SWISS-APERO: better rates of device-related leak with AMULET, but higher procedural complications when compared to WATCHMAN FLX.

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By Wally A. Omar, MD on

Key Points

    • To determine success of percutaneous left atrial appendage occlusion (LAAO), residual patency of the appendage is assessed at 45 days, either via transesophageal echocardiogram or cardiac CT-A.
    • AMULET IDE showed that the Amulet device was noninferior to the Watchman device in preventing residual leak. This trial, however, did not assess the newer generation Watchman FLX device, one of the main counterarguments to the results.
    • Participants in this study were randomized to receive either the Amulet device or Watchman FLX for left atrial appendage occlusion. Device leak and appendage patency was assessed at 45 days by Cardiac CT-A.
    • At 45 days, the Amulet device was no different to Watchman when comparing patent appendages, but did have fewer rates of intra-device leak and mixed leak when assessed by TEE. Procedure-related complications, including death, CVA, major bleeding, and pericardial effusion were all higher in the Amulet arm when compared to the Watchman arm.

The AMULET device has gained traction over the past several months, after results of AMULET IDE were published, making it the main competitor to the Watchman left atrial appendage occlude (LAAO) across the globe. In clinical practice, success in LAAO is assessed by performing a transesophageal echocardiogram or cardiac CT-A, looking for device leak and/or left atrial appendage patency. The authors of SWISS-APERO sought to answer what they felt to be two clinical limitations of the AMULET IDE trial: the use of TEE instead of CT-A to determine appendage patency, and the use of Watchman as opposed to Watchman FLX as the comparator group.

The results of the trial were presented as a late-breaker during the 33rd annual TCT conference in Orlando, Florida by Dr. Roberto Galea (Bern University Hospital, Switzerland). This unblinded randomized control trial was performed at 8 centers across 4 countries in Europe. Participants were first screened for LAAO (high bleeding risk, appropriate appendage anatomy, no LAA thrombus). They were then randomized to receive either the Amulet device or Watchman FLX, followed by antithrombotic therapy of choice (Aspirin, clopidogrel, or a NOAC).

The primary endpoint was a composite of justified crossover to the non-randomly allocated device (in the case of difficult anatomy or device embolization) and LAA patency at 45-day CCTA. LAA patency was determined by centrally adjudicated methods, using a CT cutoff of LAA density ≥100 HU or ≥ 25% of the left atrium. Secondary outcomes included peridevice leak at 45 days, device-related thrombus at 45 days, procedural complications, and clinical outcomes (CV death, stroke, systemic embolization, and all bleeding).

221 patients were enrolled into the trial and randomized into either arm. Participants were mostly male, with a mean age of 76-77 years. All participants had a CHADS-VASC of at least 4, and HAS-BLED score of at least 3. For the primary endpoint of appendage patency at 45 days, there was no significant difference between AMULET and WATCHMAN FLX (67.6% vs 70%, HR 0.97 [0.8 – 1.16, p = 0.71]).  When assessed by TEE, however, AMULET was associated with lower rates of PDL (13.7% vs. 27.5%, HR 0.5 [0.27-0.9, p = 0.02]). When a leak was identified, AMULET was associated with higher rates of intradevice leak and WATCHMAN was associated with mixed intradevice and peridevice leak. Important secondary outcomes of note were device related thrombus, which were trended higher in the Watchman arm (3.0% vs 0.9% for definite DRT, 9.9% vs 3.7% for possible DRT).

Amulet was associated with higher procedural complications: there were 2 deaths, 2 strokes, and 4 clinically relevant pericardial effusions compared to none of these complications in the Watchman arm. When discussing these complications, Dr. Galea stated “We did indeed have higher rates of complications when compared to the AMULET IDE trial. We included events over 7 days as procedural-related, and had a higher-risk population, as almost 90% had prior bleeding”.  The panel agreed that while the procedural complications were higher, the study itself was timely, as Watchman FLX is the current market comparator to AMULET.

The results were published in CIRCULATION.

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