Left atrial appendage occlusion with the Amulet device: to tug or not to tug?

PURPOSE: Left atrial appendage occlusion (LAAO) involves a "tug test," in which implanters pull on the device delivery cable to ensure stable occluder placement. The aim of this study was to evaluate the recommendation to perform the tug test, by comparing forces exerted on the device during deployment and subsequent tug test. A secondary objective was to simulate forces experienced on left atrial appendage tissue by placement of a 20-mm device. METHODS: The AMPLATZER™ Amulet™ device was used for occlusion. A force transducer recorded forces in the delivery cable during deployment and tug test in 23 patients. Four patients were excluded due to improper transducer placement or technical errors in data collection. For a 20-mm device, the force imparted on the circumferential contact with left atrial appendage wall tissue was simulated in a computational model, using the measured externally applied forces as inputs. RESULTS: For devices < 25-mm in diameter, disc deployment force (mean ± standard deviation) was 1.72 ± 0.43 N, and tug force was 1.01 ± 0.59 N. For devices ≥ 25 mm in diameter, disc deployment force was 2.96 ± 0.57 N, and tug force was 1.04 ± 0.24 N. The increase in disc deployment force compared with tug test force was statistically significant for small devices (< 25 mm; p = 0.049) and large devices (≥ 25 mm; p < 0.001). CONCLUSIONS: Increased force applied on the AMPLATZER™ Amulet™ device during disc deployment compared with during tug test was statistically significant, suggesting that the tug test is redundant in most cases for checking device stability.