Left Atrial Appendage Occlusion

Understanding the Left Atrial Appendage (LAA)

The left atrial appendage (LAA) is a muscular sac in the left atrium of the heart. In patients with atrial fibrillation (AFib), the atrium does not contract effectively, leading to blood stasis. This pooling of blood within the appendage creates a high risk for thrombus (clot) formation, which may embolize and cause ischemic stroke.

Studies show that in non-valvular atrial fibrillation, over 90% of atrial thrombi originate in the LAA. This makes the appendage a central target for stroke prevention strategies.

Why Consider LAA Closure or Occlusion?

The standard prevention strategy for AFib patients is long-term oral anticoagulation (warfarin or direct oral anticoagulants). However, many patients are not ideal candidates due to:

• High bleeding risk (e.g., prior gastrointestinal or intracranial bleeding)
• Difficulty maintaining therapeutic international normalized ratio, INR (warfarin)
• Contraindications to anticoagulation (frequent falls, frailty, comorbidities)

For these patients, mechanical exclusion of the LAA, through LAA closure (LAAO) or occlusion procedures, is an effective alternative to reduce stroke risk.

Techniques for LAA Closure and Occlusion

Several strategies are used in clinical practice, depending on patient anatomy, risk profile, and coexisting cardiac disease:

• Percutaneous LAA closure
  A minimally invasive, catheter-based approach performed via transseptal puncture. The most widely used method worldwide.
• Surgical closure
  Typically performed during open-heart surgery (e.g., mitral valve replacement or coronary bypass). Closure can be achieved through suturing, stapling, or the use of surgical clip devices, such as the AtriClip.
• Hybrid approaches
  Combine surgical and percutaneous techniques in select patients.

LAA Closure Devices

A wide range of dedicated devices is available for percutaneous and surgical LAA closure, each designed to accommodate different appendage anatomies:

WATCHMAN FLX™ (Boston Scientific)

The WATCHMAN FLX is a catheter-delivered device intended to reduce stroke risk in patients with nonvalvular atrial fibrillation who are eligible for anticoagulation. It has a self-expanding nitinol frame covered with a porous PET membrane that seals the LAA opening. The device can be fully recaptured and repositioned during implantation, providing flexibility for optimal placement and long-term stability.

Amplatzer™ Amulet™ (Abbott)

The Amulet device features a dual-component design with a distal lobe that anchors inside the LAA and a proximal disc that seals the ostium. This configuration allows the device to conform to a range of appendage shapes, providing secure closure for anatomies that may be shallow or multi-lobed.

LAAmbre™ (Lifetech Scientific)

The LAAmbre system consists of a distal umbrella and a proximal cover connected by a short central waist. Its flexible design accommodates different ostium sizes and depths, allowing effective sealing and stable anchoring across variable LAA anatomies.

AtriClip® (AtriCure)

The AtriClip is a surgical device applied externally at the base of the LAA during cardiac surgery. By completely excluding the appendage from the circulation, it eliminates blood flow into the LAA and electrically isolates it from the left atrium.

Lariat® (SentreHEART)

The Lariat device uses a combined endocardial–epicardial approach to deliver a pre-tied suture around the LAA base. This method closes the appendage without leaving any device inside the heart, making it an option for patients who cannot receive endocardial implants.

Role of Imaging in LAA Closure Planning

Pre-procedural imaging is essential for successful LAA closure, as it guides device selection, sizing, and procedural strategy. Both cardiac CT and 3D transesophageal echocardiography (3D TEE) are widely used for planning, each offering unique advantages.

CT Planning

Cardiac CT provides a comprehensive 3D view of the LAA anatomy, enabling detailed assessment of:
• Ostium size and shape
• Landing zone dimensions and depth
• Lobe number and orientation
• Relationship to the left circumflex artery and pulmonary veins

CT-derived reconstructions support virtual device sizing and trajectory simulation.

3D TEE Planning

3D TEE is the standard intra-procedural imaging modality, and in many centers, it is also used pre-procedurally for planning. It allows real-time visualization of the LAA, measurement of landing zones, and detection of thrombus without the need for contrast or radiation exposure.

3D TEE offers excellent spatial and temporal resolution for guiding transseptal puncture, device deployment, and confirmation of seal integrity during the procedure.

CT vs. 3D TEE

While CT offers superior spatial resolution and reproducibility for complex anatomies, 3D TEE provides real-time dynamic imaging that can be used both before and during the intervention. Many centers now adopt a multimodality approach, combining both modalities for comprehensive evaluation and optimal device selection.

Clinical Impact of LAA Closure

For properly selected patients, LAA occlusion reduces stroke risk, lowers bleeding risk compared to chronic anticoagulation, and improves long-term outcomes. Importantly, closure is not universally recommended for all AFib patients, those who can safely remain on anticoagulants often continue with medical therapy.

Key Takeaways:

• The LAA is the primary source of clot formation in AFib.
• Closure and occlusion procedures provide alternatives for patients who cannot use long-term anticoagulation.
• Watchman and Amulet are the leading percutaneous devices, with complementary strengths.
• Other devices (AtriClip, Lariat, Lambre) broaden treatment options.
• Guidelines support LAA closure in high-risk, anticoagulation-intolerant patients.