How to perform pulmonary vein isolation for the treatment of atrial fibrillation: use of the LocaLisa catheter navigation system

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Abstract
Atrial fibrillation (AF) is the most prevalent supraventricular arrhythmia in man; its treatment is a major challenge to clinicians. The concept of focally induced AF due to ectopy from the pulmonary veins (PV) has revolutionised the approach to non-pharmacological therapy [1]. Prospective studies and reliable markers for the identification of patients most likely to benefit are lacking; in particular, it is unclear how many patients with paroxysmal AF actually have a (PV-related) focal mechanism. Short-term results of pulmonary vein isolation (PVI) in selected groups of patients are, however, highly promising. Conceptually speaking, the approach to PVI can be divided into two schools. In the more focus-driven/segmental method according to Haïssaguerre et al., radiofrequency (RF) lesions are applied slightly distal to the PV ostia to induce electrical isolation of the muscular sleeves of the PV (and associated arrhythmogenic foci) from the left atrium [2]. This method has since evolved to entail lesions just outside the PV ostia, and include additional lines of block between the left inferior PV and mitral annulus, and between the two superior PVs. This in effect brings it closer to Pappone et al.'s approach (described below) than the original ectopy-driven approach first described by Haïssaguerre et al. All four veins are generally targeted. In most cases, segmental ablation induces total electrical isolation, obviating the need for circumferential ablation. This may conceivably reduce the risk of PV stenosis, one of the most serious complications reported following PVI, while lowering the number of RF deliveries and screening time. In the approach according to Pappone et al. [3], reminiscent of the surgical Maze procedure, the left and right PV ostia are circumferentially isolated from the left atrium en bloc, and the left circle connected with the mitral annulus. Reduction of bipolar electrograms to 0.1 mV or less within the lesion and more than 30 ms delay in activation timing either side of the line of conduction block were reported end-points. In either method, meticulous catheter positioning relative to the PV ostia and creation of contiguous lines or areas of lesion are of utmost importance. The LocaLisa system (Medtronic, Minneapolis, MN) has been previously described [4], and its use in catheter navigation and ablation for a variety of indications has been demonstrated. The system allows real-time three-dimensional visualisation of catheter position, including the Lasso catheter (Biosense Webster, Diamond Bar, CA) used to record PV potentials at the ostium during PVI, reducing fluoroscopy time [5]. The following case demonstrates the use of the LocaLisa system in RF ablation for PVI in the treatment of paroxysmal AF.

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