Enhanced Thromboresistance and Endothelialization of a Novel Fluoropolymer-Coated Left Atrial Appendage Closure Device

Clinical effectiveness and safety comparison between direct oral anticoagulants and warfarin for nonvalvular atrial fibrillation patients following percutaneous left atrial appendage closure operation intervention: a prospective observational study

The main objective of this study was to investigate the optimal post-left atrial appendage closure (LAAC) anticoagulation strategy, focusing on minimizing device-related thrombosis (DRT) and thromboembolism (TE) events without increasing bleeding risk. After successful LAAC, consecutive participants were treated with 45-day anticoagulants (rivaroxaban 15 mg daily, dabigatran 110 mg twice a day, and warfarin). The efficacy endpoints included DRT, TE, and hospital readmissions due to cardiac caused, while safety endpoints encompassed bleeding events, monitored over a 12-month follow-up period. The incidence of DRT was relatively lower in the rivaroxaban group compared to both the dabigatran and warfarin groups (rivaroxaban vs. dabigatran: HR = 0.504, 95% CI 0.208-1.223, log-rank P = 0.101; rivaroxaban vs. warfarin: HR = 0.468, 95% CI 0.167-1.316, log-rank P = 0.093). The median [interquartile range] length and width of DRT in the rivaroxaban group were 1.92 [1.68-2.15] mm and 1.49 [1.28-1.76] mm, both significantly lower than those in the dabigatran (length = 2.15 [1.99-2.25] mm, P = 0.036; width = 1.60 [1.54-1.85] mm, P = 0.035) and warfarin groups (length = 2.26 [2.11-2.44] mm, P = 0.006; width = 1.74 [1.54-1.85] mm, P = 0.006). Kaplan-Meier survival analysis indicated that procedural bleeding was more common in the warfarin group. The 12-month incidence of TE was significantly lower in the rivaroxaban group compared to the dabigatran (HR = 0.466, 95% CI 0.221-0.984, log-rank P = 0.029) and warfarin groups (HR = 0.456, 95% CI 0.188-0.966, log-rank P = 0.042). Long-term antithrombotic therapy with reduced dose of rivaroxaban significantly reduced the risk of DRT and composite endpoints without increasing bleeding events, compared to warfarin and dabigatran, for patients following LAAC.

An International Consensus Practical Guide on Left Atrial Appendage Closure for the Non-implanting Physician: Executive Summary

Many patients with atrial fibrillation (AF) who are in need of stroke prevention are not treated with oral anticoagulation or discontinue treatment shortly after its initiation. Despite the availability of direct oral anticoagulants (DOACs), such undertreatment has improved somewhat but is still evident. This is due to continued risks of bleeding events or ischemic strokes while on DOAC, poor treatment compliance, or aversion to anticoagulant therapy. Because of significant improvements in procedural safety over the years left atrial appendage closure (LAAC), using a catheter-based, device implantation approach, is increasingly favored for the prevention of thromboembolic events in AF patients who cannot have long-term oral anticoagulation. This article is an executive summary of a practical guide recently published by an international expert consensus group, which introduces the LAAC devices and briefly explains the implantation technique. The indications and device follow-up are more comprehensively described. This practical guide, aligned with published guideline/guidance, is aimed at those non-implanting physicians who may need to refer patients for consideration of LAAC.

Transfabric Leaks After Percutaneous Left Atrial Appendage Occlusion Procedures with the WATCHMAN FLX Device

Background

Cardiac computed tomography imaging with contrast is being used increasingly to image left atrial appendage occlusion (LAAO) devices. Contrast flow across a device, also known as a transfabric leak (TFL), may indicate a lack of complete LAAO-device endothelialization. The data on the rate, predictors, and clinical events associated with TFL are limited.

Methods

All patients who underwent an LAAO-device implantation with a WATCHMAN FLX device and received a postimplantation computed tomography scan were included in this single-centre retrospective cohort study. Patients were classified as either having or not having a TFL, according to 3 currently proposed definitions of TFL. Clinical and procedural differences between the 2 groups were determined. An exploratory univariate logistic regression model to evaluate predictors of TFL was constructed.

Results

A total of 56 individuals were included in the cohort. The rate of TFL varied from 27% to 52%, depending on the radiographic definition employed. No clinically important patient or procedural characteristics were noted between the groups with vs without TFL. No predictors of TFL were identified. Six deaths and one stroke occurred during a median follow-up period of 673 days.

Conclusions

TFLs occur commonly post-LAAO procedures, suggesting that complete endothelialization of LAAO devices in humans may not be similar to that reported in animal models. Additional study into the best imaging approach to identify TFLs, and clinical events associated with TFLs, is necessary to clarify the significance of TFLs.

Comparative Endothelialization of the Watchman Plug Device and LACBES Pacifier Occluder after Left Atrial Appendage Closure

Background

For patients with nonvalvular atrial fibrillation (NVAF), left atrial appendage closure (LAAC) is an alternative to oral anticoagulants (OACs). However, incomplete device endothelialization (IDE) after LAAC has been linked to device-related thrombus (DRT) and subsequent thromboembolic events. Here, the differences in device endothelialization between the Watchman plug device and the LACBES pacifier occluder after implantation were investigated.

Methods

Of 201 consecutive patients with indications for LAAC, 101 received a Watchman 2.5 device, and 100 received a LACBES occluder. IDE was defined as a residual flow of contrast agent inside the left atrial appendage (LAA) on cardiac computed tomography angiography (CCTA) without peri-device leak (PDL) at the 3-month and 6-month follow-ups.

Results

There were no significant differences in DRT or PDL incidence between the two groups. However, the IDE rate in the absence of PDL was higher in the LACBES group than in the Watchman group at 3 months (42.4% versus 25.8%; p = 0.025) and at the 6-month follow-up (24.7% versus 11.2%; p = 0.028) as determined by CCTA.

Conclusions

Our findings indicated that the LACBES occluder took longer to complete endothelialization than the Watchman device after successful LAAC therapy. CCTA is a reliable imaging method for assessing the sealing of LAAC devices and confirming complete device endothelialization.

Association between preprocedural thromboembolic and bleeding events under oral anticoagulation therapy and mid-term outcomes after percutaneous left atrial appendage closure

Currently, no consensus has been established on the most effective antithrombotic therapy to prevent thromboembolic and bleeding events in patients undergoing percutaneous left atrial appendage closure (LAAC) with preprocedural thromboembolic or bleeding events under oral anticoagulation (OAC) therapy. We retrospectively investigated the incidence of device-related thrombosis (DRT), thromboembolic events, and bleeding events in patients who underwent LAAC from September 2019 to October 2022. After categorizing patients into three groups based on preprocedural thromboembolic or bleeding events under OAC therapy, we compared the incidence of DRT and prognosis according to the postprocedural antithrombotic therapy. In patients who received the conventional antithrombotic therapy (OAC with and without single antiplatelet therapy for 45 days after LAAC and dual-antiplatelet therapy from 45 days to 6 months followed by single antiplatelet therapy), preprocedural thromboembolic events despite OAC were independently associated with DRT or postprocedural thromboembolic events at the 3 year follow-up (hazard ratio [HR] 4.55; 95% confidence interval [CI] 1.32-15.6; P = 0.016), whereas preprocedural bleeding events were independently associated with postprocedural bleeding events (HR 8.01, 95% CI 1.45-58.3; P = 0.036). Continuation of OAC for 12 months among patients who developed preprocedural thromboembolic events during OAC significantly decreased the incidence of DRT or postoperative thromboembolic events (P = 0.002) with no increase in the bleeding events (P = 0.522). Preprocedural thromboembolic and bleeding events can predict adverse events after LAAC with the conventional antiplatelet-based antithrombotic therapy. Patients who develop thromboembolic events under continuous OAC may benefit from continuous OAC for 1 year after LAAC.

Left atrial appendage closure for stroke prevention in atrial fibrillation: current status and perspectives

Atrial fibrillation (AF) is associated with an increased risk of stroke and systemic embolism, and the left atrial appendage (LAA) has been identified as a principal source of thromboembolism in these patients. While oral anticoagulation is the current standard of care, LAA closure (LAAC) emerges as an alternative or complementary treatment approach to reduce the risk of stroke or systemic embolism in patients with AF. Moderate-sized randomized clinical studies have provided data for the efficacy and safety of catheter-based LAAC, largely compared with vitamin K antagonists. LAA device iterations, advances in pre- and peri-procedural imaging, and implantation techniques continue to increase the efficacy and safety of LAAC. More data about efficacy and safety of LAAC have been collected, and several randomized clinical trials are currently underway to compare LAAC with best medical care (including non-vitamin K antagonist oral anticoagulants) in different clinical settings. Surgical LAAC in patients with AF undergoing cardiac surgery reduced the risk of stroke on background of anticoagulation therapy in the LAAOS III study. In this review, we describe the rapidly evolving field of LAAC and discuss recent clinical data, ongoing studies, open questions, and current limitations of LAAC.

Position Statement on Cardiac Computed Tomography Following Left Atrial Appendage Occlusion

Left atrial appendage occlusion (LAAO) is rapidly growing as valid stroke prevention therapy in atrial fibrillation. Cardiac imaging plays an instrumental role in preprocedural planning, procedural execution, and postprocedural follow-up. Recently, cardiac computed tomography (CCT) has made significant advancements, resulting in increasing use both preprocedurally and in outpatient follow-up. It provides a noninvasive, high-resolution alternative to the current standard, transesophageal echocardiography, and may display advantages in both the detection and characterization of device-specific complications, such as peridevice leak and device-related thrombosis. The implementation of CCT in the follow-up after LAAO has identified new findings such as hypoattenuated thickening on the atrial device surface and left atrial appendage contrast patency, which are not readily assessable on transesophageal echocardiography. Currently, there is a lack of standardization for acquisition and interpretation of images and consensus on definitions of essential findings on CCT in the postprocedural phase. This paper intends to provide a practical and standardized approach to both acquisition and interpretation of CCT after LAAO based on a comprehensive review of the literature and expert consensus among European and North American interventional and imaging specialists.

Watchman vs. Amulet for Left Atrial Appendage Closure: Current Evidence and Future Perspectives

Left atrial appendage closure (LAAC) is a crucial intervention for stroke prevention in patients with non-valvular atrial fibrillation who are unsuitable for long-term anticoagulation. Amulet and Watchman are the most implanted devices worldwide for performing LAAC, and the aim of this review is to provide a comprehensive comparison focusing on their efficacy, safety, and short- and long-term outcomes. The Watchman device, the first to gain FDA approval, has been extensively studied and demonstrates significant reductions in stroke and systemic embolism rates. The Amulet device, a newer alternative, promises enhanced design features for more efficient appendage sealing. Current data highlight that both devices offer similar efficacy and safety for LAAC. While the two devices differ in terms of intraprocedural complication rates, they offer similar short- to long-term outcomes in terms of peri-device leaks, device-related thrombosis, and mortality. Both devices are indicated for patients who are unable to tolerate OAC, given their similar risk and safety profiles. Newer clinical studies are directed at establishing the efficacy of both devices as the primary method for stroke prevention in AF as an alternative to OAC.

Transition from WATCHMAN generation-2.5 device to WATCHMAN FLX device for percutaneous left atrial appendage closure: Incidence and predictors of device-related thrombosis and short- to mid-term outcomes

BACKGROUND

Patients with nonvalvular atrial fibrillation (AF) not suitable for long-term anticoagulant therapy undergo percutaneous left atrial appendage closure (LAAC) using the WATCHMAN device. The safety and efficacy of WATCHMAN-FLX (WM-FLX) compared with WATCHMAN-2.5 (WM-2.5), particularly in Asian populations, is unknown.

METHODS

We evaluated the background, procedure, and clinical outcomes of 199 patients who underwent LAAC between September 2019 and December 2022 and compared WM-2.5 (72 patients) with WM-FLX (127 patients).

RESULTS

The mean age was 76 years, with 128 men, and 100 had nonparoxysmal AF (non-PAF). The mean CHA2DS2-VASc, and HAS-BLED were 5.1, and 3.2 points, respectively. WM-FLX group demonstrated a shorter procedure time than WM-2.5 group (50 vs. 42 min, p = 0.001). The WM-FLX group demonstrated no procedural-related acute cardiac tamponade, which was significantly low (5.6% vs. 0%, p = 0.02), and a significantly higher rate of complete seal at 45-day (63% vs. 80%, p = 0.04). WM-FLX group had a significantly higher cumulative 1-year incidence of device-related thrombosis (DRT) than WM-2.5 group (3.4% vs. 7.0%, Log-rank p = 0.01). Univariate analysis identified two DRT risk factors in the WM-FLX group: non-PAF (odds ratio [OR] 7.72; 95% confidence interval [CI] 1.20-48.7; p = 0.04), and 35-mm device (OR 5.13; 95% CI 1.31-19.8; p = 0.02).

CONCLUSIONS

WM-FLX significantly improved the procedural quality and safety of LAAC. However, DRT remains an important issue even in the novel LAAC device, being a hazard for patients with high DRT risk, such as having non-PAF and using 35-mm devices.

Challenges and advances in device-related thrombus in left atrial appendage occlusion

Oral anticoagulation therapy (OAC) is a mainstay for mitigating stroke and other embolic events in patients with atrial fibrillation (AF). Despite the demonstrated efficacy of OAC in reducing events, many patients are unable to tolerate OAC due to bleeding risks. Left atrial appendage occlusion (LAAO) devices were developed as implantable technologies to moderate stroke risk in patients with intolerance to OAC. Despite clinical data supporting near-comparable protection against thromboembolic events with OAC, device-related thrombus formation has emerged as a critical complication following LAAO that remains a potential limitation to the safety and efficacy of LAAO. Improved biocompatibility of LAAO devices with fluoropolymers, a well-established stent-coating technology used to reduce thrombus formation and promote endothelialization, may optimize outcomes after LAAO.

Comparative Data of Procedural and Midterm Outcomes in Patients Who Underwent Percutaneous Left Atrial Appendage Closure Between the WATCHMAN FLX and WATCHMAN 2.5 Devices - Insight From the OCEAN-LAAC Registry

BACKGROUND

Limited data are available regarding clinical outcomes after percutaneous left atrial appendage closure using WATCHMAN FLX (WM-FLX) and WATCHMAN-2.5 (WM2.5) devices in Asian patients.

METHODS AND RESULTS

Data of 1,464 consecutive patients (WM-FLX, n=909; WM2.5, n=555) were extracted from a Japanese multicenter registry, and clinical data were compared between the 2 groups. No in-hospital deaths, periprocedural stroke, or device embolization occurred. Procedural success was significantly higher in the WM-FLX than WM2.5 group (95.8% vs. 91.9%; P=0.002) owing to the lower incidence of periprocedural pericardial effusion (0.55% vs. 1.8%; P=0.021). No significant differences in all-cause death, postprocedural stroke, and device-related thrombus were observed between the 2 groups. However, the cumulative bleeding rate at 1 year was substantially lower in the WM-FLX group (7.8% vs. 16.4%; P<0.001). Landmark analysis of bleeding events highlighted lower bleeding rates in the WM-FLX than WM2.5 group within the first 6 months (6.4% vs. 14.8%; P<0.001), with comparable bleeding rates over the 6- to 12-month period (1.5% vs. 3.2%, respectively; P=0.065).

CONCLUSIONS

This study demonstrated higher early safety and lower 1-year bleeding rates in the WM-FLX than WM2.5 group. The lower bleeding events with WM-FLX are likely due to multiple factors other than purely difference in devices, such as postprocedural drug regimen.

UV-Triggered Hydrogel Coating of the Double Network Polyelectrolytes for Enhanced Endothelialization

The left atrial appendage (LAA) occluder is an important medical device for closing the LAA and preventing stroke. The device-related thrombus (DRT) prevents the implantation of the occluder in exerting the desired therapeutic effect, which is primarily caused by the delayed endothelialization of the occluder. Functional coatings are an effective strategy for accelerating the endothelialization of occluders. However, the occluder surface area is particularly large and structurally complex, and the device is subjected to a large shear friction in the sheath during implantation, which poses a significant challenge to the coating. Herein, a hydrogel coating by the in situ UV-triggered polymerization of double-network polyelectrolytes is reported. The findings reveal that the double network and electrostatic interactions between the networks resulted in excellent mechanical properties of the hydrogel coating. The sulfonate and Arg-Gly-Asp (RGD) groups in the coating promoted hemocompatibility and endothelial growth of the occluder, respectively. The coating significantly accelerated the endothelialization of the LAA occluder in a canine model is further demonstrated. This study has potential clinical benefits in reducing both the incidence of DRT and the postoperative anticoagulant course for LAA closure.

Left atrial appendage closure for patients with atrial fibrillation at high intracranial haemorrhagic risk

BACKGROUND AND OBJECTIVES

Although left atrial appendage closure (LAAC) is performed in patients with non-valvular atrial fibrillation (NVAF) at increased risk of intracranial haemorrhage (ICH), outcome data are scarce. We assessed the detailed neurological indications for LAAC and outcomes after LAAC in high ICH risk patients.

METHODS

Study population included consecutive patients with NVAF who underwent LAAC in a single hospital network between January 2015 and October 2021 because of prior ICH or the presence of high ICH risk imaging markers on brain MRI (cerebral microbleeds (CMBs)). Primary safety and efficacy outcome measures were the occurrence of ICH and thromboembolic events, respectively, after LAAC.

RESULTS

Among 146 patients with NVAF who underwent LAAC for high ICH risk, 122 had a history of ICH, while 24 presented with high ICH risk imaging markers only. Mean age was 75.7±7.61, 42 (28.8%) were women. Mean CHA2DS2-VASc score was 5.23±1.52. Of 122 patients with ICH history, 58 (47.5%) had intraparenchymal haemorrhage (IPH), 40 (32.8%) had traumatic ICH (T-ICH) and 18 (14.7%) had non-traumatic subdural haemorrhage. Of 85 patients with brain MRIs including necessary sequences, 43 (50.6%) were related to cerebral amyloid angiopathy and 37 (43.5%) to hypertensive microangiopathy. While 70% of patients were discharged on oral anticoagulants (OAC), 92% were not taking OAC at 1 year. Over 2.12 years mean follow-up, one patient had recurrent non-traumatic IPH (incidence rate (IR) 0.32 per 100 patient-years), five had T-ICH (IR 1.61 per 100 patient-years) and six had an ischaemic stroke (IR 1.94 per 100 patient-years).

CONCLUSIONS

Among patients with NVAF at high ICH risk, LAAC demonstrated a low risk of recurrent ICH or ischaemic stroke compared with previously published data. LAAC in high ICH risk populations should be considered in clinical practice per FDA approval and recent guidelines.

First-in-human left atrial appendage closure using the WATCHMAN FLX Pro device: a case report

Background

Device-related thrombosis (DRT) is a known complication to left atrial appendage closure (LAAC). The surface of a LAAC device should ideally have antithrombotic properties. The novel WATCHMAN FLX Pro (WFP) incorporates a fluoropolymer-coated fabric membrane designed to increase thromboresistance and facilitate endothelialization. Such features could potentially allow for a minimal post-procedural antithrombotic regimen. Radiopaque platinum markers at the device shoulders and a large 40 mm device are other novel features of the WFP.

Case summary

A 75-year-old man with atrial fibrillation was referred for LAAC due to prior subdural haemorrhage during direct-acting anticoagulation treatment. He underwent the first-in-human WFP implantation as part of the WATCHMAN FLX Pro CT study (NCT05567172). Computed tomography (CT) was used for pre-planning, and the procedure was performed under local analgesia guided by intracardiac echocardiography from the left atrium (LA) without any complications. Post-procedural antithrombotic treatment consisted of acetylsalicylic acid 75 mg/day only, and 45-day CT, transoesophageal echocardiography (TEE), and magnetic resonance imaging demonstrated optimal device position with complete LAAC. Hypoattenuated thickening (6 mm) appeared on the device as a smooth surface in continuity with the left atrial wall on CT and TEE. A specific magnetic resonance T1-weighted scan, used for visualization of fresh thrombus, suggested this to represent tissue ingrowth rather than thrombus.

Discussion

The advanced follow-up imaging protocol suggested a good WFP implantation result with signs of tissue ingrowth at 45 days. The added radiopaque markers facilitated optimal deployment, evaluation of device stability during tug test, and assessment of device protrusion into the LA.

State-of-the-Art of Transcatheter Left Atrial Appendage Occlusion

Left atrial appendage occlusion (LAAO) is an increasingly used alternative to oral anticoagulation in patients with atrial fibrillation, especially in patients with absolute/relative contraindications to these therapies. This review will cover three main aspects of the procedure. In the fist part of the manuscript, we focus on patient selection. We describe three main categories of patients with primary indication to LAAO, namely patients with previous or at a high risk of intracerebral bleeding, patients with a history of major gastrointestinal bleeding and patients with end-stage renal disease and absolute contraindication to novel oral anticoagulants. Some other potential indications are also described. In the second part of the manuscript, we review available devices, trying to highlight different aspects and potential specific advantages. The last section overviews different ways for pre-, intra- and postprocedural imaging, in order to improve procedural safety and efficacy and ameliorate patient outcome. The characteristics of available contemporary devices and the role of imaging in procedural planning, intraprocedural guidance and follow-up are described.

Left Atrial Appendage Occlusion and Post-procedural Antithrombotic Management

Left atrial appendage occlusion (LAAO) is an established alternative to oral anticoagulation for stroke prevention in atrial fibrillation. Antithrombotic therapy is used in the post-procedural period to prevent device-related thrombosis (DRT). The risk of DRT is considered highest in the first 45-90 days after device implantation, based on animal studies of the device healing process. Clinically applied antithrombotic regimens vary greatly across studies, continents, and centers. This article gives an overview of the evidence behind current antithrombotic regimens, ongoing randomized trials, and future post-procedural management.

Pattern of Endothelialization in Left Atrial Appendage Occluder by Optic Coherence Tomography: A Pilot Study

BACKGROUND

Implantation of the left atrial appendage occluder (LAAO) has been proven to prevent stroke effectively in patients with atrial fibrillation who cannot tolerate anticoagulants. Incomplete endothelization of LAAO may cause device-related thrombus, and currently no good image modality exists to clearly see LAAO endothelialization. We aimed to use coronary optic coherence tomography (OCT) to visualize LAAO endothelialization.

METHODS AND RESULTS

We enrolled 14 patients (72.8±9.4 years old) undergoing pulmonary vein isolation with a preexisting LAAO implanted more than 1 year ago (5 Watchman and 9 Amulet). After pulmonary vein isolation, we did OCT via steerable sheath and coronary guiding catheter to adjust OCT probe location and injected contrast medium to visualize the LAAO surface. In vitro testing was also performed to see the bare occluder. In vitro OCT showed the surface of the bare device as an interrupted granule pattern, which included the Watchman surface polytetrafluoroethylene membrane string, Amulet disc metal strut, and inner polytetrafluoroethylene membrane string. In the implanted Watchman, OCT showed endothelialization as a smooth surface layer with noninterrupted coarser granules. In the implanted Amulet, OCT showed endothelialization as thin (early) or thick (late) endothelialization layer covering struts with OCT shadows. Among patients with Watchman, 2 showed no, 2 early, and 1 complete endothelialization. Among patients with Amulet, 2 showed no, 3 early, and 4 late endothelialization.

CONCLUSIONS

We demonstrated the feasibility of OCT to visualize LAAO endothelization with high resolution. Further studies are needed to determine antithrombotic regimens if incomplete endothelization is detected. A new OCT catheter may be designed specifically for LAAO.