When the Aortic Annulus Is Small, Does TAVR Valve Type Matter?

By Jeffrey Zimmet, MD, PhD, Associate Professor of Medicine, University of California, San Francisco; Director, Cardiac Catheterization Laboratory, San Francisco VA Medical Center

SYNOPSIS: In this propensity-matched analysis of transcatheter aortic valve replacement (TAVR) registry patients with small aortic annuli, the hemodynamic advantage of self-expanding TAVR valves was not associated with better clinical outcomes compared with balloon-expandable valves up to five years.

SOURCE: Okuno T, Tomii D, Heg D, et al. 5-year outcomes with self-expanding vs. balloon-expandable transcatheter aortic valve replacement in patients with small annuli. JACC Cardiovasc Interv 2023;16:429-440.

The two most commonly used transcatheter aortic valve replacement (TAVR) valve platforms feature different designs. The balloon-expandable Sapien valve includes a low profile with intra-annular valve leaflets. The self-expanding CoreValve platform, by virtue of its supra-annular construction, typically results in a larger effective orifice area and lower transvalvular gradients. In patients with small aortic annuli, would the hemodynamic improvements of the self-expanding valve lead to improved long-term clinical outcomes?

Okuno et al examined data from the Bern TAVI (Transcatheter Aortic Valve Implantation) registry and the Swiss TAVI registry. To this end, consecutive patients with an aortic valve annulus area less than 430 mm² were included for outcomes analysis. Between January 2012 and June 2021, 723 patients met the inclusion criteria. Among these, 389 patients were treated with a self-expanding valve (SEV) and 334 were treated with a balloon-expandable valve (BEV).

Before propensity score matching, patients treated with the SEV were older (83.1 years vs. 81.7 years; P = 0.003), were more likely to be female, and were living with more advanced heart failure symptoms. They also recorded smaller average aortic valve areas and exhibited smaller aortic root dimensions as measured by CT scan. After propensity score matching, investigators were left with 171 matched pairs for their analysis.

Overall, the technical procedural success rate was high and did not differ between the groups. As predicted, the authors wrote that based on prior analyses of SEV vs. BEV, those patients who received SEV recorded a lower mean transvalvular gradient (8 mmHg vs. 12.5 mmHg; P < 0.001) and a larger effective orifice area (1.81 cm² vs 1.49 cm²; P < 0.001). Patient-prosthesis mismatch was correspondingly higher among patients receiving BEVs.

In terms of clinical outcomes, all-cause and cardiovascular mortality were not significantly different between groups at five years (mortality rate of 50.4% vs. 39.6%; P = 0.269). In line with prior reports, the need for new permanent pacemaker implantation was significantly higher among patients who received a SEV (20.6% vs. 8.3%; HR, 2.68; P = 0.002). Paravalvular leak that was more than moderate was rare in each group, but any degree of paravalvular regurgitation was more frequently seen in patients with SEV. Repeat aortic valve intervention was numerically higher among SEV patients (2.1% vs. 1.2%), but this did not meet statistical significance. Importantly, rates of structural valve deterioration also were not significantly different between groups at the five-year mark (1.6% vs. 3.2%; 95% CI, 0.08-2.51; P = 0.367).

The incidence rate of any stroke reported in study patients was higher than in most series and was not significantly different between groups (12.3% vs. 7.2%; P = 0.114). However, disabling stroke occurred more frequently in SEV patients compared with BEV patients (6.6% vs. 0.6%; P = 0.03). This observation regarding severe stroke also was seen in the sensitivity analysis performed in the Swiss TAVI registry (5.3% vs. 2%).

The authors concluded using SEVs in patients with small annuli was associated with an improvement in hemodynamic parameters compared with BEVs, but this did not translate to better clinical outcomes with follow-up out to five years.

COMMENTARY

Patient-prosthesis mismatch (PPM) is a condition that occurs after AVR when the size or flow capacity of the implanted valve is too small relative to the patient’s body size or cardiac output. This can lead to restricted blood flow and increased pressure within the heart, which can result in worse patient outcomes.

In the TAVR literature, severe PPM has been associated with worse three-year mortality rates in patients with small aortic annuli, as the authors of the FRANCE-TAVI registry reported.¹ Empirically, one might expect the hemodynamic advantages of self-expanding TAVR valves would lead to improved clinical outcomes within five years.

Instead, Okuno et al reported no apparent benefit in terms of absolute clinical outcomes. Why might this be? An analysis of the other clinical parameters may give some insight. For example, the higher rates of permanent pacing and of paravalvular leak might offset any survival advantage of lower transvalvular gradients.

For now, these data suggest we should not be concerned much about the valve type for patients with small annuli who require TAVR. However, this is far from the last word. For example, recent advances in SEV deployment (e.g., cusp overlap technique to reduce pacemaker rate) and SEV construction (e.g., pericardial skirt present on the most recent iteration of these valves to reduce paravalvular leak) may make these observations less relevant in the TAVR realm going forward.

Another important aspect to consider is the population of patients undergoing TAVR now compared with 10 years ago — specifically, the strong trend toward treating younger and less sick patients with this technique as time passes. The average age of patients treated in the current trial was 82 years, and the overall mortality rate at five years approached 50%. It certainly is plausible that the hemodynamic advantages of SEVs in small annulus patients may be more evident over a longer period. Ultimately, this question will be answered by randomized trials. The creators of the SMART trial have reportedly completed enrollment, and results are expected in 2024.²

REFERENCES

1. Van Belle E, Vincent F, Labreuche J, et al. Balloon-expandable versus self-expanding transcatheter aortic valve replacement: A propensity-matched comparison from the FRANCE-TAVI Registry. Circulation 2020;141:243-259.

2. ClinicalTrials.gov. SMall Annuli Randomized To Evolut or SAPIEN Trial (SMART). Last update posted Dec. 12, 2022.