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PARIS -- Left atrial appendage (LAA) occlusion with the Watchman device may be safe regardless of center experience, the EWOLUTION registry suggested.

Even though centers in the least experienced quartile were less likely to correctly size an implant on the first try (88.6% versus 98.8% for highest quartile, P<0.0001) and had lower odds of successfully releasing a device in one go (65.2% versus 84.4%, P<0.0001), centers of varying LAA occlusion experience showed no difference in overall procedural success.

Nor were there differences by center experience in 3-month outcomes, including pericardial effusion, tamponade, stroke, and device embolization, , of Germany's Cardiologicum Hamburg, reported at the annual .

"The registry shows high success rates in both highly-experienced centers and those with less experience," Bergmann concluded at a late-breaking trial session.

Bergmann's prospective investigation included information from 1,025 Watchman recipients throughout Europe, Russia, and the Middle East. Devices were implanted from 2013 through 2015 to prevent stroke in patients with atrial fibrillation.

Panelist , of Sunninghill and Sunward Park Hospitals in Johannesburg, suggested to the audience that the learning curve for LAA occlusion is flattening out. He cited improvements in procedural success and complication rates in recent years, commenting that "this reflects successful device rollout and training."

, of Scripps Clinic in La Jolla, Calif., agreed. "This is more proof that the training regime implemented by the device manufacturer has allowed the technology to be introduced safely at sites without prior experience," he told 番茄社区app.

There was a 98.9% rate of fully sealed LAAs by procedure's end. Bergmann attributed this "phenomenal" result to the "rule of thumb" of sizing devices two sizes up to achieve a 20% compression of each device by diameter.

While 85.7% of patients had no reported events by 3 months, the bulk of those that did occur were not attributed to Watchman implantation, Bergmann's group found. Device-related events were reported for 3.2%. Bleeding was the most common adverse event, occurring in 4.1% of cases, followed by device thrombosis at 2.8% and death at 2.4%.

At 4.1%, however, bleeding was "not insignificant," Hellig emphasized. Most patients implanted in the registry were at high bleeding risk and deemed ill-suited for warfarin (Coumadin).

Severe adverse events were equally likely among recipients of different anticoagulation regimens, even those who received nothing. "You can say that there's a point to giving a patient nothing if there's a very high bleeding risk," Bergmann suggested.

Still, "dual antiplatelet therapy [DAPT] and novel oral anticoagulant [NOAC] therapy are feasible and safe during the first 3 months," he added.

Hellig commented: "Patient characteristics are likely to dictate drug choices, though rates were numerically low for both thrombus and bleeding with NOACs. I think this is important."

"Could post-procedure NOACs be the best option? We now know that dabigatran [Pradaxa] has an antidote," he continued.

Xavier Freixa, MD, of Hospital Clinical of Barcelona, Spain, told 番茄社区app in an interview that "NOACs can be a safer alternative to DAPT, though not necessarily at full dose, since it requires more testing. NOACs are very well-tolerated in many patients with bleeding risk, but there are populations -- those with frailty, renal insufficiency, for instance -- where NOACs can be a problem."

Indeed, anticoagulation will remain a burning question pending future randomized studies, Freixa suggested. In the present study, "they treated completely different patients with different risks."

"It is perhaps too early to recommend NOAC only for the post-procedural period, but this would be important next step to look at. For LAA closure to reach its full potential in reducing bleeding, the ideal would be to omit aspirin in the long term," according to Hellig. In any case, "it appears to be safe to omit warfarin," he added.

"In conclusion, LAA occlusion seems to work. It's something that's here to stay and grow and expand," Freixa said.

A U.S. registry for LAA closure was mandated as part of Medicare coverage of the Watchman device.

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