Radio-frequency Catheter Ablation for Atrial Fibrillation (AF)

Introduction

Atrial Fibrillation (AF) can be treated by either trying to restore and maintain normal rhythm (rhythm control) or by leaving the heart in atrial fibrillation but controlling the rate (rate control).

What are the treatment goals in AF? The main treatment goals for patients with AF are: • Restore the hearts normal rhythm • Control the hearts rate • Reduce symptoms associated with AF • Reduce risks of stroke and blood clots What are the treatments available for AF? Treatment options include: • Medicines to control heart rate • Medicines to control heart rhythm • Anticoagulation (blood thinning medication) to reduce risk of stroke • DC cardioversion • Ablation • Left atrial appendage occlusion Treatment options depend on a number of factors: • How unwell (unstable) the patient is • If AF is new or chronic • If AF is intermittent (paroxysmal) or permanent • If the patient has other medical conditions

Rhythm control, if it can be achieved, is generally preferable unless the atrial fibrillation is particularly longstanding, causing no symptoms or has proved impossible to control by other means. 

Rhythm control is achieved by: - Anti-arrhythmic medication (such as Flecainide, Amiodarone, Sotalol) with or without: - DC cardioversion (an electrical shock under anaesthetic which abruptly terminates atrial fibrillation –

- Ablation

What is it?

Radio-frequency catheter ablation (RF ablation) is a process where the heart muscle is treated with heat energy from the inside of the heart so it can no longer transmit electrical signals.

RF Catheter Ablation targets the part of the heart muscle that is causing or spreading abnormal electrical signals. In most cases (90%) abnormal electrical signals causing AF start within the pulmonary veins which are connected to the left atrium of the heart.

RF Catheter Ablation damages the heart muscle inside the left atrium in order to block the abnormal signals from entering the heart. The ablation must therefore encircle the entrance of the veins in order to completely block the abnormal signals. In the majority of cases pulmonary vein isolation is sufficient to prevent AF reoccurring. Sometimes other areas of the heart muscle also need to be ablated. 

Why is it done?

This is currently considered appropriate in patients who have a significant burden of atrial fibrillation from which they have symptoms not controlled by antiarrhythmic tablets. Ablation can cure AF in many patients but is a challenging procedure that usually needs repeating, with moderately good success rates and small but significant and important risks.

What controls the hearts normal rate and rhythm? The normal electrical activity which stimulates the heart muscle to contract and therefore pump blood around the body, originates from an area called the Sinoatrial node located in the right atrium. The SA node releases electrical impulses in an organised way throughout the heart in order for its four chambers to contract in a synchronised way. Abnormalities occur if the electrical signal starts in the wrong part of the heart or follows the wrong path as it spreads across the heart.

What is Atrial Fibrillation? Atrial fibrillation is an abnormal heart rhythm characterised by rapid, chaotic and irregular contractions (fibrillation) of the upper chambers of the heart (atria). AF is an abnormality of the heart’s rhythm (its irregular) and rate (how fast it beats). Why is the heart rhythm abnormal in AF? Normal electrical impulses start in the Sinoatrial node. In AF electrical impulses are triggered from other places in the atrium and pulmonary vessels. This abnormal electrical activity causes the atria to contract in a fast, chaotic and disorganised way (fibrillation).

What are the symptoms of AF? • Palpitations • Shortness of breath • Dizziness • Chest pain • Feeling tired

How is AF diagnosed? • Clinical history • ECG – The hallmark of AF is absence of ‘p’ waves and an irregular rhythm on a tracing of your hearts electrical activity • Holter monitor

What are the risk factors for AF? The exact causes of AF are not known but it is more common in people with other heart conditions including: • High blood pressure • Coronary artery disease and heart attack • Heart valve disease • Cardiomyopathy • Congenital heart disease

AF is also linked to a number of other conditions and habits: • Diabetes • Pulmonary embolism • Lung cancer • Sepsis • Asthma • Binge drinking • Smoking

Will I need to do any preparation?

Deciding on ablation as the means of treating atrial fibrillation needs to be considered as embarking on a course of ablation procedures, requiring more than one procedure in most patients – most requiring 2 but some requiring more. After two procedures the success rates for retaining normal heart rhythm are around 80% (4 out of 5 patients) for paroxysmal atrial fibrillation and 60-70% (2 out of 3 patients) for persistent atrial fibrillation.

Pre-assessment Clinic You may be seen by a nurse or doctor in a pre assessment clinic a few weeks prior to the catheter ablation Your full medical history will be obtained and your suitability for the procedure will be determined following this. Any medications that need to be stopped or changed will also be addressed.

On the day Nil by mouth You will be asked to remain ‘Nil by mouth’ for six to eight hours before the procedure. This means you should not eat or drink during this time. This is to allow the doctor to visualise the structures clearly (without food being present in the gut) and also to reduce the risk of vomiting. Before the procedure 1. Arrival to the cardiac ‘cath lab’. 

If you are an inpatient you will usually be escorted by a nurse to the cath lab. This is a designated part of the hospital containing rooms that are used for cardiac catheter procedures. If you are an out-patient you will be asked to report to the unit at a specific time. You may have to wait in a waiting area until you are seen by a nurse who will go through a few identity checks and medical history with you. You will be given a hospital gown to change into. 2. Consent Form. 

Before the procedure you will be seen by the cardiologist performing the procedure who will also go through your medical history, blood results and any recent scans that you may have had. The cardiologist will explain the procedure in full, discussing the benefits and risks of catheter ablation. You will be asked to sign a consent form.

3. Cath lab. Cardiac catheter ablation is performed in a ‘lab’ containing specialised heart monitoring equipment, x ray equipment and a sterile area for the procedure. The cardiologist and assistants will be ‘scrubbed’ – like a surgeon would before an operation. This means they will decontaminate and wear special gowns to ensure the procedure is performed in sterile conditions.

4. Monitoring You will be attached to some monitors before the procedure, to measure your blood pressure, heart rate, heart rhythm and oxygen levels.

5. An oxygen mask will be placed onto your mouth and nose.

Technique

Anaesthesia

In most cases conscious sedation is used, however in some units and in some cases, a general anaesthetic is used. 1. Sedation Most procedures are performed under ‘sedation’. An intravenous cannula (small tube to allow administration of medications) will be inserted into one of the veins in your hand or arm. Most units use a sedative medication to cause relaxation in addition to medication to relieve pain. This is called ‘conscious sedation’ as you will not be asleep. 2. General Anaesthetic Some units and in ore complex cases you may require a general anaesthetic – where an anaesthetist will use medication to put you asleep.

What does it involve?

Transoesophageal Echocardiogram About 25% of patients having cardiac catheter ablation will need a transoesophageal echocardiogram to see if there is a clot in the heart.

1. The skin over the top part of your right leg will be shaved and cleaned with a disinfectant liquid.

2. A sterile sheet will be placed over your body from your neck to your feet. With the groin area exposed. 3. A small amount of local anaesthetic will be injected into the groin area 4. Once numb, the cardiologist will be make a small nick at the access point – usually the inner thigh. Small catheters (wires) will be inserted into the blood vessel and guided towards the heart.

5. Once the heart is reached the cardiologist will be able to see where the catheter is using a technique called fluoroscopy – this uses low energy x rays to create a live image on a screen. Various parts of the heart are tested to see if an abnormal heart rhythm can be stimulated.

6. The right side of the heart can be reached through the femoral vein that is accessed from the inner thigh. If the left side of the heart needs to be accessed – a small hole is created in the wall between the left and right atria.

7. Once the abnormal area causing AF is located – the cardiologist will use energy to ‘ablate’ or damage the area. The energy used is either radiofrequency (heat) or cryoablation (freeze).

8. To check to see if the treatment is successful the doctor will try to provoke an abnormal rhythm again. If this can not be done the treatment is considered successful. Further doses of energy can be given until success is achieved.

How long does it take? 

Usually between 2 and 4 hours.

Post procedure course (follow-up)

Following catheter ablation, you will be observed in a recovery area for 4 to 6 hours. You will be required to lie down for period of at least 2-3 to prevent bleeding from the catheter insertion site. After this you will be allowed to sit up for another 2-3 hours. 

Your heart rate and rhythm will be closely monitored by telemetry (continuous ECG tracing). Blood pressure, temperature and other vital signs will be recorded on a regular basis to ensure that all are within acceptable limits. Nurses will perform regular checks on your groin area to ensure there is no bleeding. You will usually feel tired due to the effects of sedation. 

The following day you may have an echocardiogram to ensure there is no fluid leak around the heart.

When can I eat and Drink? Usually you may eat and drink once you are fully awake.

Do I need someone to take me home? If you are going home you will require someone to escort you as the sedation takes time to wear off you will not be able to drive.

Will I be given any new medications? You may be asked to start taking daily aspirin or another blood thinning agent for several weeks, this is to prevent blood clots.

Should I take my usual medications after the procedure? You should continue to take your usual medications unless instructed by your doctor. If any medications have been stopped – the doctor will inform you when it is safe to restart these. Can I drink Alcohol? 

You should not drink alcohol for at least 24 hours after the procedure as the sedation can take time to wear off. Discuss this with your doctor.

How long will I stay in hospital?

Usually you will be allowed to go home the following day. Your doctor will see you and advise you about what medications to take.

What care will I need at home?

No particular care out of the ordinary.

Will I need someone to stay with me?

It is advisable to have somebody with you for at least 24 hours until the sedation has worn off

Will I need any special equipment when I go home?

No particular equipment is required.

What follow up care is needed/ What to look out for? 

1. Oozing from groin If your puncture site starts to ooze you can lie down and apply firm pressure on the area for around 10 minutes. If it continues to bleed or spurt blood you should seek urgent medical attention. Avoid taking a bath for 2-3 days as this could increase risk of bleeding. 2. Small lump in groin You may notice a small pea size lump in the groin area under the skin. If it becomes larger than this or starts to hurt you should seek medical advice It can take up to 2 weeks for patients to feel back to normal after the procedure. 3. AF returns Within the first few months after ablation – AF can come back. This could be due to inflammation in the heart muscle caused by the ablation procedure and not due to failure of the therapy. Sometimes medications to control AF may be restarted for a short while– your cardiologist will discuss this with you. Often the heart rhythm will spontaneously return to normal rhythm.

4. Chest pains Mild Chest pains can be occur after catheter ablation. It is often sharp and made worse y breathing or movement. It is caused by irritation to the area surrounding the heart. Pain killers can be taken to manage these symptoms. What symptoms should I seek urgent help for? • Increasing swelling and /or pain in the groin • Shortness of breath • Severe chest pain • Nausea • Fever • Weakness of one side of arms or legs, speech abnormality, loss of vision What should I avoid 1. Avoid heavy lifting for 7 days 2. Avoid rigorous exercise for 5 days. 3. Do not drive for at least 2 days 4. Do not fly for at least 7 days.

When can I start my normal activities again (e.g. driving, sports or work?)

Certain activities should be avoided that strain the catheter insertion site. Sedation can sometimes last longer than you think. During the first 24 hours after the procedure you should not drive, ride a bike, operate machinery or do anything that requires a skill. You should also not drink alcohol, take sleeping tablets or make important decisions.