Patrice Wendling

May 19, 2016

PARIS, FRANCE — The first-generation Watchman (Boston Scientific) left atrial appendage (LAA) closure device provided high success and safety rates at the 3-month mark in real-world experience with patients at high risk of bleeding, including those treated at inexperienced centers or with no postprocedure anticoagulation[1].

The device was successfully implanted in 98.5% of 979 patients enrolled in the EWOLUTION study from 47 centers across Europe, Russia, and the Middle East.

At 3 months, 16% of patients had a significant adverse event (SAE), but only 0.5% experienced a device-/procedure-related event or one of unknown cause that resulted in death or other residual effects. "So, in fact, LAA closure is now as safe as if you give your patient an electrophysiologic pulmonary vein isolation," study author Dr Martin Bergmann (Cardiologicum Hamburg, Germany) said at EuroPCR 2016.

The Watchman device was approved in the US in March 2015 for the prevention of stroke in patients with atrial fibrillation (AF) after a bumpy road, and last month European sales of the FLX, a later generation of the device Watchman FLX, a later generation of the device, were suspended over embolism concerns.

High-Risk Population

Dr Martin Bergmann

Bergmann said the study enrolled a high-risk population, with 72% of patients having a contraindication for oral anticoagulation, 49% a CHA2DS 2-VASc score >5, and 26% aged >80 years. Contrary to other Watchman trials that mandated warfarin for 45 days postprocedure, 6.6% of patients were on no postimplant anticoagulation.

There was no significant effect of center experience on procedural success or complications at 3 months.

Device- or procedure-related adverse events were "very rare," occurring in 42 patients, with thrombus on the device reported in 20 patients, pulmonary embolism/cardiac tamponade in seven, and stroke in four. Bleeding, however, occurred in 38 patients (4.1%), "and this points to the fact that in this group we need to pay attention to the postimplant drug therapy," he said.

When the SAEs were stratified for postimplant drug therapy, there was no significant impact on all SAEs or the individual events, regardless of whether patients were on warfarin (n=159), single antiplatelet therapy (APT) (n=72), dual APT (n=607), novel oral anticoagulants (NOACs) (n=113), or nothing at all (n=67).

Bleeding was lowest, however, with the NOACs, at 1.9%, followed by dual APT (3.6%), warfarin (4.8%), nothing (6.7%), and single APT (7.2%), Bergmann said.

"Dual-antiplatelet therapy and NOACs are feasible and safe during the first 3 months," he concluded.

Next Piece of the Puzzle

Invited discussant Dr Farrel Hellig (Sunninghill and Sunward Park Hospitals, Johannesburg, South Africa) said the EWOLUTION study enrolled the right population, with a high risk of bleeding and stroke. The high implant-success rate reflects successful device rollout and training, surpassing implant rates of 88% and 91% reported in the earlier PROTECT-AF and PREVAIL trials with the Watchman device.

On the flip side, "The most important topic was the 4.1% bleeding rate at 3 months," which "was not insignificant" and will require more time "to evaluate this outcome," said Hellig.

With regard to postimplant drug therapy, it appears "acceptable to omit warfarin," he said. It is difficult to determine the effect of postimplant drug therapy on thrombus on the device and bleeding SAEs because patient characteristics likely dictate drug choices, although rates were low for both thrombus and bleeding with NOACs.

"The most important thing to know next is whether postprocedure NOACs could be the best option. We know that dabigatran [Pradaxa, Boehringer Ingelheim] now has an antidote. Can aspirin be omitted in the long term?" he asked, noting recent AVERROES trial data showing no difference in long-term bleeding rates between apixaban (Eliquis, Bristol-Myers Squibb/Pfizer) and aspirin.

"For LAA closure to reach its full potential to reduce bleeding, the ideal would be to omit aspirin long term, and I think a trial of NOAC only for a postprocedure period with no aspirin to follow would be the next piece of information we need to complete the puzzle."

Bergmann told reporters in a press briefing that the EWOLUTION data should overcome some of the hesitancy concerning the Watchman device and support LAA closure "as a routine procedure for stroke prevention in atrial fibrillation," even in patients not on anticoagulation. He balked, however, at saying patients can go without some form of postprocedure coverage, noting that DAPT has become routine practice for these patients in Europe.

The study was funded by Boston Scientific. Bergmann reports serving as a consultant for Boston Scientific and Biosense Webster and receiving honoraria from Bayer Pharma, Biotronik, Boehringer Ingelheim, Daiichi Sankyo, Eli Lilly, Novartis, and St Jude Medical. Hellig reported serving as a proctor for and receiving honoraria from Boston Scientific.

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