Registry Data Rekindle Talk Over the Best Valve for TAVI in Small Annuli

Debates over which transcatheter valves work best in small aortic annuli are being rekindled by new observational data—like the SMART trial before it, the IMPPACT TAVR registry shows no mortality difference between balloon-expandable and self-expanding devices a few years after treatment.

Initially, hemodynamic measures in the 26-center international registry were better with self-expanding valves, but by 3 years, this difference did not lead to a survival advantage, Henning Guthoff, MD (University Hospital Cologne, Germany), and colleagues report. Their findings are described in a research letter recently published in JACC: Cardiovascular Interventions.

In the SMART randomized trial of patients with small annuli and symptomatic severe aortic stenosis, both 1-year and 2-year data indicated less bioprosthetic valve dysfunction when using self-expanding valves. Thus far, though, no superiority over balloon-expandable valves for hard outcomes has emerged.

“Our results are basically consistent with what we already know from SMART,” said Victor Mauri, MD (University Hospital Cologne), senior author of the new study. In short, even before SMART, it’s long been known that echocardiography-derived gradients are lower with self-expanding valves, he noted. “This is not new.”

What their study adds, Mauri told TCTMD, is a larger cohort and a real-world perspective.

“In my opinion, the main question [is]: do these probable differences in hemodynamics actually impact patient outcomes? So far this has not been shown in any study,” he said. Longer follow-up from SMART may eventually reveal an advantage, but only time will tell, added Mauri. “To be honest, I doubt that there will be any difference, because SMART is not powered for hard clinical outcomes—it’s powered to show the superiority of hemodynamics. I don’t know whether this really translates into clinical outcomes, especially in this patient cohort of 80-year-old TAVR patients with a high background mortality and very many competing risks of death.”

Most patients we can probably treat with either valve without any problem. Victor Mauri

Howard C. Herrmann, MD (Perelman School of Medicine at the University of Pennsylvania, Philadelphia), a principal investigator for SMART, said the main message of these registry data is that “all of the [contemporary] valves that they looked at worked well at 3 years.”

The findings need to be confirmed in a prospective randomized study, both because of the brief format inherent to a research letter and the possibility of unmeasured confounders in an observational study, he said. Only a quarter of patients got balloon-expandable valves, “which is a relatively low number, certainly for the US,” Herrmann pointed out to TCTMD.

He asked: “Why were self-expanding valves chosen so often in this population?” The answer could relate to patient or anatomic characteristics, physician bias or experience, or valve availability at the hospital, and not all of these variables could be accounted for in the propensity adjustment, he said.

Other concerns, Herrmann added, include that the analysis grouped various self-expanding valves together despite these devices being quite different from each other. Also, the study was based on echocardiography done at discharge rather than 30 days and did not involve long enough follow-up to decisively show any divergence in clinical events between the two options.

IMPPACT TAVR

IMPPACT TAVR researchers analyzed data on 5,817 patients with an aortic annulus area ≤ 430 mm² who were undergoing TAVI for severe aortic stenosis with either balloon-expandable valves (Edwards Lifesciences’ Sapien XT, Sapien 3, or Sapien 3 Ultra) or self-expanding valves (Medtronic’s CoreValve, Evolut R, Evolut PRO, or Evolut PRO+; Boston Scientific’s Acurate neo or Acurate neo2). Nearly three-quarters received self-expanding valves.  

Patients in the balloon-expandable group, compared with the self-expanding group, tended to be younger (mean age 79.9 vs 81.9 years; P < 0.001), were more often men (21.8% vs 18.0%; P = 0.001), and had lower STS scores (mean 5.3% vs 5.4%; P < 0.001). Most comorbidities were evenly distributed, though patients treated with a balloon-expandable device were less apt to have atrial fibrillation/flutter (27.1% vs 31.5%; P = 0.001).

At baseline, mean transvalvular pressure gradient (ΔPmean) was slightly higher in the balloon-expandable group (44.6 vs 43.4 mm Hg; P= 0.009), as was mean LVEF (57.9% vs 58.7%; P = 0.033).

By the time of hospital discharge, echocardiography showed higher mean gradients and greater prevalence of severe patient-prosthesis mismatch (PPM) for patients who received a balloon-expandable versus self-expanding valve. However, moderate or greater paravalvular leak (PVL) was more common with self-expanding valves.

Echocardiographic Measures at Discharge by Valve Type

Despite these early differences, Kaplan-Meier analysis did not point to an imbalance in all-cause mortality at 3 years (23.0% with balloon-expandable vs 24.0% with self-expanding; log-rank P = 0.778).

The researchers performed multivariable Cox analyses that adjusted for age, sex, glomerular filtration rate, LVEF, and atrial fibrillation/flutter, again finding no survival benefit for either valve by 3-year follow-up. Nor were there any differences between the various self-expanding platforms.

“Mortality after TAVR appeared to be driven primarily by baseline comorbidities,” Guthoff and colleagues write. “Although lower gradients and less PPM may be particularly relevant for younger, more active patients, the higher incidence of PVL with self-expanding valves could have similarly important implications for long-term outcomes. Procedural complexity, conduction disturbances, and coronary access further contribute to the overall risk-benefit profile of each valve type.”

For now, without a consensus on how much hemodynamics fuel future outcomes, “it is important to look at each patient individually and not focus solely on hemodynamics” when choosing among valve types, said Mauri. In his own practice, he leans toward self-expanding valves in patients with small annular dimensions if there are no additional reasons to choose another valve. Coronary access, lifetime management, need for permanent pacemaker, and other factors each influence mortality to a small degree, he said, but the main predictors continue to be kidney function, LVEF, and male sex.

“But most patients we can probably treat with either valve without any problem,” Mauri added.

He said a clearer answer would likely come from a large trial powered to detect differences in hard events over a longer time span, but such a trial is unlikely given the expense of that undertaking and the diversity of patient characteristics.

When all other things are relatively equal, why wouldn’t you want the better hemodynamic valve? Howard C. Herrmann

Herrmann, for his part, believes that better hemodynamics will translate to significantly better hard outcomes—likely around 5 years. “Do I expect to see it at 2 or 3 years? The answer is no,” he commented.

Five-year data on Evolut R and CoreValve support this idea, as do the Evolut Low Risk trial, meta-analyses, and results from the National Echocardiography Database of Australia, Herrmann said. “These things take time. It takes years.”

Even at 2 years, SMART has started to pick up on some differences—in TIA and subclinical leaflet thrombosis, for example. “So we’re starting to see some early hints of differences between devices, but for those to compete out other causes of mortality in 81-year-olds is going to take more than 2 years,” Herrmann said.

Still, he and Mauri agree on the point that hemodynamics are only one factor. “I don’t think any decision should be made purely on hemodynamics,” Herrmann said, “but I think when all other things are relatively equal, why wouldn’t you want the better hemodynamic valve?”