Left Atrial Appendage Closure and Atrial Fibrillation

In valvular atrial fibrillation (AF), thrombus formation may occur:

in the left atrial appendage (60 %), or
in other parts of the atria (40 %).

In valvular AF:

percutaneous occlusion with an occluder is not recommended, because up to 40 % of thrombi form outside the appendage.
surgical closure is recommended during another cardiac surgery (e.g. mitral valve replacement).

However, cardiac surgery solely for appendage closure is not recommended.

In non-valvular AF, thrombus formation may occur:

in the left atrial appendage (90 %), or
in other parts of the atria (10 %).

The trigger for AF is most commonly located:

in the region of the pulmonary vein ostia (95 %)
in the left atrial appendage (5 %)

27 % of patients with recurrent AF after ablation or with AF refractory to medical therapy

have the AF trigger located in the left atrial appendage.

If long-term anticoagulation therapy is contraindicated in a patient with AF,

left atrial appendage closure may be considered for thromboembolism prevention.
The appendage is closed percutaneously using an occluder (Watchman),

or surgically (as an adjunctive cardiac surgical procedure).

Illustration depicting left atrial appendage closure using Watchman and Amplatzer Amulet occlusion devices as an alternative strategy for thromboembolism prevention in atrial fibrillation.

Function of the left atrial appendage:

Haemodynamic function:
- An elastic, decompression chamber with high compliance that reduces atrial pressure during volume overload.
- Contracts during atrial systole.
Hormonal production:

Primary site of synthesis and release of ANP (atrial natriuretic peptide), which regulates blood pressure via diuresis.

Mechanoreceptors:

Sensors in the appendage wall monitor atrial pressure.

Percutaneous Left Atrial Appendage Occlusion (Indications)
Spontaneous major bleeding from an irreversible source: gastrointestinal (melena, haematemesis, haemorrhage), genitourinary (haematuria), respiratory (haemoptysis), retroperitoneal, pericardial, intracranial, intraspinal, haemarthrosis (bleeding into joints), intraocular (retinal)
Spontaneous major bleeding due to irreversible: thrombocytopenia, coagulopathy
Recurrent major bleeding due to unavoidable falls.
Intolerance to anticoagulation therapy
Low compliance (patient does not take anticoagulation therapy)

Illustration depicting left atrial appendage closure using percutaneous devices Watchman, Watchman FLX, ACP, Amplatzer Amulet, LAMBRE and Omega, as well as surgical systems AtriClip and PendiTure, for thromboembolism prevention in patients with atrial fibrillation.

After appendage closure using an occluder (e.g. Watchman), patients must continue for 6 months:

dual antithrombotic therapy (e.g. NOAC and aspirin) or dual antiplatelet therapy (clopidogrel and aspirin)
and thereafter lifelong aspirin.

Percutaneous Left Atrial Appendage Occlusion (Contraindications)
Inability to administer short-term anticoagulation or antiplatelet therapy
Thrombus in the atria or ventricles.
Valvular atrial fibrillation
Allergy to occluder material (nitinol, nickel, titanium)

Left atrial appendage closure in AF with CHA₂DS₂-VA score ≥ 2

leads to a 33 % reduction in thromboembolism.

Anticoagulation therapy after surgical closure remains indicated because thrombi may also form outside the appendage.

In the future, discontinuation may be considered if contraindications to anticoagulation therapy arise.

The left atrial appendage can be closed in 3 ways:

Percutaneously:

occlusion (e.g. Watchman, Amplatzer)

Surgically:

exclusion (e.g. AtriaClip, stapler)
excision (amputation and suture)

Occlusion (percutaneous appendage closure)

is percutaneous closure of the left atrial appendage ostium,
performed from the endocardial side, inside the left atrium,
an occluder (Watchman, Amplatzer) is deployed into the appendage ostium.

Exclusion (surgical appendage closure)

is surgical closure of the left atrial appendage ostium,
performed from the epicardial side, on the external surface of the left atrium during cardiac surgery,
a clip (AtriaClip) is applied to the ostium or it is closed with a stapler.

Excision (surgical removal of the appendage)

is a cardiac surgical procedure involving resection (amputation) of the appendage followed by suture of the opening,
performed from the epicardial side during cardiac surgery.

Left Atrial Appendage Occlusion
Situation	When to close the appendage	Method	Post-procedural therapy
Valvular AF (mitral stenosis, mechanical valve)	Only during concomitant cardiac surgery, never as a standalone procedure	Surgical	Warfarin (lifelong)
Non-valvular AF with contraindication to anticoagulation therapy	Appendage closure may be considered to reduce embolic risk	Percutaneous occluder (Watchman, Amplatzer)	6 months dual therapy → then lifelong aspirin
Non-valvular AF during cardiac surgery	As an adjunct during planned surgery	Surgical	Anticoagulation therapy according to CHA₂DS₂-VA

Percutaneous left atrial appendage occlusion is an invasive procedure associated with a complication rate of approximately 2–4 %.

In very frail patients at high bleeding risk, the benefit may not outweigh the procedural risk.
Most common complications:

Pericardial tamponade
Stroke or TIA (air embolism or thromboembolism)
Occluder dislocation
Occluder thrombosis
Residual leak
Vascular access site complications

Percutaneous Left Atrial Appendage Occlusion	Class
In patients with non-valvular AF and CHA₂DS₂-VA ≥ 2 who have a contraindication to long-term anticoagulation therapy, percutaneous left atrial appendage occlusion may be considered.	IIa
In non-valvular AF (low bleeding risk) after percutaneous left atrial appendage occlusion (Watchman FLX), anticoagulation therapy is discontinued after 45 days (if no >5 mm leak is present on transoesophageal echocardiography).	I
In non-valvular AF after percutaneous left atrial appendage occlusion, long-term aspirin therapy is recommended.	I

Surgical Left Atrial Appendage Closure	Class
Surgical left atrial appendage closure is recommended (as adjunctive “anticoagulation” therapy) in all patients with AF undergoing cardiac surgery.	I
Thoracoscopic surgical left atrial appendage closure may be considered in patients with a contraindication to long-term anticoagulation therapy who are unsuitable for percutaneous appendage closure.	IIb
In non-valvular AF after surgical left atrial appendage closure, anticoagulation therapy is indicated according to the CHA₂DS₂-VA score.	I
In valvular AF after surgical left atrial appendage closure, warfarin is administered regardless of the CHA₂DS₂-VA score.	I

Diagram illustrating antithrombotic therapy after Watchman FLX implantation, including strategies with NOACs, warfarin, clopidogrel, and aspirin according to bleeding and thrombotic risk over a 6-month period.

Diagram illustrating antithrombotic therapy after implantation of ACP and Amplatzer Amulet devices with clopidogrel and aspirin administration over a defined period of up to 6 months.

In patients after left atrial appendage occlusion or after percutaneous coronary intervention (PCI)

bleeding risk is assessed using the ARC-HBR (Academic Research Consortium – High Bleeding Risk) score.
The ARC-HBR score is positive if the patient has ≥1 major criterion or ≥2 minor criteria.

ARC-HBR Score (Bleeding Risk)

Major criteria (1 is sufficient)

Active bleeding
Previous intracranial bleeding
Intracranial tumour or arteriovenous malformation
Recent intracranial event (<6 months)
Long-term oral anticoagulation (NOAC or Warfarin)
Thrombocytopenia <100 × 10⁹/l
Haemoglobin <11 g/dl or transfusion within the last 4 weeks
Severe chronic kidney disease (eGFR <30 ml/min)
Severe liver disease with portal hypertension

Minor criteria (≥2 required)

Age ≥75 years
Mild to moderate chronic kidney disease (eGFR 30–59 ml/min)
Haemoglobin: men 11–12.9 g/dl, women 11–11.9 g/dl
Chronic treatment with steroids or NSAIDs:
- ibuprofen, diclofenac, naproxen, indomethacin, ketorolac
History of non-intracranial bleeding (>12 months)

ARC-HBR - Academic Research Consortium – High Bleeding Risk. PCI - Percutaneous Coronary Intervention. NOAC – Non-vitamin K Oral Anticoagulant (Dabigatran, Rivaroxaban, Apixaban, Edoxaban). eGFR = estimated Glomerular Filtration Rate. NSAIDs - non-steroidal anti-inflammatory drugs

Low bleeding risk in patients after left atrial appendage occlusion is assessed according to the following table.

Low Bleeding Risk (after left atrial appendage occlusion)
All criteria must be fulfilled
HAS-BLED < 3
ARC-HBR: no major criterion and ≤ 1 minor criterion
No previous life-threatening bleeding
Stable anticoagulation therapy in the past without complications
Normal renal function (CrCl > 50 ml/min)
Normal liver function
No active gastrointestinal ulceration
No recent surgery or traumatic events
No anaemia or thrombocytopenia
No need for dual antiplatelet therapy (DAPT) for another indication

DAPT - Dual Antiplatelet Therapy (Aspirin + Clopidogrel). CrCl – creatinine clearance

High thrombotic risk in patients after left atrial appendage occlusion is assessed according to the following table.

High Thrombotic Risk (after left atrial appendage occlusion)
One parameter is sufficient
CHA₂DS₂-VA ≥ 5
Previous appendage thrombus
Thrombophilias (factor V Leiden, protein C/S deficiency, antiphospholipid syndrome)
Left atrial dilatation (>50 mm, LAVI >40 ml/m²)
Persistent atrial fibrillation
Left ventricular ejection fraction (<40 %)
Spontaneous echocontrast in the left atrium
History of embolization during anticoagulation therapy
Obesity + diabetes + hypertension + age >75 years (synergistic effect)