Catheter ablation is a treatment for abnormalities of the heart rhythm (cardiac arrhythmias). It involves introducing a catheter (a thin tube) into the heart. The first part of the procedure involves mapping out the abnormal heart circuits in the upper (atria) and lower (ventricles) chambers of the heart. The second part involves interrupting, or disconnecting, the abnormal electrical circuits with the delivery of energy.
Different rhythm abnormalitites (arrhythmias) require different types of ablation:
• AV Nodal Reentrant Tachycardia (AVNRT): An extra pathway lies in or near the AV node, which causes the impulses to move in a circle and re-enter areas it already passed through.
• Accessory pathway: These pathways connect the atrium and ventricles and 'short-circuit' electrical conduction.
• Atrial fibrillation (AF): extra impulses originating from the pulmonary veins and the atrium make the atria beat very rapidly. Atrial fibrillation ablation is a complex procedure. In selected patients with intermittent ('paroxysmal') AF, the success rate is high (up to 90%). In patients with persistent AF, the success is lower. Repeat procedures may be necessary. The risks are generally higher than with ablations for other atrial arrhythmias.
The success rate of catheter ablation for paroxysmal AF is superior to anti-arrhythmic drugs. In experienced units, ablation for paroxysmal atrial fibrillation is successful in around 85% of patients, the procedure lasts less than three hours and the risk of complications is 1-2%. A repeat procedure may be required. The success rate is lower with longer durations of AF. The complication rate from AF ablation is 2-3%.
Catheter ablation for AF is best suited to patients with:
Paroxysmal AF who are troubled by symptoms and in whom treatment with at least one anti-arrhythmic medication has not been successful
Persistent or long-standing persistent AF may also benefit, but a lower success rate should be expected. Currently, there is currently no role for AF ablation in permanent AF.
• Atrial flutter: Extra impulses originating from different areas of the atrium cause the atria to beat, or 'flutter', rapidly.
• Ventricular tachycardia: If sustained, this is a life-threatening heart rhythm originating from the ventricles. It can lead to failure of the heart to pump and can present with breathlessness and loss of consciousness.
Catheter ablation involves introducing catheters (small plastic tubes) and wires into the heart. These are used to find the abnormal part of the heart that is causing the arrhythmia. Once found, a small amount of energy is delivered, so as to deaden it. Ablation procedures vary in their complexity, risks and benefits. Ablation of a Woolf-Pakinson-White pathway is low-risk and has a high success rate. Ablation for AF is more complex and the success rates vary according to the type of AF and individual patient characteristics.
Are there any risks?
Catheter ablation procedure is generally very safe. However, as with any invasive procedure, there are risks. Special precautions are taken to decrease these risks. Your doctor will discuss the risks of the procedure.
A thorough evaluation is needed to determine if catheter ablation is an appropriate treatment option for you. This evaluation may include:
• Medical history and examination
• Electrocardiogram (ECG)
• Echocardiogram (Echo)
• Holter monitor test
• An implantable loop recorder
• A cardiac MRI scan
What to expect from an ablation