CATHETER ABLATION OVERVIEW — Catheter ablation is a procedure that is performed to correct a disturbance in heart rhythm. It is usually called "radiofrequency catheter ablation," but it may involve either radiofrequency energy or cryothermal energy (see 'What is catheter ablation?' below). Catheter ablation is used to treat many abnormal, typically rapid and/or irregular heart rhythms.

A brief review of how a normal heart rhythm occurs and a description of some of the rhythm problems that are treated with this procedure will help in the understanding of catheter ablation.

How does the heart normally work? — Heart muscle cells are stimulated by electrical impulses that cause them to contract in a uniform way and with a regular rate. This contraction produces the heartbeat, which causes blood to be pumped out of the heart into arteries and then to all parts of the body. The flow of blood into arteries can be measured by feeling the pulse, which corresponds to the heartbeat.

In the normal heart, electrical impulses arise from an area of specialized cells called the sinus node, which is the heart's normal pacemaker. The sinus node is located in the right atrium, the upper right chamber of the heart (figure 1). After leaving the sinus node, an impulse spreads across the upper heart chambers (right and left atria) and reaches the atrioventricular (AV) node located near the center of the heart between the atria and the lower chambers, or ventricles, and then to conduction fibers that spread across the ventricles, which are the heart's main pumping chambers. As the impulse moves along the conduction fibers, cardiac muscle cells are stimulated and contract, producing a heartbeat (figure 2).

Sometimes, the electrical impulses "short circuit" the normal pathway and travel across the heart in an abnormal way. Abnormal pathways, or routes, for the impulses can develop, causing abnormalities in the heartbeat, or arrhythmias. In other cases, arrhythmias arise when areas other than the sinus node become active and begin to send out impulses that either compete with or take over the pacemaker function of the sinus node. Typically, the result of these abnormalities is a heartbeat that is too fast. This may develop in any location within the atria, AV node, or ventricles. When the fast rhythm requires tissue from the upper part of the heart, it is known as supraventricular tachycardia. When it requires tissue from the lower chambers only, it is known as ventricular tachycardia.

WHAT IS CATHETER ABLATION? — Catheter ablation is a procedure that can cure many types of fast heart rhythms. Using special coated wires that are moved to the heart, usually from the blood vessels in the groin, radiofrequency energy (low-voltage, high-frequency electricity) is targeted toward the area(s) causing the abnormal heart rhythm, permanently damaging small areas of tissue with heat. In some cases, cryoablation, which damages tissue by freezing rather than heating, may be used rather than radiofrequency energy. Other energy delivery systems are being developed.

The damaged tissue is no longer capable of generating or conducting electrical impulses. If the procedure is successful, this prevents the arrhythmia from being generated, curing the patient.

A pacemaker is a small electrical device that stays in the body and is connected to the heart with wires that stimulate the heart to contract in a regular way. In some patients, insertion of a pacemaker is a planned part of the procedure. In other cases, the need for a pacemaker is a complication of the ablation procedure. A doctor can tell whether a patient will likely need a pacemaker after the ablation. (See "Patient education: Pacemakers (Beyond the Basics)".)

WHICH RHYTHM PROBLEMS CAN BE TREATED? — Catheter ablation can be used to treat many arrhythmias that cause a fast heartbeat.

Catheter ablation may be recommended for:

●Paroxysmal supraventricular tachycardia, which includes:

•Wolff-Parkinson-White syndrome (see "Patient education: Wolff-Parkinson-White syndrome (Beyond the Basics)")

•AV nodal reentrant tachycardia

•Atrial tachycardia

●Atrial flutter

●Inappropriate sinus tachycardia

●Ventricular tachycardia and premature ventricular contractions

●Atrial fibrillation (see "Patient education: Atrial fibrillation (Beyond the Basics)")

THE CATHETER ABLATION PROCEDURE

Preparation — Patients may be asked to discontinue certain medications in the days before the procedure. In some cases, an imaging test of the heart, usually an echocardiogram, may be done in advance of the ablation procedure. Most patients are advised to stop eating and drinking at midnight the night before the procedure. A pregnancy test is usually done immediately before the procedure in women of child bearing capacity because of the radiation exposure.

Procedure — Before the procedure begins, you may be given a sedative medication through an intravenous (IV) line. Because this type of sedation is usually fairly deep, many patients are not aware of what is happening during the procedure.

Small coated wires (also called catheters) will be inserted into a blood vessel and then moved to the heart. The wires are usually inserted into the femoral vein or artery, in the inner thigh, and are then positioned within the chambers of the heart using fluoroscopy (low energy x-rays). Occasionally, catheters are inserted through veins into the side of the neck, upper chest, or arm. The doctor will test various parts of the heart and usually will try to provoke the arrhythmia.

The sections of the heart that are causing your arrhythmia can be usually be identified (figure 1). The right atrium and ventricle are reached through the femoral vein (in the thigh). If left atrial access is necessary, a small hole is made in the wall between the right atrium and left atrium. After identifying the cause of the arrhythmia, the doctor will then use the radiofrequency energy (heat or electrocautery) or cryoablation (freezing) to treat the problem area. During the procedure, your heart rate and rhythm, oxygen level, and blood pressure will be monitored.

When the procedure is completed, the doctor will again try to cause the arrhythmia to occur. If it cannot be initiated, the procedure is considered to be a success. However, if the arrhythmia can still be initiated, additional radiofrequency energy or freezing is delivered.

The length of the procedure varies from patient to patient, depending upon the type of arrhythmia being treated and other factors. Typically, the procedure lasts two hours or more.

Post-ablation care — You will be taken to a recovery area while the effects of the sedative medication wear off. The catheter site will be monitored for bleeding and the heart rhythm is observed closely during this period. You must stay in bed for several hours to reduce the risk of bleeding from the catheter site. You usually feel tired but well. Pain medication is usually needed for only a short time, if at all.

Some patients are admitted to the hospital after the procedure while others go home later the same day. Certain activities are not recommended for a brief period to avoid straining the catheter site.

You may be asked to take aspirin every day for several weeks after the procedure to prevent blood clots. After some ablations, a more powerful blood thinning medication is required (anticoagulant). The doctor will give more detailed information about medications needed after the procedure.

CATHETER ABLATION COMPLICATIONS — Like any invasive procedure, catheter ablation carries some risk. However, the risk of these complications is small in most cases.

Possible complications include:

●Problems related to moving the catheters through the blood vessels such as bleeding, infection, blood clots, bruising, and injury to the vessel(s).

●Injury to the heart as a result of the catheters; this includes a heart attack, perforation through the muscle, or damage to one of the valves within the heart.

●Blood clots that travel to the lungs (pulmonary embolism) or brain (stroke).

●Heart block or failure of any electrical impulse to travel from the top parts of the heart to the bottom. This complication, if permanent, requires implantation of a pacemaker.

●New arrhythmias.

●Exposure to radiation during the procedure. This can produce a very small increase in the risk of cancer or genetic defects. Efforts are made to limit radiation exposure during ablation procedures.

●Death (occurs in approximately 0.1 percent of cases).

OTHER ARRHYTHMIA TREATMENTS — Other arrhythmia treatments may be available, depending in part on what type of arrhythmia is present. Medication, pacemakers, cardioversion (delivering an electrical current to the chest to restore a normal rhythm), and surgery are examples of treatments that may be used for particular arrhythmias. (See "Patient education: Pacemakers (Beyond the Basics)" and "Patient education: Cardioversion (Beyond the Basics)".)

Some types of arrhythmias are temporary and non-life-threatening. Patients can be taught certain maneuvers (such as coughing or increasing pressure in the abdomen) that may stop the arrhythmia. Detailed information about available alternative therapies is available from a healthcare provider.

WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Catheter ablation for the heart (The Basics)
Patient education: Wolff-Parkinson-White syndrome (The Basics)
Patient education: Heart failure and atrial fibrillation (The Basics)
Patient education: Atrial flutter (The Basics)
Patient education: Ventricular fibrillation (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Pacemakers (Beyond the Basics)
Patient education: Wolff-Parkinson-White syndrome (Beyond the Basics)
Patient education: Atrial fibrillation (Beyond the Basics)
Patient education: Cardioversion (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Atrial fibrillation: Catheter ablation
Overview of catheter ablation of cardiac arrhythmias, section on 'Introduction'

The following organizations also provide reliable health information.

●National Library of Medicine

     (www.nlm.nih.gov/medlineplus/healthtopics.html)

●National Heart, Lung, and Blood Institute

     (www.nhlbi.nih.gov/)

●American Heart Association

     (www.americanheart.org)

●Heart Rhythm Society

     (www.hrsonline.org)

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