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With accumulating experience in transcatheter aortic valve replacement (TAVR) has come largely better outcomes in the U.S. and France, although tamponade and pacemaker requirements have risen, two studies confirmed.

In the U.S. Transcatheter Valve Therapy (TVT) Registry, higher TAVR site case volumes were tied linearly to on adjustment (P=0.023), John D. Carroll, MD, of the University of Colorado Denver and colleagues reported in the July 4 issue of the Journal of the American College of Cardiology.

Increasing site experience was also tied to fewer vascular complications (P=0.003) and less bleeding (P<0.001), albeit non-linearly: The sharpest drop in event rates occurred within the first 100 cases, after which reductions continued but more gradually.

Over a team's first 400 cases, there tended to be declining rates of death (3.57% for first case to 2.15% for 400th), bleeding (9.59% to 5.08%), vascular complications (6.11% to 4.20%), and stroke (2.03% to 1.66%).

"The initial adoption of TAVR into practice in the United States showed that increasing experience was associated with better outcomes. This association, whether deemed a prolonged learning curve or a manifestation of a volume–outcome relationship, suggested that concentrating experience in higher volume heart valve centers might be a means of improving outcomes," concluded the researchers.

Their study of the TVT Registry included 42,988 TAVR procedures performed from 2011 through 2015 at 395 sites. The median age of the high-risk participants was 83 years; 51.0% were men.

A major limitation of the study is that it didn't count case volume from investigative studies, such that centers participating in early clinical trials were well past their learning curves by the time the TVT Registry was created.

Tamponade and Pacing Concerns in France

French operators are also getting better at avoiding TAVR complications over time, although tamponade and pacing requirement risks have risen, according to a separate study in the same journal.

Over a 6-year period covered by two national registries there -- first the FRANCE 2 TAVR registry and then the FRANCE TAVI registry -- there was a halving of in-hospital mortality (8.1% for FRANCE 2 to 4.4% for FRANCE TAVI, P<0001) and 30-day mortality (10.1% to 5.4%, P<0.001).

Strokes and serious complication risks remained flat over time, while increases were seen in cardiac tamponade (1.3% to 2.0%, P=0.004) and pacemaker implantation rates (12.6% to 17.5%, P<0.001), according to Hervé Le Breton, MD, of Centre Hospitalier Universitaire Pontchaillou in Rennes, France, and colleagues.

"These rates compared favorably with those of FRANCE 2 and probably reflected a more refined selection of lower–surgical risk patients, improved procedural planning and execution, newer iterations of transcatheter devices, and enhanced post-procedural care," Le Breton's group said.

"Nonetheless, given that TAVR indications are likely to expand to patients at lower surgical risk, concerns remain regarding potentially life-threatening complications and pacemaker implantation."

FRANCE 2 covered TAVR performed in 2010 through 2012 at 34 centers (n=4,165), FRANCE TAVI included those done in 2013 through 2015 at 48 centers (n=12,804). The median age was 84.6 years on enrollment, with 49.7% of patients being men.

Participants in the later registry were older but at lower surgical risk, according to Le Breton and colleagues.

Device success saw a small boost from 95.3% in FRANCE 2 to 96.8% in FRANCE TAVI (P<0.001). There was more transfemoral TAVR (73.4% to 82.8%). Procedures were increasingly being performed in hybrid operating rooms (15.8% to 35.7%, P<0.001).

Meanwhile, general anesthesia was less common (68.7% to 51.7%, P<0001), as was transesophageal echocardiography guidance (60.7% to 32.3%, P<0.001).

The study had potential for selective reporting, given Le Breton's group was working with site-reported data without external adjudication.

Don't Forget Valve Durability, TAVR Pioneers Say

"For the pioneers who remember the beginning of the story, marked by the fierce opposition of all experts toward a so-called totally unrealistic and stupid idea, and who also had to face the incredibly challenging clinical pathway imposed by health authorities for clinical evaluation, such important real-world registries are particularly meaningful," said the group that performed the first TAVR in 2002.

The bump in pacemaker rate likely came about "from the early and increasing use of the Sapien 3 valve before its implantation height was modified," Alain Cribier, MD, of France's Rouen University Charles Nicolle, and colleagues suggested in a linked editorial.

TAVR's bigger hurdle, it seems, may come with TAVR expanding to lower-risk and younger patients: "long-term durability of the valves is the unanswered question that remains to be addressed before extension of indication to patients with long life expectancy."

"Concentrating experience in high-volume centers should be favored to improve outcomes, more particularly when TAVR is likely to expand to lower-risk or younger patients," Cribier's group said.