A healthy heart beats in a predictable and smooth rhythm. This rhythm is stimulated by electrical impulses generated within the heart muscle. When the heartbeat becomes abnormal, the rhythms it produces are called arrhythmias. When the heart is beating more than 100 times per minute, this type of arrhythmia is called tachycardia, a potentially dangerous condition. It is caused when the electrical impulses in the heart’s electrical network travel along irregular pathways or repeat the same pathways over and over.
Ablation is a procedure to restore normal rhythm by destroying very small, carefully selected parts of the heart that cause tachycardia. In most cases, ablation refers to the use of catheters to destroy the selected areas of heart tissue. However, ablation can also be performed during open-heart surgery.
The minimally invasive method of ablation involves inserting a thin tube (catheter) through a blood vessel (in the upper thigh, wrist or arm) and all the way up to the heart. This tube is tipped with equipment to destroy the selected cardiac tissue, usually with radiofrequency energy. This procedure is often performed by a heart specialist called an electrophysiologist. Ablation has become the preferred technique for treating many forms of tachycardia, and the American Heart Association estimates that radiofrequency ablation (the most common type) is used successfully over 90 percent of the time.
Depending on the cause of the underlying arrhythmia, there still may be a need for antiarrhythmic medications or an implantable cardioverter defibrillator (ICD). Patients with atrial fibrillation or ventricular tachycardia, for example, may require continued use of antiarrhythmic medications. The type and severity of an arrhythmia may also require more invasive surgery in order to correct the problem.
The heart’s electrical system is rather complex. Electrical rhythms begin as impulses emitted from the sinus node, also known as the heart’s “natural pacemaker,” which cause the atria, or upper chambers of the heart, to contract. From the sinus node, these impulses travel across a specific route, or pathway, through the AV node and into the lower chambers of the heart ventricles. Once they reach the ventricles, the impulses cause the chambers to contract in a routine and consistent manner. If the impulses are interrupted, delayed or sent down the wrong path, the heartbeat may become irregular, too fast or too slow. If the heartbeat becomes too fast, ablation is often the best management option.
About ablation and catheter ablation
Ablation is a procedure to destroy very small, carefully selected parts of the heart that are causing tachycardia – an abnormally fast heartbeat. Ablation enables the heart to beat more slowly and normally again. Catheter ablation has become the preferred technique for treating tachycardia. It has replaced direct-current shock ablation, and is more frequently taking the place of some open-heart surgeries and long-term use of antiarrhythmic medications. Although there are several forms of catheter ablation, the two most common are radiofrequency ablation and cryoablation.
Radiofrequency ablation uses radio energy to heat and destroy the defective tissues. It is by far the most common form of ablation.
Cryoablation uses intense cold to freeze and destroy the tissues. As with radiofrequency ablation, cryoablation involves insertion of a catheter through a blood vessel and up to the heart. However, rather than delivering radiofrequency energy, a highly specialized catheter produces extreme cold in the area. This causes tiny ice crystals in and around the abnormal cells, destroying those cells.
Ablation may be used to treat any of the following conditions:
AV nodal reentrant tachycardia. A condition in which the heart's electrical system “short circuits” due to an extra pathway in, or adjacent to, the AV node.
Wolff-Parkinson-White syndrome. A condition in which the normal electrical signals in the heart travel along an extra, abnormal electrical pathway. This can cause an abnormal heart rhythm (arrhythmia). The condition is believed to be present from birth (a congenital heart defect). In certain cases, physicians might recommend ablation for young adults who have Wolff-Parkinson-White, but do not experience symptoms. Ablation has been shown to lower the risk of developing serious heart-rhythm abnormalities later in life.
AV junctional tachycardia. Abnormally fast heart rhythms that result from electrical impulses originating in the AV junction, the area of the heart that includes the AV node, the area just above the AV node, and the area just below the AV node.
Atrial fibrillation. The extremely rapid and uncoordinated contraction of the upper chambers of the heart (atria).
Atrial flutter. A condition similar to atrial fibrillation except that the rapid firing of impulses occurs in a regular pattern, rather than uncoordinated.
Atrial tachycardia. Abnormally fast heart rhythms that result from electrical impulses originating in one of the two upper chambers of the heart (atrium).
Ventricular tachycardia. Abnormally fast heart rhythms that result from electrical impulses originating in one of the two lower chambers of the heart (ventricle).
Ventricular fibrillation. Recent data suggests that VF, in certain patients, may be initiated by a trigger that can be identified and ablated. However, this procedure is used as a preventive measure. Once ventricular fibrillation has begun, it is an extremely dangerous condition that requires immediate intervention to prevent sudden cardiac death.
A third type of ablation, alcohol septal ablation, is used in some cases to treat hypertrophic cardiomyopathy, or abnormal enlargement of the heart muscle that constricts blood flow. During this procedure, the physician uses injections of alcohol (ethanol) to cause a “planned heart attack” in the septum, or wall of muscle that separates the right and left sides of the heart.
Patients with atrial fibrillation or ventricular tachycardia may need to continue antiarrhythmic therapy after ablation. Patients undergoing ablation of the AV node typically require a pacemaker. Also, some patients, especially those who are at higher risk of ventricular arrhythmias, may be required to have an implantable cardioverter defibrillator (ICD). These devices monitor the heart rhythm and interrupt dangerous and severe ventricular arrhythmias with a strong electrical shock. They can be combined with pacemakers.
Before catheter ablation
Before the catheter ablation is scheduled, electrophysiology studies will be performed to locate exactly where the abnormal rhythms are coming from. During an electrophysiology study (EP study), a catheter is placed into a blood vessel and fed all the way up to the heart.
Once in place, the catheter is able to detect and map electrical currents in the heart. In this way, physicians are able to precisely pinpoint where abnormal impulses are originating. Once the physician has located the source of the arrhythmia(s), the catheter ablation can be scheduled. Additional tests that may be performed before ablation include an electrocardiogram, echocardiogram and maybe others, depending on any underlying conditions.
Patients may be instructed not to eat or drink anything for up to 8 hours before the ablation procedure. Any prescription drugs that manipulate the heart's electrical system may also be discontinued, including beta blockers, calcium channel blockers, digoxin and certain antiarrythmic drugs. On the day of the procedure, they will be admitted to the hospital. A nurse or physician will explain what is going to happen, and patients are encouraged to ask any questions that they may have.
During catheter ablation
In the hospital’s electrophysiology laboratory, an intravenous (I.V.) line is run into the patient’s arm. The I.V. delivers a sedative and other medications. Small devices will be attached to the patient's body to allow the physician to monitor the heart rate, typically with an echocardiogram.
Typically, the groin/upper thigh area is the site from which the catheter will enter the body on its way to the heart. The arm or wrist are other options. The site is cleansed, shaved and numbed with a local anesthetic. An anticoagulant is administered to reduce the risk of blood clots forming during the procedure. The catheter is then fed through the blood vessel (e.g., the femoral artery in the groin/upper thigh) and up into the heart. There may be some minor discomfort during this period.
As the catheter is guided to the heart, the physician will likely be watching the progress on a fluoroscope, or an x-ray machine that provides continuous, real-time images inside the body.
When the catheter reaches the target area, energy from the tip of the catheter will be used to destroy the heart cells that are creating the tachycardia. While this is happening, the patient may experience light-headedness, rapid heartbeat or chest pain. When the procedure is complete, the catheter is withdrawn. In all, the procedure may take about six hours.
After catheter ablation
Once the procedure is completed, the patient will be moved to a recovery room. He or she may feel groggy from the sedative. The catheter insertion site may be bruised and sore.
If the groin area was used as the point of catheter insertion, then the patient will be instructed to lie in bed with legs out straight. The physician may choose to use one of two techniques for removing the sheath that was placed at the initiation of the procedure. The traditional technique is to wait until the effects of the anticoagulant have passed (four to six hours) and then to apply pressure while removing the sheath. A newly developed technique allows the sheath to be removed immediately after the procedure through the use of hemostatic devices that seal or stitch the femoral artery.
If the wrist or arm was used as the point of catheter insertion, then the patient does not need to stay in bed. Throughout the post-procedure monitoring, the point of catheter entrance will be checked for bleeding, swelling or inflammation. Vital signs will be continuously monitored. Usually the patient stays overnight for further observation and is discharged the next day.
Patients are given instructions from the medical staff regarding the following:
Exercise and exertion. Patients are reminded to refrain from lifting heavy objects and engaging in strenuous exercise or sexual activity for 24 hours after the procedure.
Care of the incision area. Bruising and soreness are possible and normal. Undue pain, swelling or inflammation may require medical attention.
The function and use of medications.
Potential risks with catheter ablation
Although a catheter ablation is a standard approach that is widely used, there are some risks during or after a catheter ablation. These risks include the following:
Damage to the heart from either the movement of the catheter or its heat, which may require a pacemaker to correct it
Bruising
Leakage of the blood vessels
Damage and scarring to the pulmonary veins, which return blood from the lungs to the heart. Radiofrequency ablation has been shown to cause narrowing of the pulmonary veins, which may result in symptoms such as shortness breath of, coughing, chest pain, or coughing up blood. This condition is sometimes misdiagnosed as pneumonia, lung cancer, or blood clots in the lung. It can be treated by opening the narrowed pulmonary veins.
Rare complications that occur in less than one percent of patients include heart attack, stroke or sudden death, often resulting from blood clots that break loose during the procedure.
About surgical ablation
While catheter-based techniques are relatively safe and effective for many types of arrhythmias, there are occasions when surgery is necessary. One of the following surgical ablations may be recommended:
Maze-like procedure. This is open-heart surgery to correct severe symptoms of atrial fibrillation that do not respond to various forms of treatment, including medications, cardioversion and catheter ablation. Small cuts are made in the heart to create a new pathway through which electrical signals can travel. The Maze procedure itself is not considered a type of surgical ablation. However, surgeons are using a Maze-like approach. Instead of tiny incisions in the atria (the upper chambers of the heart), ablations are made to either the epicardium (thin membrane surrounding the heart) or endocardium (thin membrane lining the inside of the heart).
Endocardial resection. Also used to treat ventricular tachycardias, endocardial resection involves the partial removal of one layer of the heart endocardium.
Research into ablation as a treatment for heart rhythm disorders is ongoing. Recent findings include the following:
Radiofrequency ablation carries its highest success rate when performed early in the disease process, before transient AF progresses to the more chronic form.
Temperature-controlled catheter ablation has had the highest success rate in treating AV junction tachycardia.
New mapping techniques promise to make the procedure more precise, expanding it to additional arrhythmias.
Questions for your doctor
Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about ablation:
Does my heart condition require ablation?
Is there any risk associated with ablation? Could it harm my heart?
How successful do you expect this procedure to be?
Which form of ablation would you recommend for me?
Is there anything I need to do to prepare for this procedure?
After the ablation is performed, will I require any further surgery? How often will I need to followup with a physician?
How long will it take me to recover from this procedure? Will I need to stay in the hospital?
Am I taking any medications that might interfere with this procedure?
