Ablation of atrial fibrillation

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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 veins, which are the veins that bring oxygenated blood from the lungs back to the left side of the heart.

Contents

History

In 1987, Dr. James Cox 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.[1]

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 stroke, heart failure and increased risk of death.[2] 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").[3] 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 currently 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 surgery 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.[4] A technique using a cyoablation ballon capable of creating lesions all around its perimeter is also being used with comparable results in patients with paroxysmal atrial fibrillation.

Safety

Possible complications are perforation of the posterior wall of the atrium into the esophagus, 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 [5]

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 two 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.[6] Efficacy in patients past their 60's is being studied by an ongoing, long term study,[7] 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 of stroke a few months after a successful procedure.[8] Various studies have compared the effects and risks of ablation of Afib versus use of antiarrhythmic drugs[9] 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 approach [10]

Recommendations

International cardiology societies have issued joint recommendations for the selection of patients suitable to undergo this procedure [2][8] 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 least 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.

References

  1. ^ Jais P, Haissaguerre M, Shah DPDC et al. A focal source of atrial fibrillation treated by discrete radiofrequency ablation. Circ 1997;95:572-76
  2. ^ a b Fuster V, Rydén LE, Cannom DS et al. (2006). "ACC/AHA/ESC 2006 Guidelines for the Management of Patients with Atrial Fibrillation: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Revise the 2001 Guidelines for the Management of Patients With Atrial Fibrillation): developed in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society". Circulation 114 (7): e257–354
  3. ^ Anti-arrhythmic drug therapy for atrial fibrillation: current anti-arrhythmic drugs, investigational agents, and innovative approaches Irina Savelieva and John CammEuropace (2008) 10 (6): 647-665
  4. ^ About.com
  5. ^ Updated Worldwide Survey on the Methods, Efficacy, and Safety of Catheter Ablation for Human Atrial Fibrillation. Riccardo Cappato, MD, Hugh Calkins, MD, Shih-Ann ChenCirculation: Arrhythmia and Electrophysiology. 2010; 3:
  6. ^ Long-Term Results of Catheter Ablation in Paroxysmal Atrial Fibrillation: Lessons From a 5-Year Follow-Up. Feifan Ouyang, Roland Tilz, Julian Chun, Boris Schmidt, Erik Wissner, Thomas Zerm, Kars Neven, Bulent Köktürk, Melanie Konstantinidou, Andreas Metzner, Alexander Fuernkranz, and Karl-Heinz Kuck Circulation. 2010;122:2368-2377
  7. ^ Cabana Trial
  8. ^ a b Wann LS, Curtis AB, January CT 2011 ACCF/AHA/HRS Focused Update on the Management of Patients With Atrial Fibrillation (Updating the 2006 Guideline) A Report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice GuidelinesJ Am Coll Cardiol, 2011; 57:223-242
  9. ^ Comparing Antiarrhythmic Drugs and Catheter Ablation for Treatment of Atrial Fibrillation. David J. Callans. Circulation 2008; 118: 2488-2490
  10. ^ New Technologies in Atrial Fibrillation Ablation. Burkhardt JD, Natale,A. Circulation. 2009; 120: 1533-1541

External links