Catheter Ablation for AF
Catheter ablation (using wires passed up from the leg to deliver energy to cause electrical conduction block) seeks to modify the electrical properties of the atria so that they are less likely to fibrillate in the future. There are a number of different techniques used at the moment which are evolving rapidly. Because of this the results of catheter ablation have improved rapidly and now most experienced centres will be able to offer patients with paroxysmal (intermittent) AF with no structural heart abnormalities an 80% chance of eliminating AF without drugs.
Some centres can also achieve this 80% success rate for patients with permanent AF. In order to achieve these results up to 50% of patients need to have repeat procedures. Results published by some centres can be confusing because some do not even follow patients up in person let alone do Holter monitoring (a continuous recording of the ECG lasting from 24 hours to 7 days exclude asymptomatic AF (AF without symptoms). Other centres do not make it clear how many patients require repeat procedures or the help of antiarrhythmic drugs to keep them in normal sinus rhythm.
- Benefits – catheter ablation can restore normal sinus rhythm and avoid the need for drugs. There is early evidence that mortality may be reduced by catheter ablation but this is yet to be confirmed. There is also early evidence that catheter ablation of patients with AF and heart failure can have their heart function improved by restoration of sinus rhythm by catheter ablation.
- Success rates – 70% to 80% off drugs after multiple procedures. This is likely to be lower if patients has structural heart disease (e.g. valve disease)
- Complications occur in about 1 to 5% of patients. The most common complication is pericardial effusion (blood leaking out of the heart) which may need draining with a needle or operation. This is the result of the anticoagulation (blood thinning) drugs required to be given during the procedure. The main reason for this is to avoid clots forming on the catheters. If clots do form then they may be dislodged and travel to the arteries feeding the brain. This could cause stroke. Other complications include bruising in the legs, and chest pain. Chest pain can be relieved by pain killers during the procedure but can persist for a few weeks because of the inflammation from the procedure.
Simple pain killers can be used to alleviate this until it settles. Another complication is narrowing of the pulmonary veins. These are the veins that drain blood from the lungs into the heart and is related to how far into the veins energy is applied and how much energy is applied. This does not appear to have been a problem since we adopted a policy of only delivering very low energies near the veins. The rarest but most concerning complication is atrio-oesophageal fistula. This has happened 14 times in world experience so far. It is a complication which occurs 2 weeks or so after the ablation when a hole forms between the atrium and the oesophagus (gullet).
The first symptoms are stroke like symptoms followed by vomiting blood and death. Only 2 patients have survived this complication. No one knows what causes this complication but it may be related to delivering a lot of energy particularly in the back of the atrium. Many centres deliver 100 watts into the left atrium to achieve their results. We only deliver 30 watts in the atrium and 20watts near the veins. For more information see 'What is Catheter Ablation'.
4. Surgical ablation – performing AF surgery is done using a number of energy sources. It is most often performed at the time of other surgery, or example mitral valve surgery but it is also performed as a stand alone procedure. It can also be performed via small punctures in the chest using thoracascopes thus avoiding the need to make large incisions in the chest.
The procedures have to be performed under general anaesthetic and require one of the lungs to be deflated. Complications occur in a similar order as catheter ablation and the success rates are about the same although again the follow up in many centres is poor so the outcomes are often not clear.