New Real-World Data Bolster Safety of Watchman FLX in LAAO

Patrice Wendling

May 02, 2022

In-hospital safety and procedural outcomes for percutaneous left atrial appendage (LAA) closure are substantially better with the Watchman FLX device than with its predecessor, new research shows.

Data from more than 50,000 patients in the National Cardiovascular Data Registry (NCDR) LAA Occlusion Registry showed the rate of any in-hospital major adverse events was cut in half, from 2.4% with the first-generation Watchman 2.5 device to 1.35% with the next-generation device (P < .001).

This was driven largely by a drop, from 1.2% to 0.4%, in rates of pericardial effusion requiring intervention, an Achilles heel of the procedure, James V. Freeman, MD, MPH, reported during a late-breaking clinical trials session at the Heart Rhythm 2022 meeting in San Francisco.

Downstream consequences of these leaks, such as in-hospital death, major bleeding, and cardiac arrest, were lower with the Watchman FLX.

The redesign also appears to ease implantation, with rates of implant, device, and procedural success 1% to 2% higher.

"The risk of the procedure is substantially reduced with this device, so I think it lowers the barrier to using it in patients who have an indication," Freeman, director of the atrial fibrillation program and the electrophysiology laboratories at Yale School of Medicine, New Haven, Connecticut, told | Medscape Cardiology.

Recently reported 45-day outcomes from the same registry were favorable and in line with clinical trials data. Some cardiologists, however, question the net clinical benefit of a preventive procedure to reduce stroke in patients with atrial fibrillation, citing the potential for harm, divergent results in pivotal trials, and leaving a foreign body behind in the heart.

"There's a role for being skeptical when you have a new procedure, but I think these new data are really reassuring that this device has now gotten markedly safer," Freeman added. "I think it changes our calculus around what's the risk profile of the procedure and in terms of its risk–benefit."

Freeman noted that as part of its August 2020 commercial rollout of the Watchman FLX, Boston Scientific asked centers to turn in their old Watchman devices within a month of performing their first FLX case. This allowed for a natural experiment-era analysis, in which the same number of Watchman 2.5 cases, done immediately preceding the first FLX procedure, were included per site as Watchman FLX cases.

As the sites, operators, and procedure indications remained the same, the two groups of 27,013 patients were "remarkably well balanced," he said. Their mean age was 76 years, mean CHA2DS2-VASC score was 4.8, and 22% to 23% had a previous stroke.

The primary outcome of in-hospital major adverse events was a composite of death, cardiac arrest, stroke, transient ischemic attack (TIA), ischemic stroke, systemic embolism, major bleeding, major vascular complication, myocardial infarction, pericardial effusion requiring intervention, and device embolization.

Patients treated with the Watchman FLX, compared with the 2.5 device, had significantly lower rates of in-hospital death (32 vs 57 cases), device embolization (6 vs 17 cases), cardiac arrest (36 vs 64 cases), and major bleeding (293 vs 553 cases).

Rates of ischemic stroke (24 vs 18 cases) and TIA (7 vs 3 cases) were numerically higher with the Watchman FLX, whereas the hemorrhagic stroke rate was lower (1 vs 4 cases).

Myocardial infarction trended lower with the Watchman FLX (5 vs 8 cases), as did major vascular complications (35 vs 50 cases).

"We would not expect any of these to be impacted by the redesign of this device, and this is really reassuring when you're looking at an observational study," Freeman said during his presentation.

Rates of peri-device leak greater than 5 mm were numerically lower with the Watchman FLX than with the Watchman 2.5 (0.03% vs 0.06%; P = .234).

Just last month, the researchers reported that leaks smaller than 5 mm after LAA closure with the Watchman 2.5 were associated with a higher incidence of thromboembolic and bleeding events, whereas larger leaks were not.

During a press briefing before the formal presentation, Freeman said it was a "real signal" toward an increased risk for thromboembolic events. "So, one of the potential benefits here is with this newer device, we may be able to optimize positioning, have a lower rate of small leaks, and potentially have an impact on thromboembolic events. We will be looking at that, but we don't have that yet."

In multivariate regression analysis, adjusted odds ratios remained significantly lower with the Watchman FLX for any in-hospital major adverse event (0.57; P < .001), death (0.59; P = .016), pericardial effusion requiring intervention (0.34; P < .001), cardiac arrest (0.59; P = .012), and major bleeding (0.53; P < .001).

The findings were almost identical in a propensity-score-matched analysis that matched each Watchman FLX patient with up to two Watchman 2.5 patients on age, sex, and propensity score, Freeman said.

In terms of procedural outcomes, the Watchman FLX device had higher rates of implant success (97.7% vs 96.8%; P < .001), device success (97.4% vs 96.6%; P < .001), and procedural success (96.1% vs 94.6%; P < .001).

"Yes, the success rate increased by 1%, the procedure was 3.8 minutes faster, but I think what's really striking is the safety," said discussant Vivek Reddy, MD, director of cardiac arrhythmia services for Mount Sinai Hospital and the Mount Sinai Health System in New York City.

He said the 50% reduction in major adverse events is “pretty extraordinary when you think about the number of operators performing this procedure around the country." The cardiac tamponade rate was also "quite remarkable," coming from 1.2% to 0.2%, and mortality was halved, from two in 1000 to one in 1000.

Reddy noted that recent NCDR data suggest the leak rate after appendage closure with the Watchman FLX is about 10%, which is much lower than that initially seen with the older 2.5 device.

"The question is will that actually translate into better clinical outcomes," he said. "There are emerging data that when we don't have leaks, we may have extremely low ischemic stroke rates. So, we have to see what happens in this registry."

The study was supported by NHLBI grants and Boston Scientific, which had no role in the design, conduct, submission, or presentation. Freeman reports research funding/salary support from the National Heart Lung and Blood Institute (NHLBI) and American College of Cardiology; serving on the advisory board/consulting (modest) for Medtronic, Boston Scientific, Biosense Webster, and PaceMate; and equity in PaceMate.

Heart Rhythm Society (HRS) 2022: Abstract LB-736-02. Presented May 1, 2022.

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