Discussion
AF is the most common cardiac arrhythmia in advanced age and is associated with the risk of intracardiac thrombus formation and the occurrence of stroke. OAC is still the standard therapy for patients with AF who have an increased risk of stroke.3 However, a number of patients with AF develop bleeding complications that require discontinuation of OAC. In this situation, interventional closure of the LAA represents an established treatment alternative.7
Since the early days of LAAC, a number of improvements have been implemented into new devices and interventional strategies so that the procedure of LAAC has become both more effective and safer.5 8 One of the most recent developments was the introduction of the WM FLX device, which has received Food and Drug Administration (FDA) approval in 2020. Data from the Protection Against Embolism for Nonvalvular AF Patients: Investigational Device Evaluation of the Watchman FLX LAA Closure Technology (PINNACLE) trial reported positive clinical data regarding the efficacy and safety of the new device.5
The aim of our study presented here was to describe which changes in procedural data as well as during echocardiographic follow-up can be observed when an implanting centre switches from using the WM V.2.5 to the WM FLX.
Although there are several differences in the implantation procedure between the two occluder types,5 this obviously does not translate into relevant changes in procedure time, use of contrast medium or radiation dose, respectively, which all were comparably between the two groups and within the range of previous reports.9 In parallel, positioning of the two devices directly after implantation was found to be very similar in TEE without any signs of systematic differences. This also applies for the depth of implantation, which is of prognostic importance with WATCHMAN devices in order to avoid an uncovered LAA neck, which otherwise might harbour a risk of embolic events. However, two details of the appearance of the WM FLX differ from its precursor, the covering membrane has a thicker echocardiographic appearance and the connector seems to be more protruding in respect to the front surface of the device. During 3-month follow-up, these two echocardiographic differences were found less pronounced.
Regarding clinical end points, the use of the WM FLX was associated with favourable outcomes in our study as the occurrence of the combined endpoint of death, stroke/TIA/systemic embolism, tamponade, device embolisation and peridevice leakage was reduced by 59% in comparison to WM V.2.5. In line with this, previous reports also described a numerically lower number of peridevice leakage in favour of WM FLX.10 11
Although especially for the WATCHMAN device, small leaks have been considered of no clinical relevance initially,12 there has been a large retrospective study recently which has found a modestly higher incidence of thromboembolic events in patients after LAAC with residual leaks <5 mm.13
So far, only limited data is available regarding risk factors that predict the occurrence of PDL after percutaneous LAAC.14–16 Previous studies were describing LAA size15 or eccentricity of the LAA14 as a major determinant in the development of PDL, which, however, are variables that cannot be influenced by the LAAC procedure itself. In contrast, our data indicates that minimal device compression at the time of implantation seems to be of special importance as this parameter was significantly linked to leaks at 3-month follow-up in a multivariate regression model whereas LAA size was not, a finding that had been described in a similar way before.16 Additionally, the data shows that after 3 months there were less PDL in the WM FLX group where we consistently found evidence of a more pronounced delayed device expansion as a potential explanation. Taken together, these findings argue for the importance of the radial force of the LAA occluder towards the surrounding tissue as an important factor to avoid the development of PDL.