Preclinical assessment of a modified Occlutech left atrial appendage closure device in a canine model

Preclinical Assessment of a Novel Conformable Foam-Based Left Atrial Appendage Closure Device

Background

Left atrial appendage (LAA) occlusion has been established as an alternative to systemic anticoagulation for stroke prevention in patients with atrial fibrillation; however, limitations of current devices have slowed adoption. We present preclinical evaluations of a novel device, the Conformal Left Atrial Appendage Seal (CLAAS).

Methods

An in vitro assessment of conformability was conducted to evaluate the two CLAAS devices (regular 27 mm and large 35 mm) and a Watchman 2.5 (27 mm). Devices were placed within silicone tubes and compressed in a vise submerged in a water bath at 37°C. Changes in device diameter and visual seal were noted. Acute (n = 1) and chronic 60-day (n = 6) canine studies with gross and histologic assessment were performed.

Results

Conformability bench tests demonstrated that the regular CLAAS implant was able to seal oval orifices from 20 × 30 mm to 15 × 33 mm and the large from 30 × 35 mm to 20 × 40 mm. As the CLAAS implant was compressed in the minor diameter, it increased in the major diameter, thereby filling the oval space, whereas the Watchman 2.5 showed gaps and maintained its round configuration when compressed in one direction. Seven devices were successfully implanted in the canine model with complete seal without thrombus. Histologic examination showed complete neointima covering with minimal inflammation at 60 days.

Conclusions

Preclinical testing demonstrated the conformability of the CLAAS implant and its ability to seal the LAA. Clinical studies are ongoing to characterize the utility of the CLAAS implant in the treatment of patients with atrial fibrillation.

State-of-the-art preclinical testing of the OMEGATM left atrial appendage occluder

OBJECTIVES

This study aimed to present a new approach of thorough preclinical testing of a novel left atrial appendage (LAA) occluder device.

BACKGROUND

The development of a safe and effective LAA occluder has been shown to be challenging.

METHODS

The novel OMEGATM LAA occluder (Eclipse Medical, Ireland) was tested in a porcine model and three-dimensional (3D) human LAA models - this as a prelude to its first-in-human use.

RESULTS

In a first series of in-vivo experiments, the OMEGATM LAA occluder was shown to have a satisfactory device biocompatibility in a porcine model. The design of the OMEGATM device was further refined and optimized following three more series of in-vivo experiments. The second generation OMEGATM device was designed with thinner wires, leading to a profile reduction. Based on in-vitro testing of different OMEGATM device sizes implanted at different depths in human three-dimensional (3D) LAA models, it could be determined that (1) the landing zone should be measured at a median depth of 12 mm from the LAA ostium; (2) the distal self-retaining inverted cup should have 10%-25% compression to minimize device embolization risk; and (3) the disc should be slightly inverted, i.e. pulled into the LAA, to promote complete LAA occlusion. The combined in-vivo and in-vitro testing resulted in an optimized pre-procedural planning of the first-in-human case treated with the OMEGATM device.

CONCLUSIONS

This series of carefully planned in-vivo and in-vitro experiments allowed demonstration of the safety and efficacy of the OMEGATM LAA occluder. This approach of thorough preclinical testing of medical devices may reduce the risk of complications in first-in-human cases and may become the standard approach for device development and preclinical testing in the future.

Preclinical assessment of a modified Occlutech left atrial appendage closure device in a porcine model

Left atrial appendage (LAA) closure is being developed as an alternative for stroke prevention in patients with atrial fibrillation that cannot tolerate long-term oral anticoagulation. To assess the feasibility, safety, and performance of a novel modified Occlutech LAA closure device in a preclinical porcine model, the modified Occlutech modified Occlutech Plus LAA closure device was implanted in 12 female pigs (25-39 kg body weight) under fluoroscopic and transesophageal echocardiography (TEE) guidance. Procedural and technical success, as well as safety of LAA closure, were evaluated peri-procedurally and after 4, 8, and 12 weeks. Moreover, after 4, 8 and, 12 weeks animals were sacrificed for pathological analysis (e.g., thrombus formation, device ingrowth, endothelialization, and inflammation). All LAA closure devices were successfully implanted. On follow-up, no serious adverse events such as device-associated thrombus or translocalization/embolization were observed. A clinically non-significant pericarditis was observed in 4 animals at the time of autopsy. Endothelialization of the device was visible after 4 weeks, advanced after 8 weeks and completed after 12 weeks. Immunohistochemistry showed low amounts of inflammatory infiltration on the edges of the device. The results of this study indicate that implantation of a modified Occlutech LAA closure device is feasible with rapid endothelialization and low inflammatory infiltration in a porcine model. Human data are needed to further characterize safety and efficacy.

Plugs for left atrial appendage occlusion: an overview of available devices

INTRODUCTION

Approximately one-third of all ischemic strokes and the ensuing health and economic burden can be attributed to the presence of atrial fibrillation (AF). The global prevalence of AF continues to rise, thus making it by far the most common diagnosed cardiac arrhythmia. Percutaneous left atrial appendage (LAA) occlusion or obliteration has been developed to protect from the occurrence of stroke in patients with nonvalvular AF.

AREAS COVERED

We address the characteristics and techniques for implantation as well as some clinical registries and randomized trials of the various catheter-based devices for the occlusion of the LAA that are either currently available or in the clinical evaluation stage.

EXPERT OPINION

Over less than 2 decades, LAA occlusion progressed from being a concept applied in a few specialized centers to a globally recognized procedure implemented in numerous hospitals as part of daily interventional practice. The respective devices are to date safer and easier to deploy than initially. Periprocedural and postprocedural complications will continue to decrease as already evident from prospective randomized trials and registries. Although current indications focus on patients with nonvalvular AF and contraindications for oral anticoagulation, it is all but certain that the future will bring a widening in the spectrum of indications, applicability, and usage of these devices.

The WATCHMAN left atrial appendage closure device for patients with atrial fibrillation: current status and future perspectives

INTRODUCTION

Atrial fibrillation (AF) is associated with an increased risk of stroke. Stroke prevention with oral anticoagulation (OAC) is recommended in AF patients at increased risk of stroke. The left atrial appendage (LAA) is the main source of thrombus formation in AF patients. The WATCHMAN percutaneous LAA closure (LAAC) device may serve as an alternative to OAC overcoming disadvantages including the risk of (major) bleeding.

AREAS COVERED

This review will focus on LAAC with the Watchman device for stroke prevention in AF patients. Current status, available literature, clinical safety and efficacy will be summarized. Furthermore, the future perspectives of Watchman will be discussed.

EXPERT OPINION

LAAC with Watchman appears a promising, safe, and effective alternative to OAC. Ongoing and future studies to consolidate the position of Watchman should focus on comparative safety and efficacy of different LAAC devices, patient selection, various post-procedural antithrombotic regimens, head-to-head comparisons with NOAC, better understanding of device-related thrombus, and the role of the LAA in the propagation of non-valvular AF. This research may attribute to a paradigm shift in which LAAC no longer serves as a 'last resort' treatment for AF patients ineligible for OAC but may serve as a second-line or even first-line treatment option for AF patients.

Left Atrial Appendage Occlusion: The Current Device Landscape and Future Perspectives

Since the first percutaneous left atrial appendage occlusion (LAAO), many studies have shown the safety and efficacy of this technique to prevent embolic strokes in nonvavular atrial fibrillation. The design, characteristics, and clinical data of the most frequently used devices for LAAO are reviewed, including the Amplatzer cardiac plug and Amulet (Abbott Vascular), the Watchman (Boston Scientific), and the LARIAT device (SentreHEART). Similarly, newer closer devices, such as Ultraseal (Cardia), LAmbre (Lifetech), and Coherex WaveCrest (Johnson & Johnson), are also discussed. Finally, new technologies still in the stage of preclinical study or in the initial clinical experience are also reviewed.

Left Atrial Appendage Occlusion: What Are the Options and Where is the Evidence?

Left atrial appendage occlusion (LAAO) has emerged as an effective site-directed therapy in patients with nonvalvular atrial fibrillation (AF) for stroke prevention, who are ineligible for long-term oral anticoagulation. The objective of this study was to assess the safety, efficacy, and availability of LAAO devices by reviewing the literature and to review the development and effectiveness of LAAO by the transcatheter approach with plugging devices such as WATCHMAN™ (Boston Scientific, Natick, MA, USA); AMPLATZER™ Cardiac Plug and AMPLATZER™ Amulet™ (Abbott Laboratories, Chicago, IL, USA); and the LARIAT^® Suture Delivery Device (SentreHEART, Redwood City, CA, USA), which features an entirely unique hybrid (endocardial and epicardial) approach in closing the left atrial appendage (LAA). The conducted literature review ultimately revealed a substantial body of literature supporting the safety and efficacy of various LAAO strategies, including endocardial, epicardial, and hybrid approaches, in AF patients who are not eligible for long-term oral anticoagulant use. Specifically, the most attractive population suitable for LAA closure appears to be patients at high risk for ischemic stroke with a longer life expectancy but a moderate-to-high bleeding risk with long-term oral anticoagulation. The benefit of LAA closure in reducing the incidence of stroke in patients with nonvalvular AF has been evolving gradually, and we are confident that this new field of percutaneous LAA closure will continue to emerge as a game-changer in the treatment of AF.

Five years of keeping a watch on the left atrial appendage-how has the WATCHMAN fared?

Left atrial appendage closure (LAAC) is a promising site-directed therapy for stroke prevention in patients with non-valvular atrial fibrillation (AF) who are ineligible or contraindicated for long-term oral anticoagulation. A variety of LAAC modalities are available, including percutaneous endocardial occluder devices such as WATCHMAN^TM (Boston Scientific Corp., Marlborough, MA, USA), and an ever-increasing body of evidence is helping to define the optimal use of each technique. Similarly increased experience with LAAC has revealed challenges such as device-related thrombi and peri-device leaks for which the long-term significance and appropriate management are areas of active investigation. We review the evolution and long-term outcomes with the WATCHMAN^TM device with particular emphasis on the nuances of its use and its role in the broader landscape of appendageology.