Left atrial ablation pendulum swinging back towards the pulmonary veins.

No cardiologist today is ignorant anymore of the fact that the pulmonary vein (PV) ostia and the surrounding left atrial (LA) tissue lie at the heart of atrial fibrillation (AF). The PVs may harbor rapidly firing foci that act as triggers for the initiation of paroxysms of AF. Moreover, the region certainly also plays a key role in its perpetuation towards persistent or even permanent forms by harboring fast re-entrant wavelets that maintain the arrhythmia. Since the original reports, describing selective ablation of foci within the PV, ablative strategies have moved towards the ostia and further away from the veins into the left atrium. However, despite intense research, it remains unclear what is the best ablation strategy for AF. Over the last decade, two main ‘schools’ have developed. The first is directed at the electrical isolation of the PV from the left atrium, a goal which is generally achieved by directing RF applications to the ostium of the veins. Therefore, it is referred to as pulmonary vein isolation (PVI). Others have taken a more anatomical approach, encircling the PV with RF lesions. The endpoint of these ablations is less uniform, although attenuation of electrogram amplitude within the ablated region might be used as an endpoint. The latter approach is more diverse among different centres, but as a group, these procedures are referred to as circumferential pulmonary vein ablation (CPVA). A clear superiority for either technique has not emerged from the limited data available comparing the two approaches. Both have in common, however, that 20–58% of the patients have recurrent AF after 6 months to 1 year, despite attaining the procedural endpoint. It is well known that patients with paroxysmal AF have a better outcome than those with persistent/permanent AF, but few other clinical and no procedural identifiers are available to predict the effect of ablation. Recurrences have been attributed to more widespread arrhythmogenic disease, which has led to more elaborate and/or more aggressive ablation approaches with the inclusion of linear lesions, ablation of zones with fractionated electrograms, and/or elimination of vagal ganglionic plexi. Although slightly more effective, the downside of these more aggressive strategies is a higher major complication rate (like fatal LA-oesophageal fistula) or development of LA tachycardia that can be more symptomatic than the original AF and is difficult to ablate. Over the last 2 years, it has become clear that the extent of LA–PV connections is related to arrhythmogenesis, that isolation of all four PVs leads to non-inducibility of AF in a majority of patients, that most recurrences (.80%) are due to re-conduction between a previously isolated PV and the LA, and that repeat isolation results in a reasonable long-term success rate. In fact, the recognition of the importance of PV isolation has resulted in a convergence of both ablation approaches: many groups using CPVA now also assess electrical isolation of the PV, whereas groups relying on PVI apply energy as much as possible outside of the PV ostia to prevent PV stenosis. The question, therefore, is raised in which patients ablation, aimed at PV isolation, might suffice and which characteristics might predict AF recurrence despite complete isolation of all four PVs. Essebag et al. report on behalf of the group of Dr Mark Josephson (Boston) on a series of 102 consecutive patients who were treated with an electrophysiologically guided approach resulting in complete bidirectional isolation of all PVs. On top of ensuring conduction block from LA to PV, they also verified the absence of conduction from PV to LA by elaborate pacing from all 10 to 14 bipoles on a multi-electrode circular catheter positioned in the proximal PV. Interestingly, their study shows that AF inducibility remaining after this isolation is a predictor of recurrent AF, with an odds ratio of 3.84. The study confirms other single-centre reports on the predictive value of non-inducibility of AF after PVI or CPVA with additional lines. The predictive accuracy of AF inducibility is of similar magnitude as that of the type of prior AF (paroxysmal vs. persistent/ permanent). Not only AF induced at baseline but also during infusion of high doses of isoproterenol was predictive. Because 50% of the patients were only induced during isoproterenol administration, these findings indicate that