Uses of catheter ablation
Catheter ablation is a procedure used to treat a variety of heart rhythm disturbances. Common uses of catheter ablation include treating supra-ventricular tachycardias (SVTs) including AVNRT, AVRT and atrial tachycardia; Wolff-Parkinson-White syndrome; atrial flutter; atrial fibrillation; ventricular tachycardia and ventricular ectopy.
In all these conditions, targeted areas of the heart’s electrical tissue is specifically damaged, i.e. ablated, to prevent the abnormal electrical circuits that are responsible for the condition. The tissue is ablated either by being heated (radio-frequency ablation, RF) or frozen (cryo-ablation).
Success rates from the procedure vary depending on the reason for doing it but are generally high Ablation may prevent the need for long-term medication to treat your condition and in many cases can be curative.
The catheter ablation procedure
Catheter ablation procedures are carried out in hospital, often as a day case or requiring a short stay. You may be asked to stop taking your anti-arrhythmic medications a few days before the procedure. This is because it is often necessary to provoke your abnormal rhythm during the procedure to be able to treat it most effectively.
The procedure will be carried out in the electrophysiology laboratory. This is similar to an operating theatre. You will lie on a thin bed similar to an operating table. The procedure will take between 1 and 4 hours depending on the condition being treated. There will be several people in the room throughout the procedure including at least one doctor, a nurse, a physiologist and radiographer. An anaesthetist will also be present if the procedure is carried out under general anaesthetic although this is not always needed. In the majority of cases a combination of local anaesthetic and sedating medications is used. The physiologist will prepare you for the procedure by placing lots of stickers (‘electrodes’) over your chest and back.
Long wires, called catheters, are placed in the heart via the bloodstream. These are most commonly inserted via a vein at the top of the right leg. Several catheters may be needed. An X-ray camera, which will move around close to your chest, is used to help position the catheters correctly inside the heart. Once in position the catheters can sense electrical activity in the heart and also deliver electrical energy to make the heart beat (‘pace the heart’) in a combination of ways. These ‘pacing manoeuvres’ can be used to identify the abnormal electrical pathways if required. This may involve triggering your abnormal heart rhythm and therefore cause some symptoms. It is usually straightforward to terminate these rhythms and therefore you should be in discomfort for any prolonged period. Medications to speed up or slow down your heart can also be used to help find the abnormal electrical pathways. If a general anaesthetic has not been used, you will be told when these are being given. Special software to create a virtual map of the inside of your heart may also be used during this stage of the procedure.
Once the team are satisfied that they have all the anatomical and electrical information needed they will begin the ablation itself. Depending on which area of the heart is being ablated, this can be uncomfortable and so, if a general anaesthetic has not been used, you may receive some pain-killing medication or sedative at this point. The size of the area to be ablated is highly variable depending on the condition being treated but can be as small as a few millimetres.
Once the ablation is complete, electrical testing is performed to ensure if the abnormal pathways have been destroyed. If they are still present further ablation may be required. Once the procedure is complete, the catheters are removed from the bloodstream. A small dressing is placed over the top of the leg and you will be transferred to the recovery area or ward.
After the radio frequency catheter ablation procedure
You will be observed for a few hours for symptoms, rhythm problems, and bleeding from the areas where the catheters were inserted. In many cases, at the end of this observation period you will be able to go home. You will be able to perform light activity (e.g. walking, stairs) almost immediately in most cases and resume full work or school activities within a few days. A follow-up visit to the doctor is often useful to check the ablation sites and review the procedure.
Possible complications of catheter ablation
Catheter ablation is a safe procedure and the chance of a significant complication from the procedure is very small. There may be some bleeding or bruising around the site of catheter entry (usually the top of the right leg). More serious complications are rare but include inflammation or bleeding into the protective sac around the heart (pericarditis or pericardial effusion) that may need to be drained off. If the ablation has been performed on the left side of the heart (most commonly for atrial fibrillation) there is a risk that clots may form on the tip of the catheter that can travel through the bloodstream and cause a stroke. For this reason, those having left-sided ablations will have blood thinning medication during the procedure (anti-coagulation). If the tissue being ablated is very near to the heart’s natural junction box (the AV node), there is approximately a 1% risk of damage to this junction box that would require a permanent pacemaker. You should discuss which of these risks are relevant to you with your cardiologist before your procedure.