PARTNER Subanalysis Examines Effect of Annulus Size on Valve Hemodynamics, Outcomes

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Aortic annulus size influences valve hemodynamics and clinical outcomes after both transcatheter aortic valve replacement (TAVR) and surgical aortic valve replacement (SAVR), according to a subanalysis of the PARTNER trial published online September 30, 2014, ahead of print in Circulation: Cardiovascular Interventions.

“This study highlights the importance of considering aortic annulus size in the evaluation of high-risk patients who are candidates for aortic valve replacement,” Josep Rodés-Cabau, MD, of the Quebec Heart and Lung Institute (Quebec City, Canada), and colleagues write.

Methods
For the subanalysis, researchers divided high-risk patients from Cohort A of the randomized PARTNER trial (n = 574) and the study’s continued access registry (n = 1,358) into tertiles according to aortic annulus size:
  • Small: < 18 mm
  • Medium: ≥ 18 mm to < 20 mm
  • Large: ≥ 20 mm
 


RCT: Less Mismatch With TAVR vs SAVR

In the randomized cohort, patients with a small annulus had a higher 30-day rate of stroke with TAVR compared with SAVR (6.3% vs 0; P = .02) as well as more major vascular complications (18.4% vs 7.2%; P = .03). Also, surgery was associated with at least a trend toward more major bleeding irrespective of aortic annulus size (P = .02 for small and medium, P = .07 for large). Yet, 2-year mortality was similar for TAVR and surgery (P > .10 for all aortic annulus sizes).

Compared with surgery patients, TAVR patients had a lower incidence of severe patient-prosthesis mismatch (effective orifice area < 0.65 cm2/m2; 19.7% vs 37.5%; P = .03) and a trend toward an increase in moderate-to-severe paravalvular leak (5.7% vs 0; P = .06).

Among patients with a large aortic annulus, there was no difference in mismatch between treatment groups, although TAVR led to more paravalvular leak (9% vs 0; P = .01). Among patients with small annuli, meanwhile, TAVR was associated with less severe mismatch than surgery (P = .03). Also, paravalvular leak of any degree was lower in patients with small annuli (28.4%) than those with medium (45.8%) and large (53.1%) annuli (P < .001).

Registry: Larger Annulus Increases Mortality Risk

In the registry cohort, incidence of cerebrovascular events, major bleeding, and major vascular complications was similar regardless of annulus size. However, 1-year mortality was higher in those with larger annuli (24.8%) compared with patients with annuli that were medium (18.7%) or small (18.3%; P = .02). Moreover, a large annulus independently predicted death at 1 year, even after adjustment for baseline differences, and the presence of both mismatch and paravalvular leak compared with medium (HR 1.33; 95% CI 1.01-1.78) and small annuli (HR 1.37; 95% CI 1.02-1.85).

Valve hemodynamics were similar in this cohort regardless of annulus size—there was no difference in the rate of moderate-to-severe mismatch between those with small and large annuli (42.5% vs 40.4%; P = .57). Most patients (65%) with small annuli demonstrated no or trace paravalvular leak (P < .001 vs large) and the incidence of moderate-to-severe paravalvular leak was lower with small than with large annuli (5.9% vs 11.5%; P = .009).

Limitations of Retrospective Data

In a telephone interview with TCTMD, Dr. Rodés-Cabau noted several differences in TAVR practice between the time PARTNER was conducted and today. Namely, he said, “the vast majority of centers are [now] using 3D computed tomography to size the valves” and larger valve sizes were unavailable.

“This is why I think the results from the larger aortic annulus group should be interpreted with caution,” Dr. Rodés-Cabau continued. “However, regarding the small aortic annulus group, their results seem to be consistent with prior studies showing once again that the hemodynamics that you can obtain with these valves are quite good. For this particular group of patients, TAVR can be a very good option.”

Jonathon Leipsic, MD, of St. Paul’s Hospital (Vancouver, Canada), told TCTMD in a telephone interview that “stratifying [patients] based on annulus size is certainly a thoughtful idea…. I think this is a metric that was previously ignored, but it may help explain disparate outcomes.”

Citing the outdated nature of the PARTNER data, he commented that “the outcomes for patients with larger annuli, I suspect, would be significantly better now than historically.”

Evolution in Technique Affects Results

But currently, Dr. Leipsic said, annulus size should not play an extensive role in determining if a patient should receive TAVR or not. “There would have to be a randomized, prospective trial to actually look at that, and I'm not sure that it would because there are a number of other potential things that would come into play,” he said, noting that both the evolving technology and the changing baseline risk of potential candidates “will impact appropriate treatment.”

Future studies will also need to compare TAVR with surgery in the context of “special techniques like aortic enlargement and newer-generation devices in the surgical field,” Dr. Rodés-Cabau observed.

Note: Several study co-authors are faculty members of the Cardiovascular Research Foundation, which owns and operates TCTMD.


Source:
Rodés-Cabau J, Pibarot P, Suri RM, et al. Impact of aortic annulus size on valve hemodynamics and clinical outcomes after transcatheter and surgical aortic valve replacement: insights from the PARTNER trial. Circ Cardiovasc Interv. 2014;Epub ahead of print.

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Disclosures
  • The PARTNER trial was funded by Edwards Lifesciences.
  • Dr. Rodés-Cabau reports serving as a consultant to Edwards Lifesciences and St. Jude Medical.
  • Dr. Leipsic reports that his institution provides core lab and imaging services for Edwards Lifesciences.

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