What is a Catheter Ablation?
A week or so before your ablation a CT (Click here for CT video) or MRI of your left atrium is performed so that we can import this into our EP Systems.
In this way we are able to show our Catheters position in your heart with great accuracy.
If the patient is on warfarin then this is stopped 5 days before the procedure. Subcutaneous heparin replaces this for 4 days before the procedure and missed on the day. This is because warfarin takes several days to wear off and heparin only a few hours. We want the blood thinned as close to the procedure but not at the start of the procedure when we make our punctures. Before the procedure the patient must have starved for at least at least 3-6 hours so that their stomach is empty and can be safely sedated. Immediately beforehand a transoesophageal echo is performed to ensure that there are no clots in the left atrium which can be dislodged by the catheters during the procedure. If there are then we delay the procedure for a few weeks and thin the blood with warfarin to allow the clots to dissolve.
The procedure is performed under local anaesthetic with sedation and involves an overnight stay in hospital. The local anaesthetic is introduced into the top of the legs and this allows us to pass the catheters into the veins. The catheters are passed up the veins to the heart. The catheters are passed into the left atrium by making a puncture in the atrial septum, the wall that divides the left and right atrium. This puncture heals up after a week or so. Once the catheters are in position the procedure can then start.
A number of techniques and approaches are currently used. The patient is often in atrial fibrillation at the beginning of the procedure (image of map of AF). We encircle the veins in pairs and join up these circles with lines between them (video of lesion set). We also confirm that electrical isolation has been achieved by using a pulmonary vein mapping catheter (image of lasso in vein). Once this has been completed the patient will hopefully have returned to sinus rhythm (map of sinus rhythm). If they haven’t then we perform an internal cardioversion. This is performed by passing a special catheter (x-ray of internal cardioversion catheter labelled LA with a mapping catheter (map) passed through a transseptal sheath (TS) and a multielectrode array (MEA) for mapping AF) to the heart which allows us to deliver a shock internally.
This requires less energy than external cardioversion and does not result in skin burns. The success of the procedure does not seem to be predicted by whether the patient returns to sinus rhythm with the cardioversion or with the ablation. Following the left atrial procedure we also perform an ablation of the isthmus between the tricuspid annulus and inferior vena cava which will also prevent atrial flutter occurring after the procedure.
After the procedure an echocardiogram is performed to make sure that fluid has not leaked out of the heart. The patient is then returned to the ward for close monitoring by the nursing staff. Once the heparin (blood thinning medication) has worn off the sheaths (fine tubes) in the groin can then be removed. After this another 2-3 hours of flat bed rest is required while the veins start to heal up and a little longer before the patient can get up and walk around. Even if the patient was not on warfarin before the procedure, warfarin will be re-started on the day of the procedure with the heparin being re-started the next day. The heparin will be continued until the warfarin has taken full effect which is usually about 4 days. The warfarin is to continue for 3 months...
It is not unusual to have symptoms of chest pain and palpitation after the procedure. Even if atrial rhythm problems occur these, can often resolve on their own after 3 months. We are not sure why this happens but it seems likely that inflammation of the atrium following the ablation can be one of the reasons.