Impact of aortic landing zone geometry on TAVI implantation depth: comparison between ACURATE neo2 and Portico/Evolut
•,,,,,,,,,,,.
...
Abstract
Background During transcatheter aortic valve implantation (TAVI), increased aortic angulation can affect the final implantation depth of self-expandable (SE) devices due to the interaction between the high stent frame and the targeted aortic landing zone (LZ). We herein sought to investigate the behaviour of the ACURATE neo2, a SE device with a unique release mechanism, in relation to patient-specific angulation and curvature of the aortic LZ.
Methods The mismatch between the intended and the final implantation depth (∆H) was compared between patients treated with ACURATE neo2 (Acurate, n=106) and Evolut/Portico (n=101) SE devices. To do so, curvature (κLZ,tot) and angulation (αLZ,Dist) were calculated based on the three-dimensional aortic LZ centerline available from pre-TAVI CT.
Results The Acurate and Evolut/Portico groups showed a negligible difference (p=0.09) for ∆H averaged between non-coronary (NCC) and left coronary cusp (LCC). However, when splitting both ∆HNCC and ∆HLCC values into two subgroups based on κLZ,tot and αLZ,Dist median values, ∆H significantly increased on LCC compared with NCC in Evolut/Portico patients with high LZ curvature (κLZ,tot >0.123/mm, p=0.016) and high LZ distal angulation (αLZ,Dist >28.5°, p=0.012). No statistically significant differences arose within the Acurate group.
Conclusions Among SE devices, the ACURATE neo2 was the least affected by the curvature and angulation of the LZ anatomy, leading to a more predictable and symmetrical implantation depth. The clinical impact of this finding on TAVI outcomes in patients with an angulated aortic LZ warrants further investigation in larger studies.
What is already known on this topic
During transcatheter aortic valve implantation (TAVI), increased aortic angulation at the targeted landing zone (LZ) can influence the final implantation depth of self-expandable (SE) devices.
What this study adds
The study examined the impact of the patient-specific aortic LZ on the final implantation depth of ACURATE neo2. Among SE devices, ACURATE neo2 showed the least sensitivity to LZ anatomy, achieving a symmetrical depth closely matching the intended target on full release, even in patients with an angulated aortic LZ.
How this study might affect research, practice or policy
The ACURATE neo2 unique release mechanism enables a more predictable, symmetrical implantation depth during TAVI. This may help reduce postprocedural permanent pacemaker implantation and paravalvular leakage, warranting further investigation in patients with angulated aortic LZ.
Introduction
Transcatheter aortic valve implantation (TAVI) has become the preferred treatment for patients with severe aortic stenosis across different surgical risk levels.1–3 Greater aortic angulation, commonly referred to as a horizontal aorta, is recognised as an anatomical factor that can complicate TAVI procedures. Some studies suggest it may also impact procedural success, although the evidence remains inconclusive.4–8 We have recently reported that the interaction between the transcatheter heart valve (THV) and the aorta, namely the angulation of the aortic landing zone (LZ), may affect the final position of self-expandable (SE) Portico (Abbott, Minneapolis, Minnesota, USA) and Evolut-R/Pro+ (Medtronic, Minneapolis, Minnesota, USA) devices, which have a high stent frame, as compared with balloon-expandable (BE) Sapien 3 (Edwards Lifesciences, Irvine, California, USA) and Myval (Meril Life Sciences Pvt, Vapi, Gujarat, India) devices with a short stent frame.9
ACURATE neo2 (Boston Scientific, Marlborough, Massachusetts, USA) is a SE device with a high stent frame around 50 mm comparable to that of Evolut-R/Pro+ and Portico, but the THV frame is complemented by top-down deployment and stabilisation arches.10 Phase 1 of valve release consists of the opening of the upper crown and stabilisation arches which facilitate coaxial alignment between the THV and aortic root (AR) as well as the capping of the aortic leaflets. During phase 2, the distal part of the stent crown is released, providing valve anchoring to aortic leaflets to prevent asymmetric THV sliding in the left ventricle. However, the performance of this device according to the anatomy of the aortic LZ has been poorly explored.11
Hence, we herein sought to investigate the impact of angulation and curvature of the aortic LZ on the final implantation depth of ACURATE neo2, as compared with both Portico and Evolut-R/Pro+ SE devices.
Methods
This study originated from a retrospective, single-centre registry enrolling consecutive patients with severe aortic stenosis, available preoperative CT scan and measurements of implantation depth treated up to March 2023 at IRCCS Policlinico San Donato (San Donato Milanese, Italy). The study protocol was approved by the local ethics committee of IRCCS Ospedale San Raffaele (protocol code ‘AI4TAVI’, No. 33/INT/2023, approved on 15 March 2023) and conducted in accordance with the principles of the Declaration of Helsinki. Due to the retrospective nature of the study and use of anonymised data, informed consent was waived.
Data analysis
Data were retrieved from TAVI recipients treated between December 2016 and September 2021 with one of the following THVs: Evolut-R/Pro+ (Medtronic, Minneapolis, Minnesota, USA), Portico (Abbott, Minneapolis, Minnesota, USA), ACURATE neo2TM (Boston Scientific, Marlborough, Massachusetts, USA). Patients were excluded in case of valve-in-valve TAVI or bicuspid aortic valve. Patients were subsequently divided into two groups based on the implanted THV: (i) ACURATE neo2 (Acurate) and (ii) Portico or Evolut-R/Pro+ (Portico/Evolut).
A comprehensive description of the methods used in this study has been published and is freely accessible in our previous work.9 Briefly, the following procedure was employed (figure 1):
Pipeline of landing zone (LZ) analysis based on aortic centerline extracted from pre-TAVI CT imaging (A,B), intraprocedural evaluation of the implantation depth (C) and extraction of geometric features from the aortic LZ centerline (D). LCC, left coronary cusp; NCC, non-coronary cusp; TAVI, transcatheter aortic valve implantation.
Pre-TAVI imaging
CT angiography was acquired on a 256-row multidetector scanner (Siemens Healthineers, Erlangen, Germany), and optimal systolic reconstruction (BestSyst) was considered from ECG-gated image sequential acquisition.
Image post-processing
A trained operator imported and postprocessed each dataset in 3mensio Structural Heart (V.8.2, Pie Medical Imaging BV, Maastricht, The Netherlands) to extract three-dimensional aortic centerline. This process involved verifying the automatically generated centerline through multiplanar reconstruction views and adjusting the position of the centerline control points as needed. Both positions of the annulus plane (PAnn) and sinotubular junction (PSTJ), which delimit the AR unit, were annotated along the centerline. Aortic angulation, defined as the angle between the horizontal plane and the annulus,6 was measured on CT angiography using the implantation projection in which the three coronary cusps were aligned.
LZ analysis
A purposely-defined code written in Matlab (The MathWorks, Natick, Massachusetts, USA) was used to extract LZ geometric features from its centerline, as detailed in figure 1. Accordingly, each LZ length was determined based on the nominal height of the corresponding implanted THV and taking its label size into account: 50÷53 mm for Portico, 45÷46 mm for Evolut-R/Pro+ and 50 mm for ACURATE THVs. For all the THVs, a theoretical implant depth of 4 mm was assumed; further details available in theonline supplemental material 1 .
Procedure endpoint
The mismatch (∆H) between the intended (HPre) and the final (HPost) implantation depth (∆H = HPost– HPre) was calculated for each THV. The implantation depth was defined by averaging the maximal distance (expressed in millimetres) between the intraventricular end of the bioprosthesis and the aortic annulus at the level of both the non-coronary cusp (NCC) and the left coronary cusp (LCC). This measurement was extracted from the implantation projection where the inflow edges are aligned.12 The choice of implantation projection was left to the operator's discretion, allowing the use of either the three-cusps or cusp overlap views, guided by projection angulations predicted from CT angiography using 3mensio. Since 2019, the cusp overlap view has been more commonly employed. ∆H was computed at both cusps, yielding ∆HNCC and ∆HLCC, which were finally averaged to obtain the mean value ∆Hmean. The intended implantation depth was measured with the valve opened up to the non-recapture point for Portico/Evolut and with the valve capping the aortic leaflets and opened stabilisation arches for Acurate, prior to complete release. Also, device success after TAVI was defined according to the Valve Academic Research Consortium 3 (VARC-3) definition.13
Statistical analysis
The normality of data distribution was assessed using the Kolmogorov-Smirnov and Shapiro-Wilk tests. Continuous variables with a normal distribution are presented as mean±SD, while those not following a normal distribution are reported as median and IQR. Variables with a normal distribution were compared using the unpaired student’s t-test, whereas the Mann-Whitney U test was applied for skewed distributions. Categorical and dichotomous variables are expressed as counts and percentages and were compared using Pearson’s χ2 or Fisher’s exact tests, as appropriate. All p values were two-sided, with values <0.05 considered statistically significant. Statistical analyses were conducted using SPSS V.28.0 (IBM Italia, Milano, Italy).
Results
The study population included 106 patients treated with ACURATE, 22 with Evolut Pro+, 53 with Evolut-R and 26 with Portico THVs.
Baseline characteristics and LZ features
Baseline characteristics, including echocardiographic and CT-based measurements, are summarised in table 1. Patients in the Acurate group were older (p=0.003) and females were more represented (p<0.001). Differences between the two groups were not statistically significant in terms of most cardiovascular risk factors, specifically Society of Thoracic Surgeons score, creatinine clearance and aortic valve calcium score. Regarding echocardiographic features, the Acurate group showed higher left ventricle ejection fraction (p=0.04); on CT angiography, Acurate patients also reported greater aortic angulation (p<0.001) than Portico/Evolut patients as well as smaller diameters of aortic annulus (p<0.001), left ventricle outflow trunk (p=0.02) and sinuses of Valsalva (p<0.001) diameters. Focusing on LZ-specific baseline features (figure 2), the Acurate group showed a significantly higher κLZ,tot compared with the Portico/Evolut group (p=0.008), with median values equal to 0.137/mm and 0.123/mm, respectively. Additionally, αLZ,Dist was also significantly higher in the Acurate group (p<0.001), with a median value of 40.0° compared with 28.5° in the Portico/Evolut group.
Box and whisker plots of (A) κLZ,tot and (B) αLZ,Dist distributions along the aortic LZ centerline. Box and whisker plots of ∆H values clustered within the Acurate and the Portico/Evolut groups according to the median value of (C) κLZ,tot and (D) αLZ,Dist, respectively. LZ, landing zone; LCC, left coronary cusp; NCC, non-coronary cusp.
Table 1
•
Baseline patient characteristics
Further comparison between the Portico and Evolut subgroups revealed that, based on baseline anatomical characteristics (online supplemental material 1), the Portico platform was preferred over Evolut for patients with smaller aortic dimensions. Notably, there were no significant differences between the Portico and Evolut THVs in terms of baseline curvature (kLZ,tot) or angulations (αLZ,Proximal and αLZ,Distal).
Procedural data and in-hospital outcome
Procedural data and in-hospital outcome are detailed in table 2. Transfemoral access was used in the majority of patients (93.7%), while the subclavian access route was more frequent in the Portico/Evolut group (p=0.001), which also reported lower rates of predilatation (p<0.001) with respect to the Acurate group. Negligible differences were detected between the two groups in terms of vascular complications and stenting of the access site; of note, PCI with stenting during TAVI was more frequent in the Portico/Evolut group (p=0.03).
Table 2
•
Procedural and in-hospital outcome
Overall device success was satisfying and equal to 94.7%; though without reaching statistical significance, it was higher for Accurate than Portico/Evolut group (96.2% vs 93.1%). Permanent pacemaker implantation (PPI) was more frequent in the Portico/Evolut group (p=0.004); post-TAVI mean gradient, though statistically different (p<0.001) between the two groups, reported median values of 9.0 mm Hg and 7.0 mm Hg in the Acurate and Portico/Evolut groups, respectively.
Ejection fraction remained higher in the Acurate group (p=0.02), as already noticed at baseline. Rate of at least moderate paravalvular leak (PVL>moderate) remained comparable among the two groups (p=0.09), although it was higher in the Portico/Evolut group with a percentage rate of 6.9% against 1.9% in the Acurate group.
Implantation depth
The Acurate and Portico/Evolut groups showed a negligible difference in terms of ∆Hmean, when averaged across both aortic cusps (p=0.09). When examining individual cusps, ∆HNCC was significantly higher in the Acurate group compared with Portico/Evolut (p=0.009), while ∆HLCC remained comparable between the two groups. Differences were statistically negligible also when comparing ∆H values between NCC and LCC cusps within the same group (p=0.20 for Acurate and p=0.12 for Portico/Evolut). The Evolut platform reported a deeper intended implantation depth (HPre) at the LCC level compared with the Portico platform with median values of 7.0 mm and 5.0 mm, respectively (p=0.003 at posthoc analysis,).
When splitting both ∆HNCC and ∆HLCC values into two subgroups according to the median value of κLZ,tot (figure 2C) and αLZ,Dist (figure 2D), differences arose between ∆HNCC and ∆HLCC in the Portico/Evolut group only. Indeed, ∆H significantly increased on the LCC cusp compared with the NCC one in Portico/Evolut patients associated with high LZ curvature (κLZ,tot above 0.123/mm median value, p=0.016) and high LZ distal angulation (αLZ,Dist above 28.5° median value, p=0.012).
Specifically, as shown by the Bland-Altman analysis of the differences between ∆HLCC and ∆HNCC (), the Acurate group exhibited a consistent bias of −0.6 mm with comparable limits of agreement, regardless of both LZ curvature (κLZ,tot) and distal angulation (αLZ,Dist). Conversely, in the Portico/Evolut group, the bias markedly changed from −0.3 mm in patients with low κLZ,tot (and low αLZ,Dist) to 1.2 mm in patients with high κLZ,tot (and high αLZ,Dist).
Discussion
The main finding of the present study is that ACURATE neo2, despite being a high-frame SE valve, is less sensitive to the curvature and angulation of the LZ anatomy compared with Portico/Evolut THVs. This results in a symmetrical implantation depth, closely matching the intended depth on complete release, even in patients with an angulated aortic LZ. Indeed, when aortic LZ curvature and angulation increase, Portico/Evolut THVs exhibited significant sliding of the distal valve frame on LCC on complete release, due to the interaction between the upper part of the THV and ascending aorta.
Historically, the so-called horizontal aorta, defined by an aortic angulation ≥48◦, has been associated with lower rates of device success with SE as compared with BE valves,5 7 whereas other groups demonstrated no significant differences.8 14
In a previous study, we investigated additional factors that may explain the discrepancies observed in the literature.9 We found that the geometry of the entire aortic LZ, including both the AR and the proximal portion of the ascending aorta during SE valve implantation, progressively interacts with the THV during release and ultimately affects its final position, particularly when the LZ centerline has significant curvature and angulation. Indeed, our previous analysis demonstrated that increased angulation of the distal THV portion of the LZ significantly affects the final release of the device, resulting in a mismatch, i.e., ∆H, between the actual and intended implantation depth. Specifically, the final implantation depth of SE devices like Evolut-R, Evolut Pro+ and Portico tends to be deeper than intended, particularly on LCC due to the interaction between the high THV frame and the inner wall of the aortic lumen, especially during the final THV release.
In the context of horizontal aorta, the first iteration of the ACURATE neo THV demonstrated higher device success compared with Evolut R/Pro+,5 although it was also associated with a higher rate of moderate or greater PVL.15 Recently, in patients with horizontal aorta, ACURATE neo2 has been associated with a lower incidence of moderate or greater PVL compared with its predecessor, while maintaining comparable procedural success.11
To the best of our knowledge, this is the first attempt to evaluate the behaviour of the Acurate neo2 in relation to patient-specific geometrical features of the aortic LZ. According to our data, the ACURATE neo2 exhibited a comparable and symmetrical implantation depth between NCC and LCC, regardless of the LZ curvature and angulation; in contrast, significant ∆H differences were observed between NCC and LCC with other self-expanding valves, such as Evolut-R, Evolut Pro+ and Portico.
Our findings can be attributed to the synergistic action of the stabilisation arches and the top-down release mechanism of the ACURATE neo2 during phase 1, as illustrated in figure 3. We can hypothesise that the conformability of the stabilisation arches to the shape of the ascending aorta helps maintain the coaxial alignment between the THV and the AR during the capping of aortic leaflets by the upper crown. Similarly, the top-down release mechanism allows the operator to evaluate pre-emptively, before complete release, the potential impact of ascending aorta geometry on THV position. For instance, if coaxiality is lost at the end of phase 1, further advancement of the delivery system is required to realign the THV; this can be performed safely with the ACURATE neo2, without the risk of the THV sliding into the left ventricle thanks to the capping of aortic leaflets by the upper crown.
Mechanism of aortic landing zone interaction with ACURATE neo2 valve. (A–D) Initial positioning of the device with the black marker on the nadir of NCC. Due to the high curvature of the landing zone, the aortic root is not coaxial to the delivery system, leading to asymmetric implantation depth (red arrows). (B–E) During phase 1, the upper stent crown caps the aortic leaflets, and the stabilisation arches are gradually opened. The conformability of stabilisation arches to the curvature of the ascending aorta helps to improve the coaxiality of the whole system during the capping of aortic leaflets; implantation depth gets more symmetrical (yellow arrows). (C–F) During phase 2, the distal part of the stent frame is quickly opened. The valve is free from the tension of the delivery system and achieves its final position in the aortic root, maintaining a symmetrical implantation depth on both NCC and LCC. LCC, left coronary cusp; NCC, non-coronary cusp.
The clinical significance of our findings may be relevant in terms of reduction of postprocedural PPI and PVL, both of which have a prognostic impact.15–17 In this context, the symmetrical implantation depth observed in our analysis for the ACURATE neo2 may explain both the low single-digit PPI rate and the lack of correlation between increased aortic angulation and at least moderate PVL, as reported for ACURATE neo2 in the ITAL-neo registry.11
Finally, as the number of younger and low-risk patients undergoing TAVI will steadily increase in the future,3 18–20 the need for PPI and the occurrence of PVL will become less and less acceptable. Therefore, enhanced understanding of the strengths and weaknesses of each TAVI system applied in different cohorts of patients is crucial to improve procedural outcomes.
Limitations
The present study has several limitations that need to be taken into consideration.
First, this is a single-centre retrospective study with a relatively small sample size, and therefore possible bias in the selected population could be presumed. Significant differences in baseline characteristics, for example, age, gender and some CT-based features, were noticed between the Acurate and Portico/Evolut groups, with the former also showing a greater median value of aortic LZ angulation and curvature. Nonetheless, these less favourable baseline conditions in the Acurate group did not significantly affect THV implantation depth, thus further supporting the strength of our comparative analysis.
Second, the purpose of this study is purely hypothesis-generating. Larger, prospective studies are needed to determine whether symmetric versus asymmetric THV implantation in patients with angulated LZ anatomies will result in higher rates of PPI and PVL.
Third, the calculation of angulation and curvature of the aortic LZ centerline should be automated, for example, by incorporating these metrics into dedicated automatic workflows21 and made readily accessible to clinicians during routine TAVI planning.
Fourth, the Portico and Evolut platforms were grouped together due to their shared SE design, similar cell-based stent frame and bottom-up deployment mechanism. However, key differences remain, most notably in delivery system flexibility: Portico’s FlexNav uses a single-spine design allowing multidirectional flexion, while Evolut’s Enveo system employs a dual-spine structure limiting flexion to two directions. Also, the Portico stent is slightly longer (further details available in the). Therefore, a subanalysis of baseline and procedural characteristics stratifying the study population also by Portico and Evolut platforms is available in the .
Conclusion
The final position of ACURATE neo2 is not affected by the angulation and curvature of the device LZ anatomy, leading in all cases to a symmetrical implantation depth between NCC and LCC, as compared with Evolut-R, Evolut Pro+ and Portico THVs, which showed significant sliding on LCC on complete release in the presence of an angulated LZ.
Contributors: Contributors (guarantor: FS, corresponding author). RG and FS conceived and designed the work. OAO and FP contributed to the study design and to the collection data. JZ, EP and MS contributed to data collection and database integrity. EV supported in-house data processing; FS performed the statistical analysis. NB, EV and LT contributed to the analysis of the results. RG, FP and FS wrote the first draft of the manuscript; EV, JZ, OAO, MS and MT wrote sections of the manuscript and contributed to the critical revision of the intellectual content. OAO made the drawing of figure 4. LT, NB and FB contributed to the clinical interpretation of the results; FB contributed to funding acquisition. All the authors contributed to the revision of the final version of the manuscript and read and approved the submitted version.
Funding: This study was funded by the Italian Ministry of Health (Ricerca Corrente).
Competing interests: FB is a proctor for Medtronic, Abbott and Boston Scientific; NB and LT are proctors for Abbott and Boston Scientific. All the remaining authors declare no competing interests.
Provenance and peer review: Not commissioned; externally peer reviewed.
Supplemental material: This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.
Data availability statement
Data are available upon reasonable request. The data that support the findings of this study will be available from the corresponding author upon reasonable request.
Ethics statements
Patient consent for publication:
Not applicable.
Ethics approval:
This study involves human participants. The study protocol was approved by the local ethics committee of IRCCS Ospedale San Raffaele (protocol code 'AI4TAVI', No. 33/INT/2023, approved on 15 March 2023). Due to the retrospective nature of the study and use of anonymised data, informed consent was waived.
Acknowledgements
This study was partially supported by Ricerca Corrente funding from the Italian Ministry of Health to IRCCS Policlinico San Donato.
Mack MJ, Leon MB, Smith CR, et al. 5-year outcomes of transcatheter aortic valve replacement or surgical aortic valve replacement for high surgical risk patients with aortic stenosis (PARTNER 1): a randomised controlled trial. Lancet2015; 385:2477–84.
Popma JJ, Deeb GM, Yakubov SJ, et al. Transcatheter Aortic-Valve Replacement with a Self-Expanding Valve in Low-Risk Patients. N Engl J Med2019; 380:1706–15.
Gallo F, Gallone G, Kim W-K, et al. Horizontal Aorta in Transcatheter Self-Expanding Valves: Insights From the HORSE International Multicentre Registry. Circ Cardiovasc Interv2021; 14.
Gorla R, De Marco F, Garatti A, et al. Impact of aortic angle on transcatheter aortic valve implantation outcome with Evolut-R, Portico, and Acurate-NEO. Catheter Cardiovasc Interv2021; 97:E135–45.
Abramowitz Y, Maeno Y, Chakravarty T, et al. Aortic Angulation Attenuates Procedural Success Following Self-Expandable But Not Balloon-Expandable TAVR. JACC Cardiovasc Imaging2016; 9:964–72.
Medranda GA, Musallam A, Zhang C, et al. The Impact of Aortic Angulation on Contemporary Transcatheter Aortic Valve Replacement Outcomes. JACC Cardiovasc Interv2021; 14:1209–15.
Barki M, Ielasi A, Buono A, et al. Transcatheter aortic valve replacement with the self-expanding ACURATE Neo2 in patients with horizontal aorta: Insights from the ITAL-neo registry. Int J Cardiol2023; 389:131236.
Petronio AS, Sinning J-M, Van Mieghem N, et al. Optimal Implantation Depth and Adherence to Guidelines on Permanent Pacing to Improve the Results of Transcatheter Aortic Valve Replacement With the Medtronic CoreValve System: The CoreValve Prospective, International, Post-Market ADVANCE-II Study. JACC Cardiovasc Interv2015; 8:837–46.
Di Stefano D, Colombo A, Mangieri A, et al. Impact of horizontal aorta on procedural and clinical outcomes in second-generation transcatheter aortic valve implantation. EuroIntervention2019; 15:e749–56.
Pagnesi M, Kim W-K, Baggio S, et al. Incidence, Predictors, and Prognostic Impact of New Permanent Pacemaker Implantation After TAVR With Self-Expanding Valves. JACC Cardiovasc Interv2023; 16:2004–17.
van Wely M, Rooijakkers M, Stens N, et al. Paravalvular regurgitation after transcatheter aortic valve replacement: incidence, quantification, and prognostic impact. Eur Heart J Imaging Methods Pract2024; 2.
Prosperi-Porta G, Nguyen V, Willner N, et al. Association of Age and Sex With Use of Transcatheter Aortic Valve Replacement in France. J Am Coll Cardiol2023; 82:1889–902.
Gad MM, Elgendy IY, Saad AM, et al. Outcomes of Transcatheter Versus Surgical Aortic Valve Replacement in Patients <60 Years of Age. Cardiovasc Revasc Med2022; 43:7–12.
Mack MJ, Leon MB, Thourani VH, et al. Transcatheter Aortic-Valve Replacement with a Balloon-Expandable Valve in Low-Risk Patients. N Engl J Med2019; 380:1695–705.
Saitta S, Sturla F, Gorla R, et al. A CT-based deep learning system for automatic assessment of aortic root morphology for TAVI planning. Comput Biol Med2023; 163:107147.
