Condition category
Circulatory System
Date applied
Date assigned
Last edited
Prospectively registered
Overall trial status
Recruitment status
Not yet recruiting

Plain English Summary

Background and study aims
The normal heart rhythm depends on the regular electrical activity of the heart’s natural pacemaker cells – the sinus node. The sinus node is in the right upper chamber of the heart and usually ‘fires’ at about 60-100 beats per minute but it can be faster (during exercise, for example). The electrical impulse spreads through the heart to create a coordinated contraction between the upper and lower chambers. In atrial fibrillation (AF), the normal rhythm is lost due to abnormal electrical activity from an area around the pulmonary veins. This results in a chaotic rhythm in the upper chambers of the heart which stops them from contracting effectively. As the electrical impulse is transmitted to the lower chambers it causes the heart to beat in an irregular, often fast manner that responds poorly to the needs of the body. Atrial fibrillation is the most common heart rhythm disturbance and it is defined as persistent if it lasts for more than 7 days. This can cause unpleasant symptoms such as palpitations, breathlessness, and increases the likelihood of suffering a stroke. Traditionally, it is treated by electric treatment (cardioversion), with long-term medication, or more recently by catheter ablation. Catheter ablation is a procedure which involves passing specialised wires through the blood vessels at the top of the leg to deliver small burn marks (ablation) to regions of the heart that cause AF. However, it has been demonstrated, for different heart rhythm problems, that ablating the outside of the heart as well improves the long term outcome. The aim of this study is to see whether additional electrical maps and ablation of both the inside and the outside of the heart results in improved outcomes in persistent AF. It will help provide valuable information for the management of this condition.

Who can participate?
People who are over 18 years old, have documented persistent AF and are suitable for catheter ablation

What does the study involve?
Many of the tests and procedures involved in the study will be the same as those undertaken for a standard internal ablation procedure and include:
History & clinical examination – this will have been done in the outpatient clinic.
ECG – to check for AF.
Blood tests – blood will be taken for routine tests (blood count, kidney/liver/thyroid function, and blood sugar levels).
Echocardiogram – This is a heart ultrasound scan that looks at the heart muscle and valve function.
Cardiac CT scan – Some, but not all patients will have a CT scan of the heart as part of their routine investigations.
In addition to the standard procedure, there will be an additional mapping and ablation (if required) to the outside of the heart. In order to do this, one additional tube is inserted under the breast bone so that we can access the outside surface of the heart. Taking part in the study will add about 30-60 minutes to the procedure time in order to conduct the research. This extra time is needed for the additional electrical maps and ablation.

What are the possible benefits and risks of participating?
There is a possibility that there will be no benefit for the patient taking part in the study, but it could decrease the likelihood of a recurrence of AF.

Where is the study run from?
Brighton and Sussex University Hospitals NHS Trust (UK)

When is the study starting and how long is it expected to run for?
July 2020 to July 2023

Who is funding the study?
Abbott Laboratories (USA)

Who is the main contact?
Dr Duncan Fatz

Trial website

Contact information



Primary contact

Dr Ian Mann


Contact details

Royal Sussex County Hospital
Eastern Road
United Kingdom
+44 (0)1273 696955

Additional identifiers

EudraCT number

Nil known number

Nil known

Protocol/serial number

CPMS 45979, IRAS 257470

Study information

Scientific title

Simultaneous Endo-Epicardial Mapping Of REcurrent Atrial Fibrillation (SEE MORE AF)



Study hypothesis

It is hypothesised that a combination of mapping and ablation to the inside and outside surface of the heart for patients with atrial fibrillation will improve the understanding of the causes of AF, and help improve the quality of ablation lesions, compared to procedures involving mapping and ablation to the inside surface alone. This might result in improved outcomes from ablation with regard to arrhythmia free survival.

Ethics approval

Approved 21/08/2020, East of England - Cambridge East Research Ethics Committee (The Old Chapel, Royal Standard Place, Nottingham, NG1 6FS, UK; +44 (0)207 104 8102, +44 (0)207 104 8101;, REC ref: 20/EE/0178

Study design

Observational cohort study

Primary study design


Secondary study design

Cohort study

Trial setting


Trial type


Patient information sheet

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


Atrial fibrillation


The procedure will be performed by a Consultant Cardiologist or Specialist Registrar with experience of catheter ablation for AF, and experience of techniques to gain access to the epicardial space. All patients recruited will have a clinical indication for AF ablation. This involves the placement of catheters within the cardiac chamber. All procedures will be conducted under general anaesthesia.

Standard clinical procedure:
Following general anaesthesia, an ultrasound probe is inserted down the oesophagus to ensure that there are no blood clots within the heart. Small tubes will be placed in the femoral veins to allow specialised catheters to be placed inside the chambers of the heart. Access into the left atrium, where the majority of AF ablation is undertaken, is carried out using a standard technique called a transseptal puncture. This involves a fine needle being used to create a small hole from the right atrium into the left atrium to allow passage of catheters. Following this, treatment can be delivered by making a series of small burn marks to restore the normal heart rhythm. During the procedure, it is common that patients require the heart rhythm to be restored to normal with a specially timed electrical shock, called a cardioversion.

Research protocol:
The research protocol represents only a small modification of the standard clinical procedure. Ordinarily, access to the outside of the heart is not undertaken and would represent an additional step. To allow access to the outside of the heart, a small tube is inserted underneath the breast bone and within the space between the pericardium (sac surrounding the heart) and heart. Specialised catheters can be introduced through this tube to allow electrical maps of the outside of the heart to be created. Areas of interest on the outside of the heart can be treated with ablation in addition to the areas inside the heart chamber with the aim of improving success rates. This will prolong the procedure by around 30-60 minutes. A standard procedure without the research protocol takes between 2 and 4 hours.

Intervention type



Drug names

Primary outcome measure

Recurrence of atrial fibrillation using electrocardiography and clinical assessment at 6 and 12 months

Secondary outcome measures

There are no secondary outcome measures

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Documented persistent AF
2. Suitable for clinically indicated catheter ablation
3. Aged > 18 years

Participant type


Age group




Target number of participants

Planned Sample Size: 20; UK Sample Size: 20

Participant exclusion criteria

1. Pregnancy
2. Current enrolment in another trial

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

Brighton and Sussex University Hospitals NHS Trust
Royal Sussex County Hospital Eastern Road
United Kingdom

Sponsor information


Brighton and Sussex University Hospitals NHS Trust

Sponsor details

c/o Scott Harfield
2nd Floor Sussex House
1 Abbey Road
United Kingdom
+44 (0)1273696955

Sponsor type

Hospital/treatment centre



Funder type


Funder name

Abbott Laboratories

Alternative name(s)

Abbott, Abbott U.S.

Funding Body Type

private sector organisation

Funding Body Subtype

For-profit companies (industry)


United States of America

Results and Publications

Publication and dissemination plan

The researchers plan to publish study results in peer-reviewed journals, and present data at conferences.

IPD sharing statement
The data-sharing plans for the current study are unknown and will be made available at a later date.

Intention to publish date


Participant level data

To be made available at a later date

Basic results (scientific)

Publication list

Publication citations

Additional files

Editorial Notes

25/08/2020: Trial’s existence confirmed by National Institute for Health Research (NIHR)