Condition category
Circulatory System
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status

Plain English Summary

Background and study aims
Atrial fibrillation (AF) is a common heart condition, affecting millions of people worldwide. The heart consists of two upper chambers (atria) and two lower chambers (ventricles). Inside the right atrium, a cluster of cells (sinus node) are responsible for firing electrical signals into the heart muscle causing the heart to beat regularly (sinus rhythm). When a person is suffering from AF, the normal signals from the sinus node do not work properly, causing other parts of the atria to fire chaotically. These uncoordinated signals cause the heart to beat irregularly and often very fast (arrhythmia). People suffering from AF have a much higher risk of developing other problems, such as stroke. Prevention of stroke in people with AF is usually achieved using blood thinning medications such as colchicine however this is not always effective and there is a risk of serious bleeding. The left atrial appendage is a small structure in the muscle wall of the left atrium and is thought to be the most common source of blood clots causing stroke in patients with AF. Left atrial appendage closure (LAAC) is a treatment strategy which has been an area of interest in the field of stroke prevention. Blocking off (occluding) this structure during surgery using a suture (stitch) or surgical stapler, could be an effective method of stroke prevention in these patients, removing the need to take blood thinners. The aim of this study is to find out whether left atrial appendage occlusion can help to lower the occurrence of stroke in AF patients.

Who can participate?
Adults with AF who are having heart surgery involving a cardiopulmonary bypass.

What does the study involve?
Participants are randomly allocated to one of two groups. For those in the first group, during their surgery, the surgeon will block off (occlude) the left atrial appendage using a suture (stitch) and/or surgical stapler. For those in the second group, the left atrial appendage is not closed during surgery. Participants in both groups are followed up in order to find out which group has the higher occurrence of stroke.

What are the possible benefits and risks of participating?
Not provided at time of registration.

Where is the study run from?
Hammersmith Hospital (UK)

When is the study starting and how long is it expected to run for?
November 2015 to December 2017

Who is funding the study?
Canadian Institutes for Health Research (UK)

Who is the main contact?
1. Mr Sajiram Sarvananthan (public)
2. Mr Prakash Punjabi (scientific)

Trial website

Contact information



Primary contact

Mr Sajiram Sarvananthan


Contact details

Imperial College Healthcare NHS Trust
Hammersmith Hospital
Du Cane Road
W12 0HS
United Kingdom
+44 7949 554467



Additional contact

Mr Prakash Punjabi


Contact details

Hammersmith Hospital
Department Of Cardiothoracic Surgery
Du Cane Road
W12 0HS
United Kingdom
+44 208 383 2026

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

Left Atrial Appendage Occlusion Study III (LAAOS III)


Study hypothesis

The aim of this study is to examine the impact of left atrial appendage occlusion on the incidence of stroke or systemic arterial embolism in patients with atrial fibrillation undergoing cardiac surgery over the duration of follow ­up.

Ethics approval


Study design

Randomised controlled trial

Primary study design


Secondary study design

Randomised controlled trial

Trial setting


Trial type


Patient information sheet

Not available in web format, please use the contact details below to request a patient information sheet


Topic: Cardiovascular; Subtopic: Cardiovascular (all Subtopics); Disease: Cardiac Surgery


Participants are randomly allocated to one of two groups.

Intervention group: Surgeon will occlude the left atrial appendage using a suture and/or a surgical stapler or a regulatory approved atrial appendage closure during the patient's cardiac surgery procedure.

Control group: Surgeon will not close the left atrial appendage during the patient's cardiac surgery procedure.

Intervention type



Phase III

Drug names

Primary outcome measures

First occurrence of stroke or systemic arterial embolism over the duration of follow-up.

Secondary outcome measures

Not provided at time of registration

Overall trial start date


Overall trial end date


Reason abandoned


Participant inclusion criteria

1. Aged 18 years or above
2. Undergoing a clinically indicated cardiac surgical procedure with the use of cardiopulmonary bypass
3. A documented history of atrial fibrillation or atrial flutter
4. CHA2DS2-­VASc score ≥ 2
5. Written informed consent

Participant type


Age group




Target number of participants

Planned Sample Size: 4700; UK Sample Size: 200

Participant exclusion criteria

1. Patients undergoing any of the following procedures:
1.1. Off­-pump cardiac surgery
1.2. Heart transplant
1.3. Complex congenital heart surgery
1.4. Sole indication for surgery is ventricular assist device insertion
1.5. Previous cardiac surgery (re­operation)
1.6. Mechanical valve implantation
2. Patients who have had a previous placement of a percutaneous LAA closure device

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

Hammersmith Hospital
Imperial College Healthcare NHS Trust Du Cane Road
W12 0HS
United Kingdom

Sponsor information


Imperial College Healthcare NHS Trust

Sponsor details

Hammersmith Hospital
Du Cane Road
W12 0HS
United Kingdom

Sponsor type

Hospital/treatment centre



Funder type


Funder name

Canadian Institutes of Health Research

Alternative name(s)

Instituts de Recherche en Santé du Canada, CIHR

Funding Body Type

government organisation

Funding Body Subtype

Federal/National Government



Results and Publications

Publication and dissemination plan

Not provided at time of registration

Intention to publish date

Participant level data

Not provided at time of registration

Results - basic reporting

Publication summary

Publication citations

Additional files

Editorial Notes

24/06/2016: Mr Prakash P Punjabi has been added as a study contact.