Native aortic valve regurgitation and transcatheter aortic valve replacement: a word of caution or still too early?

Among some different meanings, a pantheon is “a small group of people or things that are considered to be the most important ones of their type” [1]. Another meaning contemplated by the Cambridge Dictionary, too, is “all the gods in a particular belief system, considered as a group” [1]. The situation is then that transcatheter aortic valve implantation (TAVI), which has revolutionized our views, feelings, diagnosis, and treatment of, initially and specifically, degenerative calcific aortic valve stenosis in the inoperable elderly patient [2], has become the first-line option in the treatment of aortic valve disease. Over time, physicians have extended the reach of this therapy, already 20 years old [3], to a diversity of patient cohorts considered at different types of risk and are now approaching a diversity of pathologies and anatomies such as pure native aortic valve regurgitation [4, 5].

Before proceeding, just a reminder that the acronyms TAVI and Transcatheter Aortic Valve Replacement (TAVR) are globally and indistinctly used when addresing this transcatheter therapy, being the latter more popular in North America with TAVI gaining more prominence across Europe. In India, it seems that both acronyms are equally used as one can deduct from searching in our Journal website, 50 articles with the acronym TAVI and 33 for TAVR [6]. Of interest is to notice that TAVR is mostly used for billing purposes across specific healthcare systems.

In the November 2023 issue of the Indian Journal of Thoracic and Cardiovascular Surgery, Narayan [7] discusses the PANTHEON (Performance of Currently Available traNscaTHEter Aortic Valve Platforms in Inoperable Patients With Pure Aortic regurgitatiON of a native valve) study [8] in which authors assess the feasibility and efficacy of TAVI with newer devices in patients with native aortic valve regurgitation. Good is that the PANTHEON study was an investigator-initiated international registry, initially avoiding the intrinsic bias of any study supported by the industry, regardless of design and budget. On the other hand, the strenghts and limitations of the study are clearly highlighted by Narayan [7].

Although among its strengths the sample size stands out as it represents one of the largest cohorts of patients with severe native aortic valve regurgitation treated using currently available transcather heart valves [7], it is appropriate to dig a bit more into the data produced by the authors of the PANTHEON. First, the patients included were implanted between May 2014 and September 2022, namely 8 years, and these implants were performed in 16 centers across Europe and the USA. The study cohort was 201 patients which means 1.6 patient/center/year. This is what it is, being the largest of such cohorts. Of course only 201 patients as the implanters selected these patients out of 15,000 due to the well-known challenges associated with TAVI implants in aortic regurgitation.

The overall technical success was 83.6% and device success 76.1% at 1 month, farther low when compared to regular implants for aortic stenosis. The combinaton of device migration and embolization reached 12.4%. More interesting though was a 22.3% rate of permanent pacemaker requirements, significantly high for current standards. And major bleeding, acute kidney injury >2 (AKIN criteria) and a second valve (more money) rates were in the range of 10%. Surgical conversion was 16% and procedure abortion 16%, too. Furthermore, authors lost 10% of their patients for follow-up at 1 year when we have been instructed for decades that for an appropriate follow-up assessment at any postoperative period should lie within the minimum of 95%. If the completeness of follow-up is 90% only in the first year, this raises some concerns about the intrinsic quality of the follow-up itself. And, remember, 16 centers collected 201 patients in an 8-year recruitment period.

The authors of the PANTHEON concluded that despite improved platforms and techniques, TAVR for pure severe aortic regurgitation remains a challenging procedure, with significant risk for migration and embolization [8]. The commentary by Narayan is a timely and objective one as he lets the data to speak for itself [7]. It is clear that the proponents will tell us that just a small proportion of the valves implanted were the Trilogy Valve (JenaValve, Irvine, CA, USA) and that we have to wait for more experience to be added. The recently published North American study [9] with a very small cohort of 27 patients showed an initial 81% procedural success in the first 5 patients, improving in the recent cases, a 13% new pacemaker rate and 7.4% surgical conversion rate. The ALIGN-AR Trial presented a few weeks ago at the 2023 Transcatheter Cardiovascular Therapy meeting [10], which enrolled 180 patients, seems to produce improved results.

The Narayan commentary has definitely highlighted the major current issues in this challenging field of transcatheter therapeutics for aortic regurgitation [7]. In any case we should not forget that balancing decisions and indications are the essence of surgery [11] and that the controversy between innovators and laggards will always be active as the show must go on.

Funding

None.

Declarations

Ethics approval

This study did not require Ethics Committee/Institutional review Board approval as it did not represent human research.

Informed consent

Not applicable.

Conflict of interest

The author declares that he has no conflict of interest in this study.

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