Atrial fibrillation (or AF) is the commonest heart rhythm disturbance. It can develop as a consequence of high blood pressure, an overactive thyroid gland or heart valve and heart muscle abnormalities but in many cases there is no clear cause. It can also occur in very fit people such as marathon runners who do a lot of training. It is a rapid chaotic rhythm in the upper chambers (atria) of the heart and often results in a rapid irregular pulse which patients are often aware of, particularly when lying in bed. As the harmony between the 4 heart chambers is lost there is a reduction in the efficiency of the heart which can result in breathlessness or chest tightness. Some patients also report feeling sweaty or flushed.
When the attacks come and go it is called paroxysmal AF. If the atrial fibrillation does not stop or attacks last for more than seven days it is referred to as persistent AF.
Medical Treatment of Atrial Fibrillation
In all patients with atrial fibrillation it is important to look for an underlying cause such as high blood pressure or an overactive thyroid. If no cause is found the first line of treatment is medication to regulate the heart rhythm. These medications include beta-blockers like atenolol and bisoprolol, calcium channel blockers such as verapamil and diltiazem and other drugs like flecainide, sotalol and amiodarone. These drugs are often very effective in reducing the number and duration of attacks. If medications have been tried and are unsuccessful, or troublesome side effects develop another option that is considered in some patients is radiofrequency ablation.
Radiofrequency ablation of Atrial Fibrillation
This procedure aims to target the source of atrial fibrillation which in many patients are the veins which drain blood from the lungs into the heart (pulmonary veins). Rapid electrical activity in these veins often flood the atria with signals causing fibrillation. If it is possible to stop this activity from getting into the atrium, the fibrillation can be prevented.
The procedure is normally performed under local anaesthetic and sedation. Small tubes are inserted into a vein in the leg and catheters are passed through these up to the heart. The catheters are used to identify the pulmonary veins and one of the catheters can deliver high frequency electrical energy into the tissues to cause small spot burns around the mouth of the veins and in the left atrium. Most patients experience some discomfort from time to time during the procedure but this is usually relatively minor and is easily controlled by giving injections of sedation and painkillers during the procedure. The procedure takes between 2 and 3 hours. Patients can usually get out of bed approximately four hours after the procedure and sometimes can go home the same day. Sometimes patients will be kept in hospital overnight. Approximately 70% of patients will be completely free of AF and off medication after one procedure. A further 15% of patients will be free of AF but still on medication. Up to 25% patients choose to undergo a repeat procedure.
What are the risks?
Radiofrequency ablation for atrial fibrillation should only be performed in cardiac centres by experienced electrophysiolgoists as complications can occur. Some patients will suffer bruising or bleeding at the top of the leg where the tubes were inserted into the vein. This is generally minor and does not require any specific treatment other than some light pressure if bleeding is occurring. In approximately 1% of patients there can be bleeding around the outside of the heart. If this occurs, it can be necessary to insert a needle under the ribs to drain any collection of blood. This procedure is performed under local anaesthetic and the bleeding usually stops spontaneously. There is a small risk of clot formation at the site of treatment or on the catheters during the procedure. To minimise this risk, blood thinning medication is given regularly during the procedure but despite this there is still a 0.5% risk of stroke as a consequence of the procedure. Rarer complications include narrowing of the pulmonary veins (PV stenosis) which can present as progressive breathlessness. In addition, some patients can suffer from damage to a nerve which supplies the diaphragm, the large muscle between the chest and adomen used for breathing. This is usually a temporary phenomenon. Both this and pulmonary vein narrowing are rare.
What happens after the procedure?
After the procedure, your heart rhythm specialist may recommend that you take additional blood thinning medication. This could be an increase in the dose of heparin or to commence warfarin or to take clopidogrel. This is usually only for approximately a month.
In the first month, patients may also experience frequent episodes of palpitation due to the irritation caused by the ablation. This often settles down, but patients may need to restart or increase the dose of their heart rhythm medication for a few weeks.
The DVLA regulations state that patients are not allowed to drive for 2 days after the procedure.
Your heart rhythm specialist will probably want to see you in an outpatient clinic at some point after the ablation to ensure that the procedure has been a success and make any necessary changes to your medication. A heart rhythm monitor is usually done as well to confirm that the rhythm is stable.