Catheter Ablation of Non-pulmonary Vein Foci
Since the discovery of the role of the pulmonary veins (PVs) in the initiating process of atrial fibrillation (AF), it has been known that a minority of ectopic beats initiating AF arise from non-PV regions. The elimination of such non-PV foci is critical
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19
Yoshihide Takahashi
Keywords
Non-PV foci • Non-contact mapping • Isoproterenol • PLSVC • Ligament of Marshall
19.1 Introduction Mapping of atrial fibrillation (AF) is challenging because of a chaotic atrial activation. Thus, the mechanism of AF remains to be elucidated. On the other hand, mapping of the initiating process of AF is feasible because the local activation time during the initiating beat can be determined. Haissaguerre et al. performed mapping of the initiating beat and discovered the role of the pulmonary veins (PVs) in the late 1990s [1]. In their first report of mapping initiating beats, it was described that a major source of the initiating beats came from the PVs, but a minority arose from non-PV regions. It was demonstrated that the presence of non-PV foci is associated with arrhythmia recurrence after catheter ablation, and the elimination of the non-PV foci improves the clinical outcome [2, 3]. Thus, mapping and ablation of non-PV foci is essential for the catheter ablation of AF.
19.2 Electrophysiological Characteristics 19.2.1 Provocation of Ectopic Beats If ectopic beats constantly occur during the ablation procedure, the ectopic beats are readily mapped and successfully eliminated. However, that is not always the case. Y. Takahashi, M.D. The Department of Cardiovascular Medicine, Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-ku, Tokyo 113-8510, Japan e-mail: [email protected]
Provocation of ectopic beats is usually required. The administration of isoproterenol is commonly used and effective in provoking ectopic beats. Particularly, foci in the ligament of Marshall are sensitive to the administration of isoproterenol [4]. Therefore, when ectopic beats occur after the administration of isoproterenol, mapping should be performed first in the coronary sinus (CS) and lateral the left atrium (LA). Ectopic beats often occur after electrical cardioversion of spontaneous or induced AF. In patients in sinus rhythm, an administration of isoproterenol with a target heart rate of 120 bpm and atrial burst pacing with a cycle length of 250 ms down to 180 ms is performed to induce AF. After induction of AF, sinus rhythm is restored by electrical cardioversion. The administration of adenosine triphosphate is also effective in provoking ectopic beats. This test is effective to induce ectopic beats from the PVs and superior vena cava (SVC) rather than atrial foci. This may be associated with the sensitivity of the PV or SVC myocardium to autonomic modulation [5, 6]. The administration of adenosine triphosphate is commonly performed to identify any dormant conduction from the PVs. If ectopic beats occur during the administration of adenosine triphosphate, we firstly consider a conduction recovery between the PVs and LA or SVC foci. Additionally, we need to remember that catheter-induced ectopic beats are likely to occur during the above-mentioned provocation test due to the hyperdynamic state. A mapping catheter is often inserted from the jugular vein, which can cause c
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