Antithrombotic Therapies Shifting for Watchman LAA Occlusion

A new study finds clinicians are shifting away from the FDA-approved combination of warfarin and aspirin after left atrial appendage occlusion (LAAO) with the Watchman device and that adverse events, particularly bleeding, are lower when aspirin is dropped.

Of 31,994 patients successfully implanted with the Watchman 2.5 device in the 3 years after its March 2015 approval, only 1 in 10 received the full postprocedure protocol studied in pivotal trials and codified into the US Food and Drug Administration (FDA) device approval.

The protocol consisted of aspirin (81 to 325 mg) indefinitely and warfarin for 45 days. Following transesophageal echocardiography, patients were then maintained on warfarin and aspirin if there was a peridevice leak greater than 5 mm or switched to clopidogrel 75 mg for 6 months if a peridevice leak was ruled out or was 5 mm or less.

Based on the results, drawn from the National Cardiovascular Data Registry (NCDR) LAAO Registry, the most common discharge medications were warfarin and aspirin in 36.9% of patients, followed by a direct oral anticoagulant (DOAC) and aspirin (20.8%), warfarin alone (13.5%), DOAC only (12.3%), and dual antiplatelet therapy (DAPT) with aspirin and a P2Y₁₂ inhibitor (5%).

"There's a little bit of practice leading the science in this space," lead author James V. Freeman, MD, MPH, Yale School of Medicine, New Haven, Connecticut, told theheart.org | Medscape Cardiology.

Patients who couldn't tolerate long-term anticoagulation were excluded from the pivotal trials but are now the patients in whom the device is most often used, because of the Centers for Medicare & Medicaid reimbursement mandate for a relative or absolute contraindication to long-term anticoagulation, he noted.

Not surprising, 70% of patients in the registry had history of clinically relevant bleeding, the mean CHA₂DS₂-VASc score was 4.6, and mean HAS-BLED score was 3. At an average age of 76, they were also older, by years, than those in the clinical trials.

Secular trends at the time also saw the ascendancy of the DOACs relative to warfarin, observed Freeman. "So I think it's pretty reasonable for physicians to be considering DOACs rather than warfarin in this context."

Aspirin Takes Another Hit

Results, published May 2 in the Journal of the American College of Cardiology, showed that any adverse event occurred at 45 days in 5.7% of patients discharged on warfarin and aspirin, 4% on warfarin alone, 5.2% on DOAC and aspirin, 3.8% on DOAC only, and 5.5% on DAPT.

Rates of any major adverse event were 4.4%, 3.3%, 4.3%, 3.1%, and 4.2%, respectively, and for major bleeding were 3%, 1.8%, 2.8%, 1.7%, and 2.2%, respectively. Although patients were similar across treatment groups, those treated with DAPT were slightly older and had more comorbidities, Freeman said.

In Cox frailty regression, the adjusted risk of any adverse event at 45 days was significantly lower when patients were discharged on warfarin alone (hazard ratio [HR], 0.692; 95% CI, 0.56 - 0.84) and a DOAC alone (HR, 0.731; 95% CI, 0.57 - 0.93), compared with warfarin and aspirin. There were no differences among the other groups.

The risk of any major adverse event was also significantly lower with warfarin alone (HR, 0.658; 95% CI, 0.53 - 0.80) and DOAC alone (HR, 0.767; 95% CI, 0.59 - 0.98).

At 6 months, rates of any adverse event (HR, 0.814; 95% CI, 0.72 - 0.93) and any major adverse event (HR, 0.840; 95% CI, 0.73 - 0.95) were significantly lower only in patients treated with warfarin alone.

"I think if there's a take-home [message] here, it's that for a lot of patients there's good data now to suggest getting rid of the aspirin is a very reasonable thing to do," Freeman said.

Further studies are needed in the space, but the results are consistent with those from transcatheter aortic valve replacement studies showing discharge on warfarin or DOAC anticoagulation alone reduces major adverse events without increasing thrombotic events, he said.

"I do think if there's a strong indication for aspirin — someone has terrible coronary disease — there may be a role for using it," Freeman said. But for a lot of these patients, anticoagulation alone without aspirin "may present a big opportunity to mitigate morbidity associated with this procedure."

Freeman said he doesn't expect the findings would be dramatically different with the second-generation Watchman FLX device but noted that randomized data will be forthcoming, as Boston Scientific changed the CHAMPION-AF trial protocol to include DOAC alone without aspirin.

Commenting for theheart.org | Medscape Cardiology, Domenico Della Rocca, MD, Texas Cardiac Arrhythmia Institute at St. David's Medical Center, Austin, said the study is a useful overview of post-LAAO therapies in a large population — but not surprising.

"Practice has changed over the years. More and more we are adopting and trusting the DOACs," he said. "And, we are realizing that dual antiplatelet therapy is so aggressive and antiplatelet therapy alone maybe is not the best choice based on data on activation of coagulation."

Commenting further, he said "I think it's too early to suggest being too keen to completely drop aspirin," noting that 20%–25% of patients have clopidogrel resistance and that the combination of two antiplatelets may be too aggressive a strategy for others.

Della Rocca and colleagues recently reported favorable long-term results with half-dose DOAC therapy after Watchman implantation and said the team is launching a randomized trial in more than 500 LAAO patients in the US and Europe later this year. The trial will be comparing a DOAC-based strategy with low-dose apixaban long-term vs clopidogrel and aspirin initially, and then switching to 100 mg aspirin long-term.

"We hope that in the next 2-3 years we will have some better answers, but at this point I would say that clopidogrel is kind of an obsolete strategy for appendage closure," Della Rocca said.

In an accompanying editorial, David R. Holmes Jr, MD, Mayo Clinic, Rochester, Minnesota, says "the cornucopia of these specific strategies can be expected to change as practices evolve, as instructions for use broaden and, hopefully, with the results of well-done, scientifically performed trials. This current LAAO Registry report, however, serves as a useful benchmark."

He cautioned that this is an observational cohort study and that unmeasured imbalances still may affect the ability to identify an unbiased treatment signal. The use of DAPT was also infrequent during the study and "conclusions based on this information are soft."

The study was funded by the American College of Cardiology (ACC) National Cardiovascular Data Registry (NCDR) and the National Heart, Lung, and Blood Institute (NHLBI) grants. Freeman has received salary support from the ACC NCDR and the NHLBI; and has received consulting/advisory board fees from Boston Scientific, Medtronic, Janssen Pharmaceuticals, and Biosense Webster.

J Am Coll Cardiol. Published online May 2, 2022. Full Text, Editorial

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