Page 21 - ADD-ON ABLATION SURGERY IN PATIENTS WITH ATRIAL FIBRILLATION

Catheter ablation
Multiple approaches have been developed for catheter ablation, all aimed at eliminating 1 mechanisms in the initiation and maintenance of AF. A complete isolation of the PVs
and application of the lesion set proximal to the junction of the left atrium and tube-
like portion of the PV are considered necessary by most techniques.
The different approaches proposed for catheter ablation include: a) Segmental/ ostial PV isolation; b) Circumferential PV ablation; c) Circumferential/antral PV isolation; d) Electrogram-based ablation or complex fractionated atrial electrograms (CFAEs) ablation; e) Linear lesions; f) Autonomic ganglionated plexi ablation; g) Ablation of AF Nest; h) Sequential ablation strategy.
Segmental PV isolation requires ablation inside the vein or very close to the output into the atrium108. It is accepted that ablation in the PVs needs to be avoided thus an extensive atrial ablation, often circumferential is carried out with a trans-septal circular mapping catheter placed at the ostia of the four PVs 108 which creates a series of segmental lesions until isolation of the vein can be demonstrated. Circumferential PV ablation has been widely employed 109-110. Over time the lesion set has been modified with wider circumferential lesions (1-2 cm outside PV ostia) by adding posterior lines connecting PVs and the mitral isthmus line and, finally, by abolishing the evoked vagal reflexes, in order to prevent recurrences of atrial tachycardia111-112.
Circumferential PV isolation can be monitored by various tools, according to operator preference.Selective pulmonary venography is widely employed to define the relevant anatomy. Intracardiac echocardiography (ICE), computerized mapping and navigation techniques (Carto, NaviX, etc) help to define anatomy and catheter guidance. Registration with other techniques such as magnetic resonance (MR) or computed tomography (CT) facilitates a more accurate anatomical definition. However, the critical goal of all these techniques is to ensure that the lesion is made outside the PVs66. Some investigators have extended the PV isolation concept to include ablation of the PV antrum113 which, combined with spectral mapping, has been demonstrated to improve AF success in patients with long- lasting persistent AF114. CFAE ablation, instead of ablating sites in the pulmonary veins, targets sites in specific areas of the atria where the electrograms break up (become fractionated) 115. These ablation sites are determined on an individual patient basis, offering a customized and often reduced area of treatment. Linear lesions are generally deployed at the LA roof and /or at the mitral isthmus116-117. Their goal is to create a bidirectional block and they have been demonstrated
Introduction
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