Ablation describes the process where we use a thin electrode catheter to 'burn' heart tissue in order to prevent short circuits occurring.  

Catheter ablation is a keyhole technique during which a small flexible tube (or catheter) is directed to a specific area inside the heart to deliver heat energy to damage (or ablate) abnormally active heart muscle. 

When the symptoms of AF are difficult to control with medication or when medication is not tolerated or desired, catheter ablation may be recommended as the next step in a patients care.

In some cases, patients can have a more regular but complex atrial tachycardia (AT), which requires a similar ablation approach. Usually, these are patients who have had heart surgery, have congenital heart defects or have undergone a previous ablation procedure.

In patients with AF, it is often the muscle sleeves around each pulmonary vein (veins draining blood from the lungs into the top chamber of the left side of the heart), which are targeted for ablation energy. 

A significant number of patients with AF will become free of AF or notice a marked improvement in their symptoms following catheter ablation. In more persistent cases of AF or in cases of complex AT, other areas within the upper chambers of the heart (atria) will be targeted.

What is the aim of the procedure? 

The aim of this procedure is to improve the symptoms caused by AF/AT, such as: 

  • breathlessness
  • palpitations
  • lack of energy
  • light-headedness
  • chest discomfort.  

In some cases, it is performed to improve heart function. It may also reduce the amount of medicine you have to take, some of which may have potentially harmful side effects.  

Although there is some evidence that the procedure might reduce the risk of stroke in the long term, as the procedure also carries a small risk this is not its primary aim. 

Before your ablation

This may vary between patients and you will receive separate advice prior to your admission in case we need to stop some of your medication before your procedure and upon discharge. This is to make sure you understand what each of the drugs you need to take are for.

If you are not currently taking warfarin, you will be asked to start warfarin before your ablation.

If you are currently taking a NOAC, we will ask you to swap this to warfarin unless this is contra-indicated or you are unable to tolerate it. 

Ideally, you should be taking warfarin for at least six weeks prior to your planned ablation. We recommended that you have weekly INR levels between two and three for at least four consecutive weeks leading up to the planned ablation. If your levels leading up to your ablation are above or below this range, you should immediately contact your arrhythmia nurse specialist. 

Warfarin should not be stopped for your procedure and will continue following your ablation. This will be reviewed at your outpatient appointment three months after your ablation. 

If you are unable to take warfarin and are taking one of the NOACs, you will need to stop taking it before the ablation. Normally, we recommend stopping this for between 24 and 36 hours, depending on which NOAC you have been prescribed, before your ablation. 

You should continue on all your medications up to your admission date, unless instructed otherwise. On the day of your procedure we will omit medication such as your anti-arrhythmics / beta blockers / calcium channel blockers. This is to avoid bradycardia following the procedure. We may also withhold any blood pressure medications on the evening before your procedure and on the day of procedure. This is to avoid hypotension (low blood pressure) during your procedure. 

If you are having your ablation at Harefield Hospital you may be asked to attend our pre-admission clinic. This is a nurse-led clinic run by the arrhythmia nurse specialist, who will assess that you are fit and ready for your procedure. This will include a routine blood test, physical examination (listening to your heart and lungs), ECG and MRSA swabs. You will also be seen by a member of the pharmacy team, who will check your medication. 

Please remember to bring details of your past medical history and a list of your current medications. 

You will be given a prescription for a drug called lansoprazole, if you are not already taking this (or a similar medication, such as omeprazole). You will be asked to start taking this one week before your ablation and should continue for six weeks after. Lansoprazole is a proton-pump inhibitor, which reduces the amount of gastric acid the stomach produces. We recommend this because the ablation takes place the left atrium, which is very close to the oesophagus (food pipe) and can cause some irritation, which this drug helps to reduce.

During your admission

Regardless of whether you are asked to attend the pre-admission clinic or not, you will be admitted the night before your procedure. You will be asked to contact the ward on the morning of your admission to check there is a bed available. 

You will be seen by a doctor/arrhythmia nurse specialist who will take a full medical history, blood test including your INR levels and examine you to ensure you are fit for the procedure. Lansoprazole will be commenced on admission if you are not already taking this (or a similar medication such as omeprazole) and will continue for six weeks following your ablation. 

The procedure will be explained to you in detail, including the associated risks, and you will be asked to sign a consent form.

Your anaesthetic

This is administered by an anaesthetist, who has had specialist anaesthesia training in the treatment of pain, the care of very ill patients (intensive care) and emergency care (resuscitation).

On the ward 

An anaesthetist will usually visit you on the ward before the procedure to discuss your anaesthetic. They will need to find out about:

  • your general health
  • prior experiences of anaesthesia
  • medicines you are taking
  • allergies you may have.

If you have caps or crowns on your teeth, please tell the anaesthetist as these can occasionally be damaged during anaesthesia.

Please take the time to talk to them about any previous experiences you have had with injections, hospitals stays or any concerns you have. The anaesthetist who comes to see you on the ward may not always be the same one who gives you the anaesthetic on the day of the procedure, but the information you give them will be passed on.

Occasionally, the anaesthetist may find something about your general health, for example a cold, rash or infection, that could increase the risks of your anaesthetic or procedure. If this is the case, it may be better to delay your procedure until the problem has been reviewed.

Eating and drinking

It is important that you have an empty stomach before the anaesthetic. Usually you must not eat anything at all for six hours before you go to the catheter lab, but you will be allowed to drink clear fluids until two hours before the anaesthetic. You will be told on the ward when you need to stop eating and drinking before the procedure. 

On the day of your procedure you will wait on the ward and be made ready for the ablation. There are usually two to three cases on any given day; the order is determined by the consultant, based on many factors.

You may be prescribed a sedative (pre-medication) to be taken before you go to the catheter (cath) lab. Pre-medication, or "pre-med", is given to you to help you to relax ahead of a procedure and will usually be in tablet form.

Once the staff in the cath lab have called for you, you will be taken to the cardiology department and will wait outside the doors to cath lab, which is the room where the procedure takes place. You will be accompanied by a nurse from your ward, who will stay with you until you are taken into the cath lab.

You will be greeted at the cath lab doors by one of the multidisciplinary team (MDT), and you will be asked to confirm your name and some details; this is to make sure you are the right person. 

The procedure

On the day of your procedure you will wait on the ward and be made ready for the ablation. There are usually two to three cases on any given day; the order is determined by the consultant, based on many factors.

You may be prescribed a sedative (pre-medication) to be taken before you go to the catheter (cath) lab. Pre-medication, or "pre-med", is given to you to help you to relax ahead of a procedure and will usually be in tablet form.

Once the staff in the cath lab have called for you, you will be taken to the cardiology department and will wait outside the doors to cath lab, which is the room where the procedure takes place. You will be accompanied by a nurse from your ward, who will stay with you until you are taken into the cath lab.

You will be greeted at the cath lab doors by one of the multidisciplinary team (MDT), and you will be asked to confirm your name and some details; this is to make sure you are the right person. 

In the cath lab

In the lab you will meet all the members of the MDT. It is important that you talk to the member of the cath lab team. They understand that you may be anxious about the procedure and are happy to answer any questions to help reassure you.

Please be prepared to answer several very important questions, such as name, date of birth and if you have any allergies, multiple times. Female patients will be asked if there is any chance they could be pregnant to avoid X-rays harming the fetus.

As with any ablation procedure that involves access to the heart's left atrium, it is routine practice to administer a blood-thinning medicine, known as heparin, at the beginning of the procedure to reduce the risk of blood clot formation during the ablation procedure.

The anaesthetic assistant will check your details, and you will be transferred onto the on the cath lab bed. The bed is surrounded by large TV screens, X-ray tubes and all the technology and equipment needed for the procedure. You will be at the centre of attention as multiple items for monitoring are attached to you. The cardiac physiologist will stick some cold sticky patches on your back before helping you to lie down and make yourself comfortable. 

The anaesthetist will then put a drip into a vein in your hand or arm, if you don't already have one, through which the anaesthetic can be given to send you to sleep. You may also be aware of them injecting some local anaesthetic into your wrist in order to place a small tube into an artery to allow close monitoring of your blood pressure. After this, you will receive some oxygen from a mask and the anaesthetist will start to give you the anaesthetic medication. Once you are asleep, a tube will be placed in your windpipe so that the anaesthetist can support your breathing during the procedure and further intravenous infusion lines (drips) will be inserted.

Under the anaesthetic

The next part of what is described happens while you are 'asleep' under a general anaesthetic. 

Once you are asleep, a transoesophageal echocardiogram (TOE) will be performed to exclude a blood clot (thrombus) in the heart. The TOE uses an ultrasound probe (a long thin tube) that is placed into your oesophagus (food pipe) and helps us perform the procedure safely. 

Using ultrasound we will make a detailed scan of your heart. If we see a thrombus (a blood clot), we will stop your procedure and reschedule it after you may had some more blood-thinning medication. The ultrasound probe will also monitor how well you heart is working during the procedure.

If you have any problems swallowing, please make sure that you tell your doctor this before the procedure as it may affect whether we use the probe or not. The TOE may also give you a sore throat and, in very rare cases, may damage the oesophagus.

What happens?

We make small cuts (incisions) at the top of both legs and place three to five small tubes (less than 3mm) into the veins near the groin area. These tubes allow us to pass thin, flexible, specially shaped catheters (electrodes) and other slightly longer sheaths up to the heart. 

We cross the electrical catheters from the right atrium into the left atrium through a small punctured hole (a transseptal puncture) made by a special needle. The catheters allow us to take pictures of the pulmonary veins and deliver the radiofrequency energy to the area around the veins. An advanced computer system, is used to create a 3D picture of the top of the heart. X-rays, ultrasound images and the electrical information, which comes from the electrodes being in contact with the chambers of the heart, are used to assess the electrical activity of each vein before and after ablation. 

Ablation describes the process where we use the thin electrical catheter to 'burn' the heart tissue to prevent short circuits occurring. This is like creating "fire breaks" around a forest fire to prevent it from spreading. We continue to ablate until we are sure we have created intact lines of ablated tissue. Just like in the forest, if the lines are not complete, the fire can spread. 

When the consultant is satisfied that the pre-planned ablation strategy has been achieved, we will ensure you are in a normal rhythm or reset your heart to sinus rhythm using cardioversion

Once in sinus rhythm, the catheters and sheaths are removed and manual pressure is applied to the entry site at the groin until any bleeding has stopped.

The length of your procedure will vary depending on factors such as how large your heart chambers are and whether you have paroxysmal or persistent AF. We usually find an ablation for paroxysmal AF takes two to four hours, whereas a procedure for persistent AF takes three to six hours.

After the procedure

When your procedure has been completed you will be taken to the recovery room, where you will be closely monitored until you are fully awake and ready to return to your ward. Once you are awake and your observations (blood pressure and heart rate) are stable, you will be taken back to the ward, where you will spend the night. You will be attached to a cardiac monitor to check your heart rhythm and blood pressure. 

You may have a pressure dressing applied to the top of your leg to reduce the risk of any bleeding from the vein which the catheters were placed in at the beginning of your procedure. For the same reason, you will remain in bed for three to six hours before being allowed to sit up and eventually stand up and walk again following your procedure.

The following day you will have an ultrasound of your heart (transthoracic echo) in the morning and be reviewed by one of the medical team. Providing you remain well and your echo shows nothing abnormal, you will be discharged home. You will normally be discharged after lunchtime. 

What to expect

What to expect immediately after your ablation

You may experience a:

  • sore throat
  • tenderness around the groin site
  • some chest discomfort
  • some AF or an atrial tachycardia (AT). An AT is a faster than normal heart beat, which feels regular in nature and can occur following an AF ablation.

What to expect once you are back at home

You should not drive for two days and avoid any heavy lifting or strenuous exercise for at least two weeks.

You can expect to feel tired after your ablation and may do for the first week or so. This is due to having a long procedure under a general anaesthetic. 

Your groin site may remain tender for a few days/weeks and you may develop some bruising around the puncture site. This bruising can spread up or down your leg and can take several weeks to go away. 

You have been through a procedure and your heart will need time to recover. Your heart will be inflamed and irritated. This is normal and means that you may experience episodes of AF/AT. It does not mean your ablation has been unsuccessful. 

The first three months of your recovery are called the "blanking period". You do not need to attend your local A&E unless you feel unwell, but do contact the arrhythmia helpline in normal working hours to let us know.

We recommend that you treat your AF the way you did prior to your ablation or as you were instructed when you were discharged.

What are the benefits?

The main benefit is to attempt to abolish your AF/AT and symptoms associated with it. If this is achieved, it may be possible to reduce/discontinue some of the medicines you are currently taking. 

This is often a very personal decision and your doctor will discuss this with you before and after your procedure.

Success rate

Your success rate will depend on the type of AF you have (paroxysmal or persistent), how long you have had AF and factors such as the size of your left atrium.

Paroxysmal AF

If you have paroxysmal AF your success rates are around 60 to 70 per cent with one procedure and increase to around 80-90% with multiple procedures (two, or, on rare occasions, three).

Persistent AF

If you have persistent AF your success rates are around 40 to 50 per cent with one procedure, increasing to around 80 per cent with multiple procedures (two or more)

Your success rates may be lower if you have been in AF for a long time and have a large left atrium.

In a small percentage of patients, it may be difficult to achieve long-term sinus rhythm and we may have to choose a rate control strategy.

Are there any risks?

No medical procedure is entirely without risk. It is important to remember that your doctor would not have recommended this procedure if they did not believe the potential risks were outweighed by the likely benefits to your wellbeing.

The overall risk of suffering any complication from this procedure is around three to five per cent. Some complications are minor, such as bruising, while others may be more serious, such as bleeding around the heart, which would require treatment.

As a comparison, the risk of life-threatening bleeding while on warfarin is around one to two per cent per year (ie out of 100 people taking warfarin, one or two will suffer major bleeding which requires urgent treatment). The success and risks of the procedure will depend on individual factors and it is important to discuss your individual case.


Complications can include:

  • Bleeding or bruising in the area of the groin where the catheter was inserted
    This is the most common complication from the procedure and is not normally serious (1 per cent, one in 100). You will be asked to keep your leg straight for a few hours after the procedure to minimise the risk of bleeding. When you leave hospital, you will be advised to avoid any strenuous physical activity or heavy lifting for at least one week. Sometimes the vessels in the legs can be damaged and require a procedure to repair them.
  • Atrial arrhythmia
    After AF ablation, the heart can sometimes develop an abnormally fast but regular rhythm from the atria, which is called atrial tachycardia. This may feel worse than AF but will often settle in the first few months after an ablation. If not, patients may need a cardioversion (electric shock treatment to restore a normal rhythm) or another ablation. 
  • Stroke
    This is an uncommon complication occurring in approximately 0.5 per cent (one in 200) of patients undergoing catheter ablation. This may occur during the procedure if a small blood clot or air bubble passes to the brain. As mentioned above, you will be given heparin during the procedure to reduce the risk of blood clots.
  • Phrenic nerve injury
    Catheter ablation next to the right upper pulmonary vein may occasionally result in damage to the nerve which runs near the heart. This nerve supplies part of the main breathing muscle, known as the diaphragm. If this occurs, it may lead to breathlessness, particularly when bending forward or while swimming. The incidence of significant phrenic nerve injury is less than 1%. Full recovery of phrenic nerve function has occurred without treatment in the vast majority of cases. Your doctor will follow up on this closely.
  • Bleeding around the heart
    Sometimes the catheters used for the ablation can make a small hole in the heart during the procedure and cause bleeding. This can usually be drained under local anaesthetic with a needle. This complication occurs in around 1 to 2 per cent (one or two out of every 100) patients having this procedure. Occasionally, surgery will be needed to remove blood which has collected around the heart and repair the hole.
  • Narrowing of the pulmonary veins 
    As explained above ablation is performed very close to the pulmonary veins. Very occasionally the veins react to this and become severely narrowed or even blocked. This does not usually cause any symptoms immediately. However, it is possible to cause breathlessness, recurrent chest infections or a blood-stained cough. Although symptoms from this complication are rare (0.5 per cent, one in 200), they can be very difficult to treat. This is usually attempted by placing a stent in the vein.
  • Damage to the native conduction system
    The risk of damage to your normal electrical system, resulting in the need for a pacemaker, is less than than 0.5 per cent (one out of every 200 patients). When the AF / AT is stopped, it is also possible that your natural pacemaker might not be functioning well. A pacemaker may be recommended but this is an underlying problem rather than a complication of ablation.
  • Infection or damage to the valves inside the heart
    Infection in the heart or of the heart valves (known as endocarditis) or damage to them is a very rare yet recognised complication following catheter ablation, with an estimated risk of approximately 1 in 10,000 patients (0.01 per cent). This can usually be treated with antibiotics, but sometimes surgery is needed. 
    In rare cases, a valve in the heart may be damaged from the ablation or one of the catheters becoming entangled in the valve. This usually requires no treatment but may require surgery.
  • Damage to food pipe
    Rarely, ablation from inside the heart can damage the food pipe, which is next to the heart. This can lead to infection, strokes or even death. Surgery is often needed to treat this problem. The ultrasound probe as its passed down can also damage the food pipe; it usually recovers on its own but rare cases can require surgery.
  • Collapsed lung
    If a tube is placed underneath the collarbone, sometimes the lung can be nicked by the needle leading to it deflating. This often gets better on its own but sometimes needs a drain to re-inflate the lung.
  • Chest infection
    An associated chest infection or fluid on the lungs may develop after the procedure and could need treatment with medication.
  • Other risk
    It's not possible to list all possible complications but they are very rare. Please discuss any concerns you have with your doctor.

Other ablation procedures

There may come a point where it is felt that the rhythm control strategy (tablets and/or AF ablation) was not successful and permanent AF may have to be accepted. Being permanently in AF is an arrhythmia status that a person can live with for many years.

Although in AF the heart beats irregularly, many of the symptoms are caused by the fast heartbeat, which results from the fast transmission of electrical impulses from the atria to the ventricles. The atrioventricular (AV) node is usually the only path via which the electrical impulses can pass from the atria to the ventricles.

Medications can help control the rate by slowing down the transmission of electricity at the AV node, but occasionally this is not adequate. One option is to perform an ablation at the AV node and permanently stop the transmission of electrical impulses from the atria to the ventricles. This means the atria will continue to be in fibrillation but that the ventricles will be beating so slowly a pacemaker will be required.

In this situation, patients who already have a permanent pacemaker are protected from a very slow heartbeat because the pacemaker takes control. However, most patients do not already have a pacemaker so the ablation cannot be performed safely until a pacemaker is implanted first, usually a few weeks before the date of the ablation or sometimes the same day. All patients who end up requiring AV-node ablation will be dependent on a pacemaker for the rest of their lives.

If you and your consultant decide that this is the appropriate procedure for you, it will usually take place under local anaesthetic. There will be a single sheath placed in the vein in your groin and an ablation catheter passed into your heart. The AV node will be found and this area will be ablated.

This procedure will make you reliant on your pacemaker, but will ensure a consistent and regular heart beat. The staff at your pacing clinic will ensure there is no impact on pacemaker function during or after the procedure.

Other cath lab procedures

You may visit the cath lab environment for some other procedures, including cardioversion. For example, if there is a problem with your anticoagulation medication and this makes you unwell, your consultant may place a small 'plug' in the left atrial appendage to prevent a blood clot forming in your heart.

These devices are placed in a similar procedure to an AF ablation. We use the same veins in the leg and cross from the right side to the left side of the heart in the atria.

Using transoesophageal echocardiogram (TOE), the plug is placed in the appendage and its stability is checked. When it is securely in place, the catheter is removed leaving just the plug in position.

Contacting the arrhythmia nurse specialist

When to contact your arrhythmia nurse specialist:

  • Hard swelling around your groin site that was not there prior to discharge.
  • New or increased breathlessness.
  • New or increased chest pain.
  • If you are having frequent AF episodes and need a medication review
  • If you experience AF which does not settle after a few days. A small percentage of patients may require a cardioversion within the first three months, but again this does NOT mean your ablation has been unsuccessful.

If you feel very unwell, you must see your GP or go to A&E. 

When do I stop my medications?

Your medication will be reviewed at your first follow-up appointment, three months after your procedure.

Your warfarinNOAC will not be stopped if your stroke risk is considered significant. This is because an AF ablation is not a cure and, if your AF recurs at some point in the future, you are more protected from a stroke. 

Your anti-arrhythmic drugs will be reduced and stopped at your first appointment if you have been well. Beta blockers and calcium channel blockers will also be reviewed at three months and will be reduced and/or stopped unless you have other indications to continue these long term. 

If you stop taking anti-arrhythmic medications after your first appointment, this will be reviewed at your next appointment. 

Follow up

You will have a follow-up appointment three months after your ablation either at Royal Brompton, Harefield or your local hospital. 

If your appointment is at Royal Brompton Hospital or Harefield Hospital you will see one of the members of the arrhythmia team.

Atrial tachycardia is an abnormal heart rhythm which is usually seen in patients that have undergone heart surgery, have congenital heart defects or have undergone previous ablation procedures.

Atrial fibrillation is an abnormal heart rhythm. It is the most common heart rhythm disorder in the UK.

Arrhythmia team

The arrhythmia team includes: 

  • EP consultants
  • clinical nurse specialists
  • an arrhythmia pharmacist 
  • catheter laboratory technicians.  


Clinical nurse specialists

  • Natalie Crump 
  • Sue King
  • Sarah Plowright 
  • Alex Wise 

Arrhythmia pharmacist


Harefield Hospital
01895 828979

Royal Brompton Hospital
020 7351 8364 

Useful links

If you want to know more about arrhythmia, here are some helpful organisations and websites: