麻豆传媒

PHOENIX -- The Navitor transcatheter aortic valve replacement (TAVR, TAVI) device was associated with a high pacemaker implantation rate in its pivotal study, but an analysis showed ways to bring that rate down.

The 30-day new permanent pacemaker implantation rate was 19.0% in the high and extreme surgical risk population studied, Ibrahim Sultan, MD, of the University of Pittsburgh Medical Center, reported at the annual TVT conference hosted by the Cardiovascular Research Foundation.

He argued that this was in line with other self-expanding valves, like the 15% rate with the ACURATE neo2 device and 16.4% with the Evolut R device in similar risk populations.

However, those might not be fair comparisons, argued session discussant Michael Young, MD, of Dartmouth-Hitchcock Medical Center in Lebanon, New Hampshire. With the advent of using cusp overlap techniques, pacemaker rates have dropped for Evolut, for example, he noted.

"That was a different time," agreed Dharam J. Kumbhani, MD, SM, of the UT Southwestern Medical Center in Dallas. "If you're using the cusp overlay technique right now, you're getting sub 10% rates for pacemaking."

TAVR has gotten safer.

"The mortality data now in this contemporary era with TAVR, it's 1.5%, we're not in the 6-8% that were before," Kumbhani told 麻豆传媒. "So now the bar is actually very high. ... As we expand our armamentarium of valves, that I think you have to define your right population, especially in an era when the complications and safety are low and safety so high."

But TAVR will need to get even safer if the indications are to expand, said session panelist Philippe Pibarot, PhD, of the Quebec Heart and Lung Institute in Quebec City.

"I think the population that we're going to treat...will change dramatically in the future years, because eventually the indication of TAVI will expand to asymptomatic, severe, and maybe moderate risk AS [aortic stenosis]," he said. "This will raise the bar for TAVI, because you cannot afford, ideally, any degree of severe PVL [paravalvular leak], you don't want to have a pacemaker, and you want to have coronary access."

Sultan's group searched for predictors of lower complication risk in the Navitor approval study, which included 260 patients at 26 sites in the U.S., Europe, and Australia who got Navitor TAVR for severe, symptomatic aortic stenosis after being deemed high or extreme risk for surgical valve replacement.

In the single-arm study at 30 days, all-cause mortality and disabling stroke both occurred in 1.9% of patients, while there were no cases of moderate-to-severe paravalvular leak.

Predictors of the 19.0% rate of new permanent pacemaker implantation included pre-existing atrioventricular block and pre-existing right bundle branch block, as expected from prior data.

Among anatomical factors considered in the multivariable analysis as predictors of need for permanent pacing after TAVR, membranous septum length less than or equal to the non-coronary cusp implant depth was the strongest independent predictor.

Among 69 patients with short membranous septum length (<2 mm), there were no new pacemakers required among the eight with non-coronary cusp implant depth less than that length, compared with a 19.7% rate among the rest.

Among the 109 patients with a 2-5 mm membranous septum length, the rates were 8.2% versus 33.3%, respectively. In the 48 with longer membranous septa, the rates were 11.9% versus 33.3%.

After excluding patients with pre-existing right bundle branch block or first-degree atrioventricular block, the rates with medium or long membranous septa fell to 2.5% and 3.4% if the non-coronary cusp implant depth was less than the membranous septum length.

Implanting at the target depth of 3-4 mm kept the new permanent pacemaker implantation rate to 14.1% overall and to around 7-8% among those without the pre-existing conduction abnormalities.

Thus, Sultan's group concluded that best practices for Navitor valve placement are:

• Predilate to reduce need for resheathing and post-dilation
• Get an initial position with the inflow edge of the stent frame aligned with the base of the non-coronary cusp
• Confirm the implant depth in both cusp overlap and an alternate view to attain a target implant depth of 3 mm
• Withdraw the guide wire after deployment and confirm release of the three retainer tabs

"You obviously pay a price for the compromise of all these factors," noted session co-moderator Isaac George, MD, of NewYork-Presbyterian Columbia University Irving Medical Center in New York City. "Sometimes shooting for a very high depth is at that cost [of pop-outs]."

One pop-out required a second valve. "The recommendations based on the data is not really shooting for zero or one ... really shooting for a 2-4 mm depth," Sultan said.

"Little maneuvers here and there, we've learned over time I guess, will change that [permanent pacemaker implantation rate] a little bit," he told attendees. "But I think what we've seen over at least the last 100 or so, it has been consistent in the commercial experience."

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