Ablation of atrial fibrillation
Encyclopedia
The ablation of atrial fibrillation is an invasive technique that is used in the treatment of Atrial fibrillation
(AF in the UK or Afib in the US), one of the most common cardiac arrhythmias. Ablation
is the removal or melting away of an unwanted structure or tissue. Ablation of atrial fibrillation can be accomplished with different techniques; the most established approach is via radiofrequency ablation
around the pulmonary vein
s, which are the veins that bring oxygenated blood from the lungs back to the left side of the heart.
introduced an open-heart surgical procedure which has been subsequently established as capable of curing Atrial Fibrillation. This procedure was originally called the Maze procedure
. In its latest design, it is called Maze III. It consists in a series of incisions and sutures that create many compartments in the atria. A minimally invasive version, or Minimaze
has also been developed. Specialists in cardiac electrophysiology
attempted to replicate the Maze procedure results using internal catheters, and therefore no incisions, as early as the late 1980s. Only in the 1990s the pioneering work of Michel Haïssaguerre
's group focused on the role of the pulmonary veins as the trigger of Atrial Fibrillation .
, heart failure and increased risk of death.. These complications are more frequent in less healthy individuals, such as patients over age 75, with diabetes, heart failure or heart valve malfunction. In many cases, the condition can be controlled with medication, either by reducing the heart rate ("rate control") or by maintaining a regular rhythm ("rhythm control"). In a significant proportion of people, drugs are either ineffective or lead to unacceptable side effects. In those cases, electrophysiology-based treatment modalities such as ablation treatment may be employed. Younger patients with normal cardiac anatomy and function have the highest probability of maintaining normal rhythm while taking antiarrhythmic drugs.
Currently, many high specialization centers around the world, especially in Europe and the US, but also South America, are dedicated to the safe and effective use of this procedure. The procedure is thus performed in many EP labs. It is currenly recommended that it be carried out with the help of a 3D mapping system. The most common form is an ablation of the pulmonary veins and surrounding tissue.
or via a thoracoscopy
approach. The most common approach is the first, or catheter based. In this case the catheter that delivers the ablative energy can use radiofrequency
, ultrasound, laser or cryothermic energy
. The ablative catheter is able to deliver lesions only from its tip, which is from 4 to 8 mm long, shaped like a match point.
The ablation points are centered in the left upper chamber of the heart, or left atrium
. A series of ablation points is used to establish a line of lesions. This lines are supposed to block the trigger points of Atrial Fibrillation and create a barrier to the propagation of the arrhythmia. As stated, the lesions target the entrance of the pulmonary veins, of which usually two right and two left ones are found. The lesion points are applied inside the left atrium a few millimeters from the pulmonary vein insertion in the body of the left atrium. This region is known as pulmonary vein antrum . The end point of the procedure is to electrically isolate the pulmonary veins - pulmonary vein isolation or PVI. A less common approach is to encircle both pulmonary vein orifices on one side with a single wider elliptical line, technique called WACA or wide area circumferential ablation. Other lines of lesions and ablation points inside the left and right atrium are often made - mostly on the posterior wall and often also on other targets, such as the coronary sinus
, the left atrial appendage base, the superior vena cava
, the right atrial isthmus. Currently, area of complex fragmented signals, called CFAE are also treated with ablation points in order to reduce the risk of recurrent AF. The procedure takes between 2 and 4 hours and occasionally needs to be repeated. As a general rule, older patients with more heart disease and more frequent, longer episodes require more extensive ablation procedures . A technique using a ballon capable of creating lesions all around its perimeter is also being used with less effective results.
, perforation of the free wall with ensuing a strangling collection of blood around the heart, that is known as cardiac tamponade
, a clot flowing from the heart into the brain causing an embolic stroke and narrowing of a pulmonary vein near its insertion in the heart which in the worst case scenario can lead to death of a piece of lung tissue. In experienced centers, the major complication rates should not exceed 2-4%. Currently the procedure is accomplished under anticoagulation with oral and intravenous medications
Long term effects and advantages of the procedure are not fully known. In one 5 year study from Germany, most patients remained in normal rhythm after 5 years. Efficacy in patients past their 60's is being studied by an ongoing, long term study, in part sponsored by the US national heart, blood and lung institute. It is advised by leading scientific institutions that anticoagulants could be safely stopped in patients who are taking them because AF increases their risk os stroke a few months after a successful procedure .
Various studies have compared the effects and risks of ablation of Afib versus use of antiaarhythmic drugs All of them have shown that ablation therapy is more effective than antiarrhythmic drugs, in particular in younger patients with a healthy heart and if the ablation is done by highly skilled practitioners.
In general, to be considered candidates an ablation for AF, patients should be 1 ) symptomatic for the arrhythmia (one of the following symptoms : palpitations, shortness of breath, fatigue and or weakness, dizziness ) 2 ) have tried and failed at last one antiarrhythmic drug, 3) should be free of severe lung disease, 4) should have normal size or mildly dilated atria (upper heart chambers) , 5) normal or mildly reduced cardiac function, Following ablation, most of these patients are free of recurrent AF at least at 1 year or later.
Atrial fibrillation
Atrial fibrillation is the most common cardiac arrhythmia . It is a common cause of irregular heart beat, identified clinically by taking a pulse. Chaotic electrical activity in the two upper chambers of the heart result in the muscle fibrillating , instead of achieving coordinated contraction...
(AF in the UK or Afib in the US), one of the most common cardiac arrhythmias. Ablation
Ablation
Ablation is removal of material from the surface of an object by vaporization, chipping, or other erosive processes. This occurs in spaceflight during ascent and atmospheric reentry, glaciology, medicine, and passive fire protection.-Spaceflight:...
is the removal or melting away of an unwanted structure or tissue. Ablation of atrial fibrillation can be accomplished with different techniques; the most established approach is via radiofrequency ablation
Radiofrequency ablation
Radio frequency ablation is a medical procedure where part of the electrical conduction system of the heart, tumor or other dysfunctional tissue is ablated using the heat generated from the high frequency alternating current to treat a medical disorder...
around the pulmonary vein
Pulmonary vein
The pulmonary veins are large blood vessels that carry blood from the lungs to the left atrium of the heart. In humans there are four pulmonary veins, two from each lung...
s, which are the veins that bring oxygenated blood from the lungs back to the left side of the heart.
History
In 1987, Dr. James CoxJames Cox
James Cox may refer to:* James Cox , United States Representative from New Jersey, 1809–1810* James Cox , , starting quarterback for the Colorado Buffaloes football team, 2005–2006* J. B...
introduced an open-heart surgical procedure which has been subsequently established as capable of curing Atrial Fibrillation. This procedure was originally called the Maze procedure
Cox maze procedure
The Cox maze procedure is a type of heart surgery for atrial fibrillation."Maze" refers to the series of incisions arranged in a maze-like pattern in the atria...
. In its latest design, it is called Maze III. It consists in a series of incisions and sutures that create many compartments in the atria. A minimally invasive version, or Minimaze
Minimaze
The mini-maze procedures are cardiac surgery procedures intended to cure atrial fibrillation , a common disturbance of heart rhythm. They are procedures derived from the original maze procedure developed by James Cox, MD....
has also been developed. Specialists in cardiac electrophysiology
Cardiac electrophysiology
Cardiac electrophysiology is the science of elucidating, diagnosing, and treating the electrical activities of the heart. The term is usually used to describe studies of such phenomena by invasive catheter recording of spontaneous activity as well as of cardiac responses to programmed electrical...
attempted to replicate the Maze procedure results using internal catheters, and therefore no incisions, as early as the late 1980s. Only in the 1990s the pioneering work of Michel Haïssaguerre
Michel Haïssaguerre
Michel Haïssaguerre is a prominent French cardiac electrophysiologist. He was born in Bayonne, France, on October 5, 1955. He became a Professor of Cardiology in 1994. His present position is Professor at the Hôpital Cardiologique du Haut–Lévèque, Bordeaux–Pessac...
's group focused on the role of the pulmonary veins as the trigger of Atrial Fibrillation .
Indication
At least 2.2 million people in the US alone suffer from atrial fibrillation. It represents by far the most relevant heart rhythm related clinical issue, due to its complications including strokeStroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
, heart failure and increased risk of death.. These complications are more frequent in less healthy individuals, such as patients over age 75, with diabetes, heart failure or heart valve malfunction. In many cases, the condition can be controlled with medication, either by reducing the heart rate ("rate control") or by maintaining a regular rhythm ("rhythm control"). In a significant proportion of people, drugs are either ineffective or lead to unacceptable side effects. In those cases, electrophysiology-based treatment modalities such as ablation treatment may be employed. Younger patients with normal cardiac anatomy and function have the highest probability of maintaining normal rhythm while taking antiarrhythmic drugs.
Currently, many high specialization centers around the world, especially in Europe and the US, but also South America, are dedicated to the safe and effective use of this procedure. The procedure is thus performed in many EP labs. It is currenly recommended that it be carried out with the help of a 3D mapping system. The most common form is an ablation of the pulmonary veins and surrounding tissue.
Methods
Atrial fibrillation ablation can be performed from the inside of the heart via catheters that are introduced from the groins or neck; in this case, no incisions are made. Alternatively, it can be accomplished from the outside of the heart with either open heart surgeryOpen Heart Surgery
Open Heart Surgery was released on August 8, 2000 by rock band Virginwool. The band signed to Breaking/Atlantic Records after initially beginning signed to Universal Records. The album was produced and mixed by Brad Wood....
or via a thoracoscopy
Thoracoscopy
Thoracoscopy is a medical procedure involving internal examination, biopsy, and/or resection of disease or masses within the pleural cavity and thoracic cavity...
approach. The most common approach is the first, or catheter based. In this case the catheter that delivers the ablative energy can use radiofrequency
Radiofrequency ablation
Radio frequency ablation is a medical procedure where part of the electrical conduction system of the heart, tumor or other dysfunctional tissue is ablated using the heat generated from the high frequency alternating current to treat a medical disorder...
, ultrasound, laser or cryothermic energy
Cryoablation
Cryoablation is a process that uses extreme cold to remove tissue .Cryoablation is used in a variety of clinical applications using hollow needles through which cooled, thermally conductive, fluids are circulated...
. The ablative catheter is able to deliver lesions only from its tip, which is from 4 to 8 mm long, shaped like a match point.
The ablation points are centered in the left upper chamber of the heart, or left atrium
Left atrium
The left atrium is one of the four chambers in the human heart. It receives oxygenated blood from the pulmonary veins, and pumps it into the left ventricle, via the mitral valve.-Foramen ovale:...
. A series of ablation points is used to establish a line of lesions. This lines are supposed to block the trigger points of Atrial Fibrillation and create a barrier to the propagation of the arrhythmia. As stated, the lesions target the entrance of the pulmonary veins, of which usually two right and two left ones are found. The lesion points are applied inside the left atrium a few millimeters from the pulmonary vein insertion in the body of the left atrium. This region is known as pulmonary vein antrum . The end point of the procedure is to electrically isolate the pulmonary veins - pulmonary vein isolation or PVI. A less common approach is to encircle both pulmonary vein orifices on one side with a single wider elliptical line, technique called WACA or wide area circumferential ablation. Other lines of lesions and ablation points inside the left and right atrium are often made - mostly on the posterior wall and often also on other targets, such as the coronary sinus
Coronary sinus
The coronary sinus is a collection of veins joined together to form a large vessel that collects blood from the myocardium of the heart. It is present in all mammals, including humans...
, the left atrial appendage base, the superior vena cava
Superior vena cava
The superior vena cava is truly superior, a large diameter, yet short, vein that carries deoxygenated blood from the upper half of the body to the heart's right atrium...
, the right atrial isthmus. Currently, area of complex fragmented signals, called CFAE are also treated with ablation points in order to reduce the risk of recurrent AF. The procedure takes between 2 and 4 hours and occasionally needs to be repeated. As a general rule, older patients with more heart disease and more frequent, longer episodes require more extensive ablation procedures . A technique using a ballon capable of creating lesions all around its perimeter is also being used with less effective results.
Safety
Possible complications are perforation of the posterior wall of the atrium into the esophagusEsophagus
The esophagus is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. During swallowing, food passes from the mouth through the pharynx into the esophagus and travels via peristalsis to the stomach...
, perforation of the free wall with ensuing a strangling collection of blood around the heart, that is known as cardiac tamponade
Cardiac tamponade
Cardiac tamponade, also known as pericardial tamponade, is an emergency condition in which fluid accumulates in the pericardium ....
, a clot flowing from the heart into the brain causing an embolic stroke and narrowing of a pulmonary vein near its insertion in the heart which in the worst case scenario can lead to death of a piece of lung tissue. In experienced centers, the major complication rates should not exceed 2-4%. Currently the procedure is accomplished under anticoagulation with oral and intravenous medications
Efficacy and advantages
After a single procedure, more than 50% of patients with an otherwise normal heart can enjoy freedom from arrhythmias according to studies that have followed patients typically for one year. With 2 or more procedures, the efficacy can be as high as 80-90% in other recent case series.Long term effects and advantages of the procedure are not fully known. In one 5 year study from Germany, most patients remained in normal rhythm after 5 years. Efficacy in patients past their 60's is being studied by an ongoing, long term study, in part sponsored by the US national heart, blood and lung institute. It is advised by leading scientific institutions that anticoagulants could be safely stopped in patients who are taking them because AF increases their risk os stroke a few months after a successful procedure .
Various studies have compared the effects and risks of ablation of Afib versus use of antiaarhythmic drugs All of them have shown that ablation therapy is more effective than antiarrhythmic drugs, in particular in younger patients with a healthy heart and if the ablation is done by highly skilled practitioners.
Alternative techniques
A cure for Atrial Fibrillation can be achieved also with the surgical procedure called Maze or the Minimaze, as described in the History chapter above. This surgical approach can be used as a stand alone surgery, more often in conjunction with otherwise needed cardiac surgery, or a thoracoscopic procedure, that is without the need to open the patient's chest. The surgical procedure can be carried out as a hybrid, that is to say combined with a catheter approachRecommendations
International cardiology societies have issued joint recommendations for the selection of patients suitable to undergo this procedureIn general, to be considered candidates an ablation for AF, patients should be 1 ) symptomatic for the arrhythmia (one of the following symptoms : palpitations, shortness of breath, fatigue and or weakness, dizziness ) 2 ) have tried and failed at last one antiarrhythmic drug, 3) should be free of severe lung disease, 4) should have normal size or mildly dilated atria (upper heart chambers) , 5) normal or mildly reduced cardiac function, Following ablation, most of these patients are free of recurrent AF at least at 1 year or later.
External links
- http://www.hrsonline.org/news/media/press-releases/csablation.cfm From the Heart Rhythm Society online site
- http://www.mayoclinic.com/health/atrial-fibrillation/DS00291 Patient oriented information from the Mayo Clinic
- http://www.heart.org/HEARTORG/Conditions/Arrhythmia/AboutArrhythmia/Atrial-Fibrillation-AF-or-AFib_UCM_302027_Article.jsp#.Tq_jO3LZS58 Patient information on Atrial Fibrillation from the American Heart Association at www.heart.org