AF Ablation | Mysite

CATHETER ABLATION FOR ATRIAL FIBRILLATION

A guide for patients by Malcolm Barlow

In a medical context, ablation means the destruction of abnormal or unwanted body tissue. In the heart this is achieved using special catheters inserted into the heart, hence the term “catheter ablation”. This technique was first used to treat rhythm disturbances (arrhythmias) in humans in the late 1980’s. It was first used to treat atrial fibrillation (AF) in the mid 1990’s. However, widespread interest in AF ablation didn’t develop until after 1998. I first began performing ablation for AF in Newcastle in 2001. Nowadays catheter ablation is considered a standard procedure in the management of AF.

IS AF ABLATION FOR YOU?

Studies have shown that AF ablation is the most effective tool against AF we have, more effective than any medication. Many patients testify to its life-changing benefits. It is a relatively safe and minimally-invasive procedure (the heart is accessed via the vein in the groin). It is quick, taking on average <90 mins, and recovery is fast, with patients able to leave hospital within 24 hours, and able to return to full physical activity within a few days.
However, it is not the treatment of choice for all patients. Though safe, it is not entirely risk-free. And, although medication is not as effective, it may still prove sufficiently effective for many months or even years. And, as medication is generally safer, it should be tried before ablation is considered. Consequently, ablation is generally reserved for those who continue to experience relatively frequent episodes of AF despite appropriate medication, or who are unable to tolerate medication.
It is important to understand that we do not yet have a “cure” for AF, and that AF ablation is simply the best of our current treatment options. A small number of patients (<5%) will experience prolonged freedom (>10 years) from AF, and may never develop AF again. The great majority (90%) experience a dramatic reduction in AF burden, and many will remain free of AF for years but, ultimately, if we wait long enough, AF will return in almost all patients. This should not be seen as a failure of the procedure but as the inevitable consequence of progression of the underlying causes for AF in the first place. The chance of a successful procedure is strongly influenced by a number of factors (see box below), and those patients with a number of negative predictors should only consider ablation if symptoms are severe, or if there is underlying cardiac dysfunction.

AF is associated with an increased risk of stroke, and many patients will be taking oral anticoagulant medication, depending on the presence or not of other risk factors, to reduce this risk. Unfortunately, there is no conclusive evidence yet that AF ablation reduces the risk of stroke. In general therefore, whatever the outcome of the AF ablation procedure, if anticoagulants were necessary beforehand, they will be continued after the ablation.
The main problem with AF for most people is the symptoms its causes. These include feelings of fatigue, breathlessness, weakness and/or palpitations. The severity of symptoms varies

Factors Influencing AF Ablation Outcome

Type of AF - intermittent, self-limiting AF (paroxysmal AF) has a higher chance of success than persistent AF.
Duration of AF - irrespective of whether the AF is paroxysmal or persistent, AF which has been present for many years has a poorer chance of successful outcome.
Left atrial size - the larger the left atrium, the less the chance of a successful procedure.
Sleep apnoea - untreated sleep apnoea predicts a poor response to ablation.
Left ventricular dysfunction - the presence of reduced cardiac function and heart failure predicts a poorer response to ablation, however such patients have the most to gain from a successful procedure.
Age - has not been shown to be a predictor of success or the lack of success.

considerably however, and some experience no symptoms at all. And, as we are not yet certain that successful AF ablation reduces the risk of stroke, the main reason for AF ablation remains the treatment of symptoms.

A number of recent studies have demonstrated an improvement in heart function, and increase in survival, in patients with underlying cardiac dysfunction undergoing successful AF ablation. So, this too is an indication for the procedure.

THE AF ABLATION PROCEDURE

The procedure takes place in the cardiac catheter laboratory. This “cath lab” employs high-quality X-ray equipment, necessary to allow visualisation of the thin catheters and wires used in cardiac procedures. It also contains very sophisticated monitoring and mapping equipment, necessary for the diagnosis and ablation of arrhythmias.
Normally, you will be given intravenous sedation (“twilight anaesthesia”) to make you comfortable during the procedure, rather than being put completely to sleep (general anaesthesia). Usually sedation is all that is necessary as the procedure is not distressing. In the private hospital my anaesthetist will administer the sedation and will vary the depth of this as required. If necessary this can be converted to general anaesthesia.
Catheters are inserted into the right femoral vein in the groin and threaded up the large main vein into the heart (see diagram). One

1. Ablation catheters in LA_preview03.jp

or more sheaths are then passed from the right atrium to the left atrium via a thin membrane between these two chambers (the fossa ovalis). To allow this, usually an opening has to be created in the membrane, though sometimes one is already present. Various catheters are then positioned in the left atrium depending on the type of AF ablation procedure.

What follows is a presentation of the two main techniques for AF ablation - pulmonary vein isolation (specifically the cryoballoon technique, which I use as my primary technique) and left atrial posterior wall isolation (which I use if a repeat ablation is necessary). Other, less common, techniques are briefly addressed in the box below.

PULMONARY VEIN ISOLATION

Pulmonary vein isolation (PVI) is the cornerstone of AF ablation and is always performed first. Of all the possible ablation techniques, this has the greatest benefit.

The pulmonary veins, which carry blood from the lungs, connect to the back of the left atrium (see diagram). Where they join the heart, “sleeves” of heart muscle extend 1-2 cm into these veins. Heart muscle is quite different to vein muscle, and is capable of independent electrical activity. In a landmark paper, Häissaguerre and colleagues demonstrated that electrical activity coming from these veins was responsible for triggering AF in nearly all of the 45 patients he studied.
Since then, numerous studies have demonstrated that electrical isolation of these pulmonary veins normally results in a significant reduction in AF. Understandably, this was thought to be due to elimination of the triggering activity from these veins. However, it is now believed that this procedure has other effects which contribute to its benefit (e.g. alteration of autonomic nerves behind the left atrium).
Electrical isolation is achieved by ablation at the pulmonary vein-left atrium junction (see diagram next page). This can be achieved by heating or freezing the heart muscle to create small areas of scar. The scar cannot be electrically activated and so acts as an electrical barrier between the heart muscle in the vein and the heart muscle in the atrium. Think of it like a road cutting through a forest.
Heating ablation is usually delivered point-by-point using a radiofrequency ablation catheter. This was the traditional method used for PVI, and is still used by many operators. I use this method for other arrhythmias and for other AF ablation techniques, but for PVI I prefer the cryoballoon method.

THE CRYOBALLOON METHOD

Since 2008, I have been using a cryoballoon to achieve pulmonary vein isolation (as of 2016 I have performed more than 350 cases). I believe this technique is faster and safer than point-by-point radiofrequency ablation.
A 28 or 23mm balloon is placed at the pulmonary vein mouth to occlude the vein. The balloon is then frozen, using liquid N2O, and ablation is achieved through freezing (the temperatures achieved in the balloon are typically between -40ºC and -70ºC). This creates a complete circular scar at the vein-atrium junction in one action.
One or two freezes are delivered to each vein in turn. At the end, all the catheters and sheaths are removed and a temporary stitch placed at the insertion site in the groin to prevent bleeding from the vein. Usually, the procedure takes about 75 mins.
Using this technique, following a single procedure, there is a 60-80% chance of remaining free of symptomatic AF for ≥ 2 years, and a 40-60% chance of remaining so for ≥ 5 years. The chance of success depends on the factors mentioned previously. Although AF may return, for greater than 90% of people the burden of AF

(the frequency and duration of episodes) is dramatically lessened compared with pre-procedure.

During the procedure you may experience chest discomfort, particularly when freezing is delivered to the left lower pulmonary vein. An “ice-cream” headache can also be experienced. Some people experience an urge to cough during or after the freeze. Make every effort not to cough during the freezing, as this can lead to rupture of pulmonary capillaries. Finally, we will stimulate the nerve running to the right diaphragm (right phrenic nerve) when freezing at the mouth of the right-sided veins, as damage to this nerve is a risk of the cryoablation procedure. You may experience this as a “kicking“ sensation in the right upper abdomen, when the diaphragm contracts in response to stimulation of the nerve. My anaesthetist will vary the level of sedation to ensure that none of these sensations are severe.

LEFT ATRIAL POSTERIOR WALL ABLATION

Some patients experience an inadequate initial response to pulmonary vein isolation, and a further procedure may be necessary. More commonly, a second procedure may be required due to recurrence of AF months to years after initial successful PVI. My current practice is to ablate the back (posterior) wall of the left atrium, between the pulmonary veins. Radiofrequency energy is used for this purpose.
The aim is to eliminate electrical activity on the back wall, which can be achieved by delivering numerous point-by-point ablation applications to the entire back wall, or by creating continuous lines of ablation to form a “box” around the back wall.
The pulmonary veins are also checked at this time to confirm that they remain electrically isolated from the first procedure. If not, radiofrequency ablation is delivered to re-isolate these veins.
Some operators create a larger “box”, and include the pulmonary veins within the box, as their initial procedure. This achieves isolation of both the pulmonary veins and the back wall of the left atrium at the same time. I prefer the cryoballoon method for PVI, so I do not usually use this “large box” technique.

OTHER AF ABLATION TECHNIQUES

Left Atrial Lines

This refers to the creation of continuous lines of ablation within the left atrium, away from the pulmonary veins, using radiofrequency energy. However, a recent study found no benefit in treating AF when this approach was added to pure pulmonary vein isolation.
There is experimental and surgical evidence to suggest that AF can be prevented by creating large electrically-disconnected areas within the left and right atria. In fact, the earliest attempts at AF ablation attempted just this. However, it remains technically extremely challenging, using just a catheter-based approach, to successfully create the multiple lines necessary for this outcome.
Consequently, only certain limited lines (such as the posterior wall “box”, “roof” or “mitral isthmus” lines) are routinely used these days.
Left atrial lines are sometimes added to pulmonary vein isolation, but most commonly they are used in the treatment of left atrial tachycardias, which can develop out of the blue, or sometimes after AF ablation.

Left Atrial Rotor Ablation

There is experimental evidence that multiple rotors (think of electrical “tornadoes”) are present during sustained AF. Some researchers have reported success in mapping and ablating these rotors.
At present this is controversial (many do not believe the reports) and only available in a small number of international centres.

CAFE Ablation

“Complex atrial fragmented electrogram” ablation refers to the targetting of complex electical signals within the left atrium which can be seen during AF.
This was a popular technique in the past but it is doubtful that it is beneficial by itself.

POSSIBLE COMPLICATIONS

As with all procedures, catheter ablation for AF does have risks. The risks are small, but some can be serious and permanent. The following complications are listed to inform, not to alarm. Not every possible complication is listed.

Minor Complications

Minor complications resolve without specific treatment, and cause no permanent damage. Most of the “complications” listed here are not preventable but are unavoidable consequences of the procedure.

Chest pain after the procedure is relatively common. It is caused by irritation of the lining of the heart from the ablation process (pericarditis). This usually disappears within 48 hours, and responds to anti-inflammatory medications, such as ibuprofen.
Oesophageal injury is common following the procedure. Usually there are no symptoms, but occassionally it may produce reflux-like symptoms or chest pain. It usually settles within 1-2 weeks, and responds to antacids.
Cough may develop as a result of irritation to the lung tissue adjacent to the pulmonary veins. This may persist for weeks to months. Rarely, minor amounts of blood can be coughed up in the first couple of days post-procedure.
An increase in heart rate by 10-20 bpm is an uncommon consequence of the ablation, due to damage to nerves behind the left atrium. This is not harmful, is associated with a higher success rate, and will slowly normalise.
Bruising at the groin access site is not uncommon but rarely a problem. Sometimes a soft lump can develop or bruising can travel down the leg. This will disappear over a few weeks.

Phrenic Nerve Palsy

Damage to the nerves travelling to the diaphragm (phrenic nerves) is a risk of ablation. If the nerve is damaged, the diaphragm will fail to work properly on that side, until it recovers. This can lead to increased breathlessness, temporary collapse of the

lower part of the lung, and infection in the collapsed part of the lung. The risk is rare with radiofrequency ablation but, if it occurs, damage is permanent. On the other hand, there is a 1-3% risk of damage to the right phrenic nerve with cryoballoon ablation, but in almost all patients there is full recovery, although in some cases this may take many months.

Major Complications

The risk of a serious or permanent complication is rare, and overall, the chance of any major complication with this procedure is <1%.

Groin access site complications - rarely this can require corrective vascular surgery.
Perforation of the heart or a major vessel during the procedure - this can usually be handled by the placement of a draining catheter into the sac surrounding the heart. Very rarely open heart surgery may be required.
Stroke - from an air bubble or from a clot forming during the procedure.
Pulmonary vein stenosis - rarely a narrowing of one or more of the pulmonary veins may develop weeks to months after ablation. It may lead to breathlessness. This is much less likely with cryoballoon than radiofrequency ablation.
Gastroparesis - damage to the nerves surrounding the oesophagus can lead to paralysis of the stomach. Recovery takes many months.
Heart attack - a possible complication of all ablation procedures.
Atrio-oesophageal fistula - a very rare but potentially fatal complication which can develop in the first month post-procedure. It is much less likely with cryoballoon ablation (0.001%) than with radiofrequency ablation (0.1%).

PROCEDURE PREPARATION AND RECOVERY

SVC Isolation

Occasionally AF triggers arise from the main vein entering the right atrium from the head and neck, the superior vena cava. Electrical isolation can be beneficial in these cases. Care must be taken to avoid permanent damage to the right phrenic nerve (which supplies the right diaphragm).

Surgical AF Ablation

Increasingly, AF ablation is performed at the time of cardiac surgery, most commonly at the time of mitral valve surgery.
Both radiofrequency and cryo-ablation are utilised, using specially designed instruments.
Pulmonary vein isolation is standard, along with closure of the left atrial appendage. Sometimes, left and right atrial lines are also created.
However, as is the case with non-surgical AF ablation, there is no evidence yet that the addition of atrial lines to pulmonary vein isolation is beneficial.
Uncertainty regarding both the benefits of surgical ablation and the choice of ablation lesion sets has led to wide variation in practice among surgeons.

Preparation

Take all your usual medications on the morning of the procedure, unless specifically advised differently. You may take these with half a glass of water. If you are diabetic, the hospital will inform you about medication/insulin dosing and timing.
I like all my patients to take their usual anticoagulant (apixaban, rivaroxaban, dabigatran or warfarin) on the day of the procedure at the usual time. If you normally take this in the morning do so on the day of the procedure. However, if your procedure is being performed in the public hospital you may be assigned to another doctor who may prefer you to withhold the anticoagulant. If this is the case the hospital will inform you regarding if and when to cease your anticoagulant.
Your groin will be shaved completely on both sides. This is to allow sterile access to the vein in the groin during the procedure. Certain parts of your chest hair will be shaved to allow placement of ECG electrodes.
If you have an allergy to the contrast agent, or an iodine allergy, please inform my secretaries at least a week before the procedure. If you have other allergies, make sure to inform the hospital staff on the day of the procedure.

Recovery

If you are discharged from hospital the day of the procedure (the usual arrangement in the public hospital), you will need a responsible adult to stay with you the night after the procedure.
Rest on the day after the procedure. You should avoid strenuous activity until 1 week post-procedure. You may not drive for the first 48 hours.
If you experience sharp central chest pain in the first 48 hours, made worse by breathing, coughing, or moving, this is probably pericarditis. Take Ibuprofen. If it does not settle, contact my rooms.
Some people experience an increase in AF activity in the first month after the procedure. Do not be concerned as this is well-described. Contact my rooms if it does not settle.
It is important to continue your anticoagulant for at least 1 month after the procedure. You will need to discuss with your cardiologist whether it is safe for it to be stopped at this time or not. Other medication changes will be discussed with you prior to leaving hospital. You will normally be given an antacid medication, to be taken for 4 weeks to reduce oesophageal irritation.
You should arrange to follow-up with myself a few months post-procedure, and your regular cardiologist as directed.

Is AF Ablation For You?

The AF Ablation Procedure

Pulmonary Vein Isolation

The Cryoballoon Method

LA Posterior Wall Ablation

Other AF Ablation Techniques

Possible Complications

Preparation and Recovery