Watchman LAA Closure Postmarket Results 'Remarkable,' Despite Cautions

Larry Hand

November 03, 2016

WASHINGTON, DC — Procedural success rates were high and major complication rates low in the postapproval study of the Watchman (Boston Scientific) left atrial appendage (LAA) closure device, despite the fact that a large proportion of implanting physicians were inexperienced with the device, according to study results presented at TCT 2016.

"The success rates across the board remain very high," Dr David Holmes Jr (Mayo Clinic, Rochester, MN) TCT 2016 presenter and senior author of the study published simultaneously in the Journal of the American College of Cardiology[1]. "We were able to train people very well."

"This data set represents the first patients implanted with this novel therapy," he added. "You'll never see a group like this again. Now we'll see a registry of patients going forward."

Even with a low complication rate, "we have a high degree of confidence that we captured the majority of complications," Dr Vivek Y Reddy (Mount Sinai Hospital and Carl Icahn School of Medicine, New York), first author of the study, said via a video link during the presentation.

Reddy, Holmes, and colleagues analyzed outcomes for 3822 patients who underwent implantation of the Watchman device between March 2015 and May 2016. The Food and Drug Administration approved Watchman device in March 2015 as a preventive measure against stroke in patients with atrial fibrillation.

Dr David Holmes

A total of 382 physicians implanted the devices at 169 US centers. Almost three-quarters (71%) were newly trained and accounted for 50% of the procedures.

Due to FDA concern regarding potential safety issues, Boston Scientific required that a clinical specialist monitor all implantation cases and collect results of procedures and major complications, then report using a standardized process and forms. That allowed the researchers to collect data on all procedures after FDA approval but before a formal registry was certified.

Physicians successfully implanted the devices in 3653 patients (95.5%), with a median procedure time of 50 minutes.

Procedural complication rates were low: 1.02% (n=39) for tamponades, 0.078% (n=3) for procedure-related strokes, 0.25% (n=9) for device embolizations, and 0.078% (n=3) for procedure-related deaths.

"With half the procedures being done by otherwise-inexperienced operators, having a tamponade rate of 1% is really important," Reddy said. "A third of the tamponades did require surgical revision. And the three deaths that occurred were related to tamponades. Clearly, we do have some areas for improvement."

Dr William Gray (New York-Presbyterian Hospital/Columbia University), who was not involved in the study, told heartwire from Medscape, "The Watchman study was meant to look at the ability of the manufacturer to translate the therapy into the broader cardiology community [beyond clinical trials] in a safe and effective way. The data are quite remarkable. The safety signal is dramatically better than it's been in the past.

"Really, I think it proves to the benefit of patients. The margin of benefit really becomes how costly from a risk standpoint it is to put it in. When the risks drop, the benefits to the patients go up. That's successful transfer of a new technology into the larger community," Gray said.

In a related editorial published along with the Watchman study[2], Dr Jacqueline Saw (Vancouver Coastal Health Institute, BC) and Dr Matthew J. Price (Scripps Health, La Jolla, CA) point out that oral anticoagulants (OACs) for stroke prevention are one of the main treatments for atrial fibrillation but may cause bleeding.

They write that the new Watchman results "are remarkably favorable for the earliest phase of widespread dissemination of this technology, particularly in the context of the much higher rates of medication-related adverse events that occur with long-term OAC."

However, they write that the way the data were collected—manufacturer clinical specialist reporting—"may have resulted in potential bias and underreporting."


Dr David Hildick-Smith

In another presentation during the same TCT 2016 session[3], Dr David Hildick-Smith (Sussex Cardiac Centre, Brighton and Sussex University Hospitals, Brighton, UK) presented trial results for another LAA closure device in development, the Amplatzer Amulet (St Jude Medical).

The trial, conducted between June 2015 and September 2016 at 64 clinical sites in Europe, the Middle East, Asia, Australia, and South America, enrolled 1073 patients. After 13 were excluded, 1060 patients (average age 75) had device implantation, for a technical success rate of 98.8%.

Major adverse events occurring within 7 days included death (three, 0.3%), stroke (three, 0.3%), pericardial infusion (five, 0.5%), and bleeding (10, 0.9%). Two deaths were procedure-related. Overall 29 (2.9%) adverse events occurred.

The closure rate, per transesophageal echocardiography, came to 99%.

"The Amulet device has very high technical implant-success rates, and implantation is associated with low rates of periprocedural and early adverse events," Hildick-Smith said during the presentation.

"In the Amulet trial we're seeing very low rates of complications and we're seeing very low rates of death," Gray told heartwire . "Closure, at 3 months, is 100%, and you can't ask for better than that. We assume that that will translate into a stroke benefit going forward. This trial sets up nicely the US Amulet trial, which is a randomized trial against Watchman."

Boston Scientific funded this study. Reddy reported receiving grant support from and being a consultant for Boston Scientific, Coheres, Sentreheart, and St Jude Medical; Holmes reported having a financial interest in a related technology license to Boston Scientific. Editorialist Price reported consulting or speaker honoraria from multiple companies including Boston Scientific and St Jude Medical. St Jude Medical funded the Amulet study; Hildick-Smith reported consulting for St Jude Medical, Boston Scientific, and others.

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