When the Aortic Annulus Is Small, Does TAVR Valve Type Matter?
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.
This is a summarized version of the full in-depth article on Relias Media.
By Jeffrey Zimmet, MD, PhD, Associate Professor of Medicine, University of California, San Francisco; Director, Cardiac Catheterization Laboratory, San Francisco VA Medical Center
Transcatheter aortic valve replacement (TAVR) is an established procedure for patients with aortic stenosis, especially those at high surgical risk. Two major valve platforms are commonly used for TAVR: the self-expanding valve (SEV) and the balloon-expandable valve (BEV). These platforms differ in design and hemodynamic performance, particularly in patients with small aortic annuli. SEVs generally provide larger effective orifice areas and lower transvalvular gradients compared to BEVs. However, whether these hemodynamic advantages lead to better long-term clinical outcomes has remained unclear.
Study Overview: Data from the Bern and Swiss TAVI Registries
Okuno et al conducted a study using data from the Bern and Swiss TAVI registries to explore whether the hemodynamic improvements associated with SEVs in patients with small aortic annuli (area < 430 mm²) would translate to superior clinical outcomes. The study included 723 patients treated between January 2012 and June 2021. Among these, 389 received an SEV and 334 received a BEV. Key demographic differences between the two groups were adjusted through propensity score matching, resulting in 171 matched pairs for final analysis.
Hemodynamic Outcomes
As expected, patients treated with SEVs demonstrated superior hemodynamic performance. The mean transvalvular gradient was significantly lower in the SEV group compared to the BEV group (8 mmHg vs. 12.5 mmHg, P < 0.001). Similarly, SEV recipients had a larger effective orifice area (1.81 cm² vs. 1.49 cm², P < 0.001). Consequently, patient-prosthesis mismatch (PPM) was more common in the BEV group. These findings confirm the predicted hemodynamic advantages of SEVs in patients with small aortic annuli.
Clinical Outcomes: Mortality and Stroke Rates
Despite these hemodynamic improvements, the study found no significant difference in all-cause or cardiovascular mortality between SEV and BEV recipients at five years (50.4% vs. 39.6%, P = 0.269). Additionally, the incidence of stroke was higher than in most series but did not differ significantly between groups (12.3% for SEVs vs. 7.2% for BEVs, P = 0.114). However, disabling stroke was notably more frequent in SEV recipients (6.6% vs. 0.6%, P = 0.03), an observation supported by the sensitivity analysis performed on the Swiss TAVI registry data.
Procedural Complications and Pacemaker Implantation
The need for new permanent pacemaker implantation was substantially higher in the SEV group (20.6% vs. 8.3%, HR 2.68, P = 0.002). This is a known drawback of SEVs, which can interfere with the heart's conduction system, leading to a greater requirement for pacemakers. Paravalvular regurgitation was also more frequent in the SEV group, although cases of moderate or severe regurgitation were rare in both groups.
Structural Valve Deterioration and Repeat Interventions
Rates of structural valve deterioration were low and did not differ significantly between groups (1.6% vs. 3.2%, P = 0.367). Similarly, repeat aortic valve intervention was numerically higher in the SEV group (2.1% vs. 1.2%), but this difference was not statistically significant. These findings indicate that long-term valve durability is comparable between SEV and BEV platforms in this patient population.
Commentary on Patient-Prosthesis Mismatch and Future Directions
PPM is a critical concern in aortic valve replacement, particularly in patients with small aortic annuli. Severe PPM has been associated with worse outcomes, including increased mortality. Given that SEVs offer better hemodynamic performance, it might be expected that they would reduce PPM-related complications and improve survival. However, this study's results suggest that the hemodynamic advantages of SEVs do not translate into better clinical outcomes over five years.
Several factors may explain this discrepancy. Higher rates of pacemaker implantation and paravalvular regurgitation in SEV patients could negate any potential survival benefit from lower transvalvular gradients. Moreover, the population undergoing TAVR has evolved over the years, with younger and healthier patients increasingly being treated. The current study cohort had an average age of 82 years, and nearly half of the patients had died by the five-year follow-up. It is possible that the benefits of SEVs may become more apparent in younger, lower-risk populations over longer follow-up periods.
Summary
This study demonstrates that while SEVs provide superior hemodynamic outcomes compared to BEVs in patients with small aortic annuli, these improvements do not result in better clinical outcomes over a five-year period. The increased risk of pacemaker implantation and disabling stroke with SEVs may offset their hemodynamic advantages. However, ongoing advancements in SEV technology, such as newer deployment techniques and improved valve designs, may change this outlook in the future. Results from upcoming randomized trials, such as the SMART trial, will provide further clarity on the optimal valve platform for these patients.
Read the full in-depth article on Relias Media
We discuss self-expanding and balloon-expandable valves in more detail in our full write-up on Relias Media.