Definition of atrial fibrillation Kadlec Regional Medical Center Cardiac Electrophysiology Atrial Fibrillation Ablation Atrial fibrillation is a heart rhythm disturbance that causes an irregular (and often rapid) heartbeat. It replaces the normal heartbeat, which originates in the sinus node (Figure 1). Figure 1 During atrial fibrillation, the top chambers of the heart (the atria) lose their normal, organized electrical activity and develop a chaotic, unorganized rhythm that makes the bottom chambers (the ventricles) beat irregularly (Figure 2). Atrial fibrillation often causes an erratic fluttering sensation in the chest, or palpitations. Atrial fibrillation makes the heart a less efficient pump, and this may result in symptoms of weakness, fatigue, dizziness, or shortness of breath. However, some patients who have atrial fibrillation are completely unaware of it, and have no symptoms at all. Page 1 of 5
Figure 2 Atrial fibrillation may be paroxysmal or chronic. Paroxysmal atrial fibrillation refers to atrial fibrillation that comes and goes on its own. The episodes may last anywhere from a few minutes to several hours, and sometimes several days. Chronic atrial fibrillation is the type of atrial fibrillation that persists once it comes on. In patients with chronic atrial fibrillation, treatment is necessary to restore a normal heart rhythm. Because of the sluggish movement of blood through the atria during atrial fibrillation, there is a tendency for blood clots to form in some patients with atrial fibrillation. This can lead to complications such as stroke, even in patients who have otherwise been unaware that they had atrial fibrillation. For this reason, medications that thin the blood, such as aspirin or warfarin (Coumadin), are necessary for some patients with atrial fibrillation. Whether or not a blood thinner is needed depends on the particular circumstances of each individual patient. Some individuals feel fine when they are in atrial fibrillation. This is more often the case in older patients who are not very active than in younger patients with active life-styles. If the atrial fibrillation is not causing any symptoms, sometimes the best course of action is to simply live with it, instead of receiving medications or other types of treatment in an attempt to restore a normal heart rhythm. If the decision is made to live with the atrial fibrillation, medications may still be needed to prevent a rapid heart rate, and to prevent blood clots. There are several options available for the treatment of atrial fibrillation. No direct treatment - Patient has no significant symptoms or adverse effects from the atrial fibrillation. Treatment with rate-controlling medication and blood thinners may be all that is needed. Page 2 of 5
Antiarrhythmic medications These medications are designed to prevent atrial fibrillation from occurring. Because of potential side effects, most of these medications must be started while monitored in the hospital. Cardioversion Electrical cardioversion is a procedure in which an electric shock is delivered to the chest wall, in order to restore a normal heart rhythm in a patient with atrial fibrillation (Figure 3). It is an effective and useful way to restore a normal rhythm, but only if the atrial fibrillation has not been present for a long time. If the atrial fibrillation has been present for more than a few months, there is a high probability that it will return shortly after cardioversion. AV Node Ablation - Ablation can also be used to purposefully disrupt the electrical connection between the top and bottom chambers of the heart. In atrial fibrillation the top chambers deliver impulses to the main conducting wire at a fast rate which in turn causes the bottom chambers to beat quickly and irregularly. By ablating or destroying the main conducting wire, the ventricles can no longer race in response to the atrial fibrillation. Therefore, an AV Node ablation is always coupled with implantation of a permanent pacemaker in order to provide a steady heart rate after the ablation. Catheter Ablation This is an ablation procedure designed to prevent atrial fibrillation from occurring. It is performed through small puncture sites in the blood vessels. See below for more details. Surgical Ablation/MAZE This is a type of left atrial ablation or pulmonary vein isolation procedure that is performed either during open heart surgery for other indications or as a surgical procedure targeting the atrial fibrillation alone. There are various forms of the procedure involving minimally invasive techniques to open heart surgery. It is believed that atrial fibrillation may occur as a result of extra electrical impulses arising from the pulmonary veins as they enter the left atrium. There are, on average, four pulmonary veins that drain the oxygenated blood from the lungs to the heart. The blood enters the left atrium from the lungs and travels to the left ventricle and finally out into the aorta and the rest of the body. The junction of the pulmonary veins with the more muscular left atrium has been shown to be electrically active in patients with atrial fibrillation. Catheter ablation techniques have therefore focused on electrically isolating these veins from the left atrium preventing the impulses from causing a disorganized rhythm in the atria. Radiofrequency catheter ablation of atrial fibrillation involves the delivery of radiofrequency (RF) energy to the walls of the left atrium to essentially burn or cauterize the tissue around the pulmonary veins to prevent it from conducting electricity. Lines of burns are created in a circular pattern around the pulmonary veins. Special tubes and wires, called catheters, are placed from the groins up the veins and into the heart. From the right atrium a small needle is used to puncture a hole in the wall between the right and left atria in order to get to the left atrium. This is called a transseptal puncture. Once in the left atrium, the ablation procedure is performed. Why you need an atrial fibrillation ablation The most common indication for an atrial fibrillation ablation is continued symptoms related to the atrial fibrillation despite attempts at control with medications and cardioversion. Occasionally an atrial fibrillation ablation is performed in a patient with no symptoms who has suffered from adverse effects related to the atrial fibrillation such as a weakened heart muscle despite medication and cardioversion. The success rate of an atrial fibrillation ablation is approximately 70-75%. Success is determined by no further symptoms related to the atrial fibrillation. About 25% of patients will need at least a second ablation procedure to achieve this success rate. Page 3 of 5
The risks of an atrial fibrillation ablation Potential complications from an atrial fibrillation ablation include: Bleeding and infection at the procedure site (< 1%) Skin burns (< 1%) Poking a hole in the blood vessels or heart (called a perforation) with possible bleeding into the sac around the heart (called effusion with possible tamponade) or into the chest cavity. These complications may require open heart surgery to repair. ( 1%) Poking a hole in the lining of the lung (called a pneumothorax). This may require a small tube to be placed into the chest to expand the lung while the lining heals over 2-3 days. (< 1%) Heart attack, stroke, and death (< 1%) Creation of an abnormal communication between the left atrium and esophagus (tube connecting the throat and stomach) called an atrio-esophageal fistula. This can be life-threatening and often requires surgery to repair. (< 1%) Damage to the normal conduction system requiring a pacemaker (< 1%) To prepare: Blood tests may be ordered by your doctor in preparation for the procedure. Prior to scheduling the ablation procedure, your doctor may order a special MRI or CT scan to look at the pulmonary veins and the left atrium. This helps to plan the procedure from an anatomical perspective. In some patients there may be abnormal pulmonary vein configurations. Your doctor may also prescribe a medication called Lovenox which is a blood thinner that is injected under the skin similar to the way insulin is administered. This medicine is designed to the keep the blood thin while the warfarin (Coumadin) is stopped. This is often prescribed for the five days prior to the ablation procedure. Ask your doctor what medications you are allowed to take. Your doctor may ask you to stop certain medications one to five days before your procedure (such as aspirin, blood thinners, or rhythm medications). If you are diabetic, ask your doctor how you should adjust your diabetic medications. Bring a list of all medications with you. Do not eat or drink anything after midnight the evening before your procedure. If you must take medications, drink only with a sip of water. When you come to the hospital, wear comfortable clothes. You will change into a hospital gown for the procedure. Leave all jewelry or valuables at home. You will need to stay in the hospital at least overnight. Bring items with you (such as a robe, slippers, and toothbrush) that may make your stay more comfortable. When you are able to return home, arrange for a companion to bring you home. What to expect: You will be given a hospital gown to wear. You will lie on a bed and the nurse will start an intravenous (IV) line in your arm so that medications and fluids can be administered during the procedure. You will meet with a member of the Anesthesia Department who will provide general anesthesia during the procedure. The right and left groin areas will be shaved and cleansed with an antiseptic solution. Sterile drapes are used to cover you from your neck to your feet to prevent infection. It is important that you keep your arms and hands down at your sides and not disturb the drapes. To remind you, some type of restraint may be used to prevent your hands from coming in contact with the sterile field. Page 4 of 5
The nurse will connect you to several monitors. Prior to the induction of general anesthesia a special heart ultrasound will be performed called a transesophageal echocardiogram. While sedated a small ultrasound probe is passed through the mouth into the esophagus in order to take high-definition pictures of the heart. The goal of this test is to make sure there are no blood clots in the heart prior to the ablation procedure. After the induction of general anesthesia, the catheters will be placed through several puncture sites in the right and left groins. A small monitoring catheter is placed in one of the arteries in the groin with the remainder of the catheters placed in the veins. The number of catheters is determined by the needs of the procedure but can be up to three catheters in both the right and left veins of the upper leg. The catheters and wires are then advanced through the veins and into the heart. The transseptal puncture is then performed in order to access the left atrium. A small ultrasound catheter is also placed into the heart through the vein in order to monitor the puncture procedure. This is called an intracardiac echocardiogram. Intravenous blood thinners are given to prevent blood clots from forming during the ablation. The ablation procedure is then performed as outlined above. An electroanatomical (3D) mapping system is used to help guide the ablation procedure. Cardioversion may be performed following the ablation to restore normal rhythm. An atrial fibrillation ablation can take 4-6 hours. After the procedure: The catheters will be removed once the blood is no longer thinned. After the catheters are removed it is important to keep the access sites immobilized for 4-6 hours. You may be admitted to the hospital at least overnight. You will be placed on a special monitor called telemetry that allows your heart rhythm to be displayed on monitors in the nursing unit. Before you leave the hospital, your doctor and nurse will talk to you about activity, medications or any follow-up appointments. An antiarrhythmic medication will be continued or started following the ablation procedure and continued for at least three months. Warfarin (Coumadin) will also be continued. Do not drive for 48 hours after an ablation. Do not lift anything greater than 10 pounds for 1 week. Keep the puncture sites clean and dry for 48 hours. Use an occlusive dressing while bathing or showering during this time. Patient signature Date Physician signature Date Page 5 of 5