Supra-annular sizing of transcatheter aortic valve prostheses in raphe-type bicuspid aortic valve disease: the LIRA method☆
Introduction
Transcatheter aortic valve implantation (TAVI) is a valid option for the treatment of severe aortic stenosis as an alternative to surgical aortic valve replacement [1,2]. Latest evidences show that TAVI can be offered to patients with low surgical risk, therefore, shifting to a younger population [3]. In this cohort, the prevalence of bicuspid aortic valve (BAV) anatomy is higher [4,5]. However, a small proportion of patients with BAV anatomy may present the disease at advanced age. The prevalence of octogenrerians and nonagenerians in the BAV population varies from 4,5% to 28% [6]. In this specific subgroup of patients TAVI might be a valid option for the treatment of severe aortic stenosis due to a higher risk of surgical complications related to age, frailty, and other comorbidities. BAV anatomy is characterized by heavily calcified leaflets, commisural fusions, calcific or fibrotic raphes, slit-like elliptical orifices and it is also associated with a greater aortic angulation and ascending aorta dimensions compared with tricuspid aortic valve patients [7]. These anatomical aspects have raised the risk of suboptimal results in first-generation devices due to a high rate of paravalvular leak (PVL), device underexpansion, need for a second transcatheter heart valve (THV), aortic dissection and annular rupture [8]. Latest retrospective registries show that the device success rate has improved with the introduction of new-generation THVs [9,10]. However, a higher rate of procedural complications and clinical events is still maintained in the BAV cohort. A retrospective analysis of the Transcatheter Valve Therapy (TVT) registry that included only 3rd generation balloon-expandable Sapien 3 devices (Edwards Lifesciences, Irvine, California,USA) found a higher rate of 30-day of stroke, annular rupture and conversion to open surgery in the bicuspid vs tricuspid cohort [11]. A recent restrospective analysis from the same registry including both balloon and self-expandable devices (81% new generation devices with a majority of balloon-expandable THVs), confirms the improvement of device success and the reduction of moderate-severe aortic insufficiency with new-generation devices, leading to slightly inferior procedural results in bicuspid vs tricuspid TAVI procedures [12]. Particularly, current generation self-expanding prostheses were the minority of devices implanted in this registry analysis and they were associated with a three times higher incidence of post-procedural moderate-severe aortic insufficiency when compared with balloon-expandable prostheses. According to these results, TAVI might represent a valid alternative to cardiac surgery in BAV anatomy, where surgical aortic valve replacement (SAVR) is the reference treatment due to its optimal results and the exclusion of BAV anatomy from randomized clinical studies evaluating TAVI vs SAVR [[1], [2], [3],13]. However, procedural and device success in BAV anatomy still need to be improved with all types of THVs prostheses.
Appropriate prosthesis size selection is essential for a high device success in TAVI in order to optimize the interference between the prosthesis and the anatomy [14]. BAV represents a challenge for an adequate prosthesis sizing due to its anatomical peculiarities [8,9,15,16]. Particularly, the narrowest part of the aortic root in BAV anatomy seems across the aortic valve leaflets instead of the annular virtual basal ring (VBR) [17]. However, even if largely accepted, this concept has not been reproducibly demonstrated and specific measurements to assess the supra-annular level are not standardized across different operators.
A recent multicentre computed tomography (CT) scan study has identified a supra-annular plane that predicts THV prosthesis-anchoring in raphe-type BAV disease, named as LIRA (Level of Implantation at the RAphe) plane [18]. The main objective of our study is to evaluate the safety of a novel supra-annular sizing method to optimize prosthesis sizing in raphe-type BAV disease by performing sizing measurements at the LIRA plane (the LIRA sizing method).
Section snippets
Study design and population
The LIRA sizing method was applied to all consecutive patients treated with TAVI for aortic stenosis in raphe-type BAV disease between November 2018 to January 2020 using different types of THV prostheses. BAV was defined as a deformed aortic valve with 2 functional cusps forming a valve mechanism with <3 zones of parallel apposition. The LIRA sizing method was applied to BAV type 1 and 2 according to Sievers classification; type 1 identified valve morphologies with one raphe, and type 2 was
Baseline characteristics
Between November 2018 and January 2020, a total of 20 patients were included. Mean age was 81 ± 5.4 years, 70% were males with a median Society of Thoracic Surgeons (STS) predicted risk of mortality score of 4.3 (3.0–6.5). Baseline characteristics of the included cohort are reported in Table 2. CT scans identified three different BAV anatomies: 15 patients with type 1 BAV and calcific raphe, 2 patients with type 1 BAV and fibrotic raphe and 3 patients with type 2 BAV. VBR perimeter
Discussion
The main findings of our study are the following:
- 1)
THV prosthesis sizing according to the LIRA method appeared to be safe with a high device success in a cohort of 20 patients with raphe-type BAV disease;
- 2)
The application of the LIRA method might optimize THV prosthesis sizing in patients with raphe-type BAV disease;
- 3)
Tracing the internal borders of the leaflets to obtain the perimeter at the LIRA plane could predict the perimeter occupied by the prosthetic valve;
- 4)
Two commissures were visibles in <50%
Limitations
There are several limitations in our study. First, this was a single-centre non-randomized study. Second, TTE measurements were not performed by a core laboratory for the diagnosis of BAV and for the evaluation of echocardiographic outcomes.Third, our proposed sizing methodology (LIRA method) needs to be validated in a larger prospective multicentre registry.
Conclusions
Supra-annular sizing according to the LIRA method in raphe-type BAV patients seems safe with a high device success with different types of THV prostheses. Further larger studies are needed to confirm our preliminary findings.
Declaration of Competing Interest
Matteo Montorfano serves as proctor for Boston Scientific. The other authors have nothing to disclose.
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2021, Journal of BiomechanicsCitation Excerpt :Conceptually, this will vary from patient to patient depending to dimensions, morphology and calcium load of annulus and leaflets. This is in line with proposals to include supra-annular structures of the aortic root in addition to the dimensions of the annulus itself for sizing in patients with BAV (Iannopollo et al., 2020; Iannopollo et al., 2019; Petronio et al., 2020; Xiong et al., 2018). Acknowledging the small-scale observational nature of this study, we found that the valve frame mobilized the supra-annular structures to a lesser extent in BAV than in TAV patients.
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All authors take responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation.
- 1
Both authors contributed equally to this manuscript.