Amulet vs Watchman Comparison Still Muddy Any Which Way LAA Leaks Are Defined

SAN FRANCISCO — Two mainstream devices for percutaneous left atrial appendage (LAA) closure continued to lead to similar clinical outcomes in the SWISS-APERO trial.

Among patients randomized to the Amplatzer Amulet and the Watchman 2.5/FLX, the incidence of patent LAAs at 13 months reached 53.6% and 48.8%, respectively, on coronary CT angiography (risk ratio [RR] 1.10, 95% CI 0.81-1.48), reported Roberto Galea, MD, of Bern Inselspital in Switzerland.

Using various definitions of residual device leaks, Galea’s team still found no difference between the Amulet and Watchman 2.5/FLX groups:

• Intra-device leaks (IDL): 23.8% vs 17.5% (RR 1.36, 95% CI 0.74-2.51)
• Side gap-leaks (the composite of peridevice leaks and mixed leaks): 28.6% vs 27.5% (RR 1.04, 95% CI 0.64-1.70)
• Patent LAA with no visible leak: 7.1% vs 12.5% (RR 0.57, 95% CI 0.22-1.50)

Galea presented the data during a press conference at the Transcatheter Cardiovascular Therapeutics meeting hosted by the Cardiovascular Research Foundation. The findings from SWISS-APERO were simultaneously published in Circulation.

Dhanunjaya Lakkireddy, MD, of the Kansas City Heart Rhythm Institute at HCA Midwest Health in Missouri, took issue with the study’s “hairsplitting” of different LAA leak types that have little or no clinical implications and lead to confusion. “The definitions used unnecessarily complicate the way we call something a leak or not. Looking at these numbers, I think what matters is peridevice leaks … that is, leak around the device,” he told MedPage Today.

Unlike the Watchman, the Amplatzer Amulet consists of a lobe attached to a disc for better suitability for different LAA anatomies.

Device leaks in SWISS-APERO were defined as the presence of visible contrast medium along the entire or part of the length of either occluder.

Lakkireddy explained that peridevice leaks should be defined differently for the Amulet due to the possibility for flow around the disc without any flow through the lobe. “It is not surprising to see that the IDL is high with Amulet because it has a larger surface area and thus takes longer for endothelialization. There is more contrast flowing through but it is really not a leak,” he noted.

The main SWISS-APERO results presented 2 years ago had shown that Watchman 2.5/FLX and Amplatzer Amulet performed similarly for peridevice leaks. Separately, at that time, it was announced that the Amplatzer Amulet outperformed Watchman on peridevice leaks 12 months into the Amulet IDE trial — albeit using a more standard imaging modality — transesophageal echocardiography — and testing against mostly older Watchman 2.5 devices.

LAA occlusion is performed to prevent thromboembolic events in patients with atrial fibrillation (Afib) who are at high risk of bleeding. In his report, Galea showed comparable clinical event rates between the Amulet and Watchman arms of the trial:

• Cardiovascular death, ischemic stroke, and systemic embolism: 9.5% vs 10.2% (HR 0.91, 95% CI 0.39-2.14)
• Cerebrovascular events: 2.7% vs 3.7% (HR 0.75, 95% CI 0.17-3.35)
• Bleeding: 40.8% vs 31.4% (HR 1.46, 95% CI 0.93-2.28)

Also similar were findings of device-related thrombosis on coronary CT angiography (2.4% vs 3.8%; RR 0.63, 95% CI 0.11-3.70).

It’s “good news” that there is not much difference in ischemic strokes, Lakkireddy said, and the study reconfirms findings of the Amulet IDE trial for which he was principal investigator.

He noted that the vast majority of patients in clinical practice can be occluded with either a Watchman or an Amulet device, and there is “no fundamental difference between the two.” In the remaining 15%, the Amulet may be preferred for abnormal anatomy — such as a very proximal lobe next to the orifice or a very shallow appendage that does not have enough depth — or the desire to stop anticoagulation right away after device implant.

SWISS-APERO targeted patients whose LAA anatomies would have been suitable for either study device.

The trial included Afib patients with CHA₂DS₂-VASc scores ≥2 and either HAS-BLED scores ≥3 or existing high bleeding risk features. The 221 participants were randomized to either Amulet or Watchman devices; those in the latter group received Watchman 2.5 devices until October 2019 (n=25), after which the study proceeded with Watchman FLX for this study arm (n=85).

For their prespecified analysis of the SWISS-APERO trial, Galea and colleagues relied on the roughly three-quarters of the cohort who underwent 13-month coronary CT angiography.

Results remained consistent when only patients with Watchman FLX were compared with Amulet, the investigators said.

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