated with a BEV (OR 3.4; 95% CI [1.4–8.5]; p=0.008).64 It is therefore essential to avoid, when possible, significant oversizing in high-risk individuals. The type of THV and the mechanism of deployment also affect PPI rates. Contemporary trial data in low-surgical-risk cohorts show 30-day PPM rates of 17.4% and 6.5% for the Evolut SEV and Sapien BEV, respectively.3,4 In a large French registry of 50,000 all-comer TAVI patients (Sapien or Evolut R), the rate of PPI within 30 days of TAVI was 22.4%.58 Using early BEV models as the reference, there was an OR of 0.88 (95% CI [0.81–0.95]) for the latest BEV iterations and an OR of 1.17 (95% CI [1.07–1.27]) for the latest SEV.58

Procedural Considerations to Mitigate Risk

Several procedural factors can influence PPI rates and should be carefully considered, particularly in high-risk patients. Importantly, higher device implantation is associated with lower rates of PPI. Implantation depth is generally measured in millimetres from the base of the non-coronary cusp to the prosthesis stent inflow on the corresponding side, with specific individual targets described for the individual TAVI valve platforms. Additionally, a patient-tailored approach can be considered, taking into account the length of the membranous septum.65 Using cusp-overlap fluoroscopic projection may help optimise implantation depth and reduce PPI rates.12 Even among SEVs, using a dedicated implantation technique with the cusp-overlap approach has been shown to reduce PPI rates to below 10%, highlighting the importance of the implant technique.66 Recapturability of devices may become an increasingly valuable feature to help operators achieve the level of implant depth precision required. Optimising valve position to minimise PPI risk clearly needs to be balanced against several other factors, including the risk of paravalvular leak and valve embolisation.

It is important that heart teams recognise patients at high pacing risk, considering all relevant data, including baseline risk factors and demographics, pre-existing conduction disease and membranous septum length. These data must then be weighed against the wider clinical picture and treatment aims to inform decisions around device selection and procedural steps to reduce the risk of PPI after TAVI.

Approach to the Patient With Pure Aortic Regurgitation

Clinical Relevance of Aortic Regurgitation

Epidemiologically, AR appears to be at least as frequent as AS. In the OxValve study, 1.6% of the general population aged ≥65 years showed significant (moderate-to-severe or greater) AR, whereas calcific AS was present in only 0.7%.67 The Framingham cohort saw relevant AR in 2.2% of individuals aged ≥70 years, and in the recent Heart of New Ulm Valve study, 4.5% of individuals aged ≥65 years showed clinically significant (moderate or greater) AR.68,69 If AR is present at a severe stage with related symptoms of dyspnoea, then annual mortality reaches around 25%.70

Although the guidelines for the treatment of AS have seen marked changes over the past decade, driven by the success of TAVI and the continuum of positive data compared with surgical aortic valve replacement across all surgical risk groups, AR recommendations, in contrast, remained unchanged. Surgical therapy of AR is recommended in the case of relevant symptoms and a decrease in left ventricular ejection fraction to <50% or progressive left ventricular remodelling.1

Pure Aortic Regurgitation as the Next Frontier for Transcatheter Aortic Valve Implantation

During the early experience with TAVI, AR treatment was attempted as an off-label procedure, using conventional BEV and SEV devices.71,72 However, treating pure AR is often more technically challenging. The lack of leaflet calcification for device anchoring and significant enlargement of the aortic annulus and aortic root, combined with a hyperdynamic circulation during valve deployment, can all contribute to an increased risk of periprocedural complications. Recent data from the PANTHEON registry showed that after implantation of conventional TAVI prostheses in patients with pure AR, technical success was only approximately 80%, with embolisation or migration of the device occurring in 15% of patients and relevant residual AR present in approximately 10%.73 In addition, the lack of calcification exposes the THV frame to the conduction system, increasing the risk of PPI in these patients.

To overcome these limitations, dedicated devices have been developed, with the JenaValve Trilogy system (Edwards Lifesciences; formerly JenaValve) being the first CE-marked device (Figure 4). The unique feature of this SEV short-frame platform is the three dedicated locators that are placed in the nadir of each cusp from above the native valve after release of the system, ‘clipping’ it to the non-calcific leaflets. Data on the initial European experience with this new platform demonstrates 0% rates of embolisation and residual AR.74 However, high rates of new pacemaker implantation of approximately 20% after TAVI in AR remain a limitation, seen with conventional devices, but also with the new dedicated platforms, potentially driven by the lack of protective calcium between the device and the conduction system. In the ALIGN-AR trial, the initial US study of the JenaValve system, the implementation of a dedicated implantation regimen (less oversizing and higher implant position), the pacemaker rate could be reduced to 14%.75 However, it should be noted that currently available dedicated devices, such as the JenaValve, have a limited sizing range, which can be an issue when treating pure non-calcific AR, when often the annuli are large. In this context, off-label devices have to be used, aiming for at least >20% oversizing. In this respect, the Myval BEV has shown initial promise due to its ability to treat larger annulus sizes.76

In conclusion, in patients with severe pure AR, given that effective dedicated TAVI devices are becoming available, a transcatheter option should be carefully evaluated. Furthermore, awareness towards this frequent aortic disease entity is needed now that after several decades new, less invasive, treatment alternatives are available.

Figure 4: Transcatheter Aortic Valve Implantation for Patients With Pure Aortic Regurgitation

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Selection of Transcatheter Aortic Valve Prostheses

As TAVI continues to evolve into a safe, effective and reproducible procedure, it will be used for an ever-broader range of indications and population groups. With a plethora of different TAV devices now commercially available, the possibility emerges of adopting a more patient-specific tailored approach in choosing the TAV prosthesis. Multiple anatomical, clinical and procedural factors should be considered when selecting a particular TAV prosthesis. The first basic requirement of any TAV prosthesis is to ensure that an effective result can be achieved reliably and consistently with a good safety profile, minimising the rates of greater than mild paravalvular regurgitation and conduction disturbances. All current-generation devices are now expected to at least achieve this benchmark. However, beyond this, patient-specific factors will dictate which particular design features of specific TAV prostheses may be more favourable. In this context, determining the clinical priorities, both procedurally and longer term, for the patient being treated can be used to guide TAV selection. For example, for a patient with a previous permanent pacemaker system, the risk of conduction disturbances becomes irrelevant. In a younger patient with significant coronary artery disease that may require future coronary intervention, a short-frame TAV prosthesis may be preferred to facilitate future coronary re-access. The challenge arises in clinical scenarios where there are competing priorities, as often encountered in the setting of patients with small annuli, particularly those with small aortic roots. As described above, using a supra-annular SEV may offer more favourable haemodynamics, and therefore potentially enhanced durability, but using a tall-frame valve with supra-annular leaflets may compromise future coronary re-access and the potential feasibility for redo TAVR. In this setting, additional patient-specific technical and clinical factors may need to be considered, such as vascular access, aortic root and annular anatomy, degree of calcification, ventricular function and expected life expectancy. The integration of all these patient-specific factors can then be used to guide optimal TAV selection to ensure a successful procedural result both acutely and in the longer term.

Conclusion

A multiparametric approach combining the technical factors derived from preprocedural imaging and patient-specific clinical factors can be used to guide selection of the best TAV prosthesis to ensure optimal immediate and longer-term outcomes.

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