Author + information
- Marco Barbanti, MD∗ ()
- ↵∗Address for correspondence:
Dr. Marco Barbanti, Division of Cardiology, Ferrarotto Hospital, University of Catania, Via Citelli 1, Catania 95124, Italy.
One of the most distinguishing features of the modern era is the pace at which science offers us new devices and revolutionary technologies. Transcatheter aortic valve replacement (TAVR) does not escape this fact. Over the last 15 years, this technique has taken an incredible journey, characterized by an extraordinary growth of procedural expertise, device improvement, and increasing clinical evidence (1).
The very early-generation TAVR devices and techniques were anything but perfect. Prostheses and delivery catheters looked like the handmade tools of some mad scientist, and operators mainly relied on their exceptional interventional background and intuition to accomplish the procedure. This raised concerns regarding the safety and reproducibility of the procedure (1). In a short time, along with increased operator experience, our instruments have been extensively refined: valve design has approached that of surgical bioprostheses, and delivery systems have become less bulky and easier to handle, reducing the rate complications and allowing for a wider range of treatable patients (2). However, despite these advancements, some important limitations remain (i.e., vascular injury, stroke, suboptimal positioning, conduction disturbances, and paravalvular regurgitation) (2). Therefore, the aim of the last-generation TAVR devices is to address such limitations by further reducing delivery systems profile and incorporating additional key features for a more predictable deployment (2).
This issue of JACC: Cardiovascular Interventions offers the readers the results of the initial experience with the new repositionable Evolut R prosthesis (Medtronic, Minneapolis, Minnesota) from the UK & Ireland Implanters’ Registry (3) and the Evolut R U.S. Study (Medtronic CoreValve Evolut R United States IDE Clinical Study) (4). As compared with the previous generation CoreValve, the Evolut is designed to enable recapturability and repositionability. The prosthesis is tailored to reduce the overall height while preserving the height of the pericardial skirt with an extended skirt to provide a seal against paravalvular regurgitation. In addition, cell geometry has been redesigned in order to achieve optimized radial force. The Evolut R has also been designed to be implanted through a 14-F compatible delivery system, the EnVeo R, which integrates an InLine sheath (Medtronic). Finally, positioning accuracy is aided by the EnVeo R delivery system’s 1:1 torque response.
Both of these studies encompassed high-risk patient populations with severe aortic stenosis. Kalra et al. (3) reported a periprocedural success rate of 91.3% and a 30-day mortality rate of 2.3%. The rates of cerebrovascular accidents, major vascular complications, and pacemaker implantation were 3.8%, 5.3%, and 14.7%, respectively. Of note, moderate or severe paravalvular aortic regurgitation was observed in 7.7% of patients at 30 days.
The results of the Evolut R U.S. Study are in line with those reported by the UK & Ireland Implanter’s Registry: The all-cause 30-day mortality rate was 2.5%. Disabling stroke was uncommon (3.3%). The frequency of major vascular complications was 7.5% and a permanent pacemaker was placed in 16.4% of patients. Moderate residual paravalvular regurgitation was identified in 5.3% of cases (4).
Valve performance was excellent with very low residual aortic valve gradient (<9 mm Hg in both studies). These low gradients may have important implications for long-term clinical outcomes and for re-do TAVR procedures in case of late structural valve deterioration (5).
We have been using the Evolut R, but so far there are very few published data on the performances and the clinical outcomes of this new generation TAVR device. Therefore, these 2 studies represent a timely contribution to current published reports, although sample sizes are small (264 in the UK & Ireland Implanter’s Registry, 241 in the Evolut R U.S. Study) and length of follow-up is still short. The studies are simple, and the investigators did not carry out particularly sophisticated analyses. However, the results of these registries are not trivial and lend themselves to a number of important considerations.
In terms of vascular accesses, the vast majority of patients included in these studies (94% in the UK & Ireland Implanter’s Registry and 90% in the Evolut R U.S. Study) were treated using the transfemoral route. In a high-risk and old population including almost 25% and 35% of individuals with peripheral artery disease, this represents a tremendous success, also considering the very low rate of major vascular complications (5% and 7%). In this context, the lower profile and the higher traceability of the new delivery system have enabled treatment of patients with vessels as small as 5 mm with a greater burden of tortuosity and calcification, and may have the potential to minimize the risk of vascular complications.
Cerebrovascular events are the most devastating complication of TAVR. In the present studies, the risk of periprocedural stroke was 3.8% and 3.3%, which are well in line with comparable cohorts from recent registries using previous and new-generation devices (2). According to these early observations, the majority of new-generation TAVR devices did not seem to provide an incremental benefit in terms of stroke. Repetitive repositioning of recapturable self-expanding and mechanical expanding designs into the aortic root to obtain optimal valve implant may potentially have played a role in these findings, counterbalancing in some way the benefit of devices with enhanced traceability and lower profile. This is highly speculative and needs to be confirmed in properly designed studies.
Particular consideration must be made when analyzing the rates of pacemaker implantation and paravalvular regurgitation. It is undeniable that an ∼17% 30-day pacemaker implantation rate has rarely been reported with the previous generation CoreValve, and 7.7% and 5.3% of more than mild paravalvular regurgitation also represent a non-negligible step forward as compared with the CoreValve device. However, these results cannot be considered completely satisfying. This is particularly true in an era in which TAVR is being progressively offered to younger and lower-risk patients, and the paravalvular leak rate is approximately 1% to 2% with some new-generation transcatheter aortic valves (2). Therefore, operators, engineers, and industry still need to get together and provide even more new solutions to further improve these results.
I personally believe that the improvements reported up to now with the Evolut R are remarkable, but they are mostly the result of the improved release mechanism, which has facilitated achieving optimal implantation depth, rather than the valve itself. In my view, patient selection can be further refined. Popma et al. (4) found that the frequency of the residual paravalvular regurgitation was inversely related to the device-to-annular ratio, thus supporting the concept of an “aggressive” annular oversizing with self-expanding valves to achieve better outcomes. However, no doubt, there is still room for additional technological progress. Of course, this will need commitment, ability and courage to change, without being afraid to fail. In creating the electric light bulb, Thomas Edison carried out more than 1,200 experiments to find a filament that could become incandescent without burning; during this time, on being told it might be better to give up, he replied: “At least, today I've just learned how not to make a light bulb” (6).
This is exactly the spirit we should embody. We have already achieved exceptional outcomes, but this is not the time to rest on our laurels and enjoy our success. It is mandatory to keep working hard and united, and we will succeed in providing our patients the most reliable and efficient solution for their pathology.
↵∗ Editorials published in JACC: Cardiovascular Interventions reflect the views of the authors and do not necessarily represent the views of JACC: Cardiovascular Interventions or the American College of Cardiology.
Dr. Barbanti is a consultant for Edwards Lifesciences.
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