Performance of a new generation of transcatheter aortic valves

Elkoumy, Ahmed Ibrahim Abdalla Mohamed
Degenerative (calcific) Aortic Stenosis (AS) is a common valvular heart disease among the elderly in Western countries and is expected to become more prevalent worldwide with an ageing population. Transcatheter aortic valve implantation (TAVI) has emerged and been approved as an alternative to surgical aortic valve replacement with the advantage of safety and efficacy in all surgical risks. Since the TAVI has been implemented in patients using either balloon-expandable valve (BEV) or self expandable valve (SEV), frequent complications were detected with further investigations and scrutiny of the devices, with a proven impact on patient's survival and quality of life, like moderate or more paravalvular leakage (PVL), major vascular complications, associated bleeding, and permanent pacemaker implantation (PPMI). Therefore, the manufacturers have to improve the valves, delivery, and vascular access systems to tackle such complications. By either improvement of the devices or offering newly featured devices fitting with new indications. The objective of this thesis is to investigate the performance and outcomes associated with new TAVI devices introduced by new manufacturers, including either implantation in a challenging anatomical feature, or by using corrected or novel methods to assess the haemodynamic outcomes. In Chapter 2, the safety and efficacy of a newly introduced BEV in patients with severe bicuspid AV (BAV) stenosis from India and Europe were investigated. BAV is still considered an unfavourable anatomy for TAVI in guidelines, with the absence of strong enough evidence obtained from randomized controlled trials. The results showed that a relatively young patients with low surgical risk and different phenotypes of stenotic BAV were treated using the new BEV. Device technical success was achieved in 97% of patients. At 30-day device success was achieved in 93% and early safety was reported in 91% of patients. The rate of PPMI was 8%. Haemodynamic performance was acceptable, mean pressure gradient of 9.8mmHg, and a low incidence of moderate PVL (3%). Chapter 3 represents a 1-year follow-up of patients; with severe BAV stenosis (cohort in Chapter 2), who were previously treated with the new BEV valve. The follow-up included VARC-3 defined clinical and haemodynamic performance at 1-year. As a result, the median follow-up duration was 13 months with all-cause mortality of 11%, while cardiovascular mortality was 5%. Stroke was reported in 3% and PPMI was required in 8%. No patient required valve related surgery or reintervention. The device's haemodynamic performance appeared stable over the follow up duration with only one patient (2.1%) reported with severe (Stage III) haemodynamic deterioration. In Chapter 4 a new BEV with a new sizing matrix was implanted in three patients with anatomical obstacles that might limit the safety and efficacy of TAVI. The device is introduced with XL sizes (30.5 and 32mm) fitting with large annulus without the need for significant oversizing, In the three patients AV anatomical characteristics were challenging with severe valve calcifications, BAV, and very large annulus dimensions exceeding the limit of available other contemporary TAVI devices. Patients were treated successfully with 32mm devices, without procedural or in-hospital complications. 30-day follow-up revealed favourable outcomes, no death, or valve related reintervention. Haemodynamic performance was acceptable with trace PVL in the three patients. In chapter 5 a newly designed iteration of the previously mentioned BEV (chapters 2,3, and 5) was introduced with significant changes in the design of the valve design and new features were added to the delivery system aiming for better performance in terms of more reduction of PVL and PPMI through proposing the possibility of shallower implantation in addition to more controlled implantation guided by the added radio-opaque markers. The aim of this chapter was mainly the assessment of the residual PVL after implantation using a newly validated non invasive technology from the final aortogram in a quantitative form (Videodensitometry). 103 patients treated by TAVI using this device were retrospectively analysed and included patients with tricuspid (62%) and bicuspid AV (37%) with all phenotypes, with different degrees of valve calcification. the device is introduced with a new sizing matrix with only 1.5mm increment between devices instead of 3mm. the analysis of residual PVL using quantitative aortography revealed that 77.7% of patients were adjudicated with none/trace PVL, 20.4% with mild, and 1.9 with moderate PVL. In comparison to the first iteration, the new valve design showed a significant shift from mild to none/trace PVL. Inter observer variability (ICC = 0.92, 95% CI 0.78–0.97) and intra-observer variability (ICC = 0.97, 95% CI 0.93–0.99) showed excellent reproducibility of the analysis using the quantitative aortography technology. In Chapter 6, the reassessment of the aortic valve area (AVA) as one of the essential haemodynamic parameters after implantation of a new SEV in patients with severe AS was investigated, using a combined, multimodality imaging technique. This was based on the use of directly measured left ventricular outflow tract (LVOT) area from pre-TAVI MDCT scans to be combined with Doppler measurements obtained from the predischarge Echocardiography to recalculate the continuity equation. Aiming to reassess the calculated AVA using the conventional (based only on all measures obtained from TTE) and the combined method. Based on that reclassification of AVA in addition to the rate of prosthesis patient mismatch. The results showed that the LVOT area measured from MSCT was significantly larger than LVOT calculated from TTE measurement (405 vs 350mm2, [95% CrI -55.15, -36.09]), resulting in large AVA based on MSCT-LVOT in comparison to AVA based on TTE-LVOT (2.6 vs 2.3cm2 [95% CrI -0.85, -0.43]). The rate of patient prosthesis mismatch was significantly lower and reclassified from 8.5% to 2.3% when the MDCT-LVOT area was used to recalculate AVA and indexed AVA (cm2 /m2 ). intra- and Inter-observer reliability was excellent for LVOT area measured by MDCT (ICC = 0.99 [95% CI; 0.98–0.99]) and (ICC = 0.98 [95% CI; 0.95 to 0.99]), respectively and was good regarding TTE (ICC = 0.87 [95% CI; 0.71, 0.95]) and (ICC = 0.85 [95% CI; 0.63, 0.94]). In Chapter 7 the feasibility of omitting systematic balloon aortic valvuloplasty with a new SEV during the TAVI procedure was explored. Systematic valvuloplasty is highly recommended by the manufacturer, aiming for the achievement of higher technical success. We retrospectively investigated patients’ cohort treated using the valve to identify the rate of valvuloplasty omission, based on that identifying patients' characteristics and the early procedural and hospital outcomes. The results showed only 22% of patients treated directly with TAVI without balloon valvuloplasty. AV anatomical characteristics were different between the two cohort. Patient without valvuloplasty had a smaller AV annulus and lower calcium volumes, than patients received valvuloplasty (22.6 vs 23.4 mm; p<0.001) and (163 vs 581mm3 ; p<0.001) respectively. In the matched cohorts, VARC-3 device technical success was similar (95%) and all other outcome measures were statistically comparable between cohorts. The only noticeable differences were numerically lower rates of balloon post dilatation (19% vs 31%; p=0.08), PPMI (3.6% vs 7.1%, p=0.50), and numerically higher mild or more PVL (45% vs 35%, P=0.25) in the cohort treated without valvuloplasty. In Chapter 8 we explored the gaps, unmet needs, and new indications with the current TAVI practice and how these mandates further improvement of the currently available TAVI devices. The recently introduced TAVI devices whether as a new iteration of the available TAVI devices, in addition to devices still under investigation or development, were explored. This includes the recently developed BEV or SEV introduced by the known manufacturers or newly developed devices by new manufacturers. The main technical features of new devices were reported including both the valve design and the delivery systems. In addition to that summarizing the suspected impact of the new devices, on the device performance, associated outcomes, and optimization of the TAVI procedure. In conclusion, this thesis conducted a summary of the performance of two newly introduced TAVI devices. This performance included the feasibility and safety of implantation in challenging anatomy, BAV and large annulus, which represent an emerging indication, in addition to that correction of the haemodynamic analysis of the implanted devices based on the multimodality imaging approach, which might be helpful to eliminate the controversy and disagreement between different parameters during the follow-up or when malfunction is suspected. In this thesis a new imaging modality was used to assess PVL as one of the important haemodynamic parameters after implantation of a newly device TAVI implantation and showed favourable results, in addition to reproducibility of the analysis using this new technology. Additionally in this thesis a change in the practice using one of the new TAVI devices was proposed based on an observational analysis, which showed feasibility of the suggested changes in specific patients with specific characteristics, aiming to achieve a truly minimalistic approach using this device in comparison to the other contemporary devices. Finally, TAVI procedure and new TAVI devices are still progressing, more understanding is required. The continuous improvement of the currently available TAVI devices and introduction or development of other new devices is essential to optimize the procedure and outcomes. The future of the TAVI might be targeting the concept of “patient specific TAVI device selection” through selecting the valve according to each patient specific characteristics.
NUI Galway
Publisher DOI
Attribution-NonCommercial-NoDerivs 3.0 Ireland