Invited Commentary

Abstract

Although the majority of the patients with paroxysmal atrial fibrillation (AF) can be successfully treated by surgical or catheter-based pulmonary vein (PV) isolation, the success rate of the PV isolation alone for persistent or longstanding persistent AF has been unsatisfactory. It has been demonstrated that the repetitive activations arising from the PV or other regions act as a trigger, and a substrate in the atrium is required for the perpetuation of AF [1Nitta T. Ishii Y. Miyagi Y. et al.Concurrent multiple left atrial focal activations with fibrillatory conduction and right atrial focal or reentrant activation as the mechanism in atrial fibrillation.J Thorac Cardiovasc Surg. 2004; 127: 770-778Abstract Full Text Full Text PDF PubMed Scopus (89) Google Scholar]. The substrate may include slow conduction, dispersion of refractoriness, or non-PV abnormal activations. The multiple atrial incisions of the maze procedure may disrupt the substrate, resulting in a highly frequent conversion rate of AF back to sinus rhythm, even in longstanding persistent AF. Recent findings during catheter-based PV isolation have demonstrated that the PV-LA junction provides a unique electrophysiologic environment for sustaining re-entry [2Kumagai K. Ogama M. Noguchi H. et al.Electrophysiologic properties of pulmonary veins assessed using a multielectrode basket catheter.J Am Coll Cardiol. 2004; 43: 2281-2289Abstract Full Text Full Text PDF PubMed Scopus (154) Google Scholar]. The PV-LA region has heterogeneous electrophysiologic properties that allow preferential and re-entrant activation within the PV and at the PV-LA junction. Based on the findings during catheter ablation of AF, Haïssaguerre and colleagues [3Haïssaguerre M. Sanders P. Hocini M. et al.Pulmonary veins in the substrate for atrial fibrillation: the “venous wave” hypothesis.J Am Coll Cardiol. 2004; 43: 2290-2292Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar] proposed a new concept of AF, a venous wave hypothesis, in which the anatomical and electrophysiological structures around the PV-LA junction are implicated not only as triggers of AF, but also as a source of “venous waves/drivers” that are capable of maintaining AF. In a study reported in this issue of The Annals of Thoracic Surgery, Li and colleagues [4Li H. Li Y. Sun L. et al.Minimally invasive surgical pulmonary vein isolation alone for persistent atrial fibrillation: preliminary results of epicardial atrial electrogram analysis.Ann Thorac Surg. 2008; 86: 1219-1226Abstract Full Text Full Text PDF PubMed Scopus (17) Google Scholar] focused on this exciting and unresolved issue. They recorded bipolar electrograms from the PVs, proximal antrum, and proximal LA, and compared the morphologies of the electrograms and AF cycle length before and after the PV isolation in patients with persistent AF. The AF cycle length at the PVs was shorter than that at the proximal LA and the activation sequence at the PV-LA region was from the proximal LA to the PV. The larger the LA diameter, the longer the AF cycle length was at the proximal LA. The PV isolation resulted in prolongation of the AF cycle length at the LA, and the prolongation was less in patients that had recurrent AF postoperatively. These findings are similar to those during catheter ablation [5Haïssaguerre M. Sanders P. Hocini M. et al.Changes in atrial fibrillation cycle length and inducibility during catheter ablation and their relation to outcome.Circulation. 2004; 109: 3007-3013Crossref PubMed Scopus (343) Google Scholar]. A progressive and cumulative increase in the AF cycle length after the PV isolation was demonstrated with the magnitude of the increase correlating with the termination of the AF and prevention of the inducibility. Although the maze procedure provides a consistent and highly frequent conversion rate of AF, the mechanism of AF does not seem to be as simple as we believed. Critical regions for maintaining AF should shift from the PV to the PV-LA junction, and further to the LA and RA, as the mode of the AF degenerates from paroxysmal to persistent or longstanding persistent AF. The other finding [6Nademanee K. McKenzie J. Kosar E. et al.A new approach for catheter ablation of atrial fibrillation: mapping of the electrophysiologic substrate.J Am Coll Cardiol. 2004; 43: 2044-2053Abstract Full Text Full Text PDF PubMed Scopus (1655) Google Scholar] during catheter ablation that ablation of the region where complex fractionated electrograms were recorded, terminated persistent AF without any isolation of the PVs suggests that PV isolation is no longer the primary lesion set in the surgical treatment of persistent AF. Minimally Invasive Surgical Pulmonary Vein Isolation Alone for Persistent Atrial Fibrillation: Preliminary Results of Epicardial Atrial Electrogram AnalysisThe Annals of Thoracic SurgeryVol. 86Issue 4PreviewMinimally invasive surgical pulmonary vein isolation has become an alterative therapy for lone atrial fibrillation. This study evaluated the effect of the procedure on persistent atrial fibrillation by epicardial atrial electrography. Full-Text PDF