Atrial structure and function and its implications for current and emerging treatments for atrial fibrillation

Left atrial (LA) structure and function are intimately related to the clinical phenotypes of atrial fibrillation (AF), and have direct implications for the success or otherwise of various therapeutic strategies. In conjunction with intrinsic structural characteristics of the LA, pathological remodelling to a large extent dictates the clinical course of AF. Remodelling is a product of the physiological and structural plasticity of the LA in disease states (including AF itself), and manifests as electrical, physical and structural changes that promote the substrate necessary for AF maintenance. The degree of remodelling impacts upon the efficacy of pharmacological, non-pharmacological and interventional treatments for AF. Evolving therapies seek to specifically target these processes although presently, several remain in the development phase. Catheter ablation (CA) is now firmly established as a highly effective treatment for AF, although increasing its efficacy in the remodelled LA of more severe AF phenotypes remains an ongoing challenge

Isolation of the posterior left atrium for patients with persistent atrial fibrillation: routine adenosine challenge for dormant posterior left atrial conduction improves long-term outcome

Aims: Catheter ablation to achieve posterior left atrial wall (PW) isolation may be performed as an adjunct to pulmonary vein isolation (PVI) in patients with persistent atrial fibrillation (AF). We aimed to determine whether routine adenosine challenge for dormant posterior wall conduction improved long-term outcome. Methods and results: A total of 161 patients with persistent AF (mean age 59 +/- 9 years, AF duration 6 +/- 5 years) underwent catheter ablation involving circumferential PVI followed by PW isolation. Posterior left atrial wall isolation was performed with a roof and inferior wall line with the endpoint of bidirectional block. In 54 patients, adenosine 15 mg was sequentially administered to assess reconnection of the pulmonary veins and PW. Sites of transient reconnection were ablated and adenosine was repeated until no further reconnection was present. Holter monitoring was performed at 6 and 12 months to assess for arrhythmia recurrence. Posterior left atrial wall isolation was successfully achieved in 91% of 161 patients (procedure duration 191 +/- 49 min, mean RF time 40 +/- 19 min). Adenosine-induced reconnection of the PW was demonstrated in 17%. The single procedure freedom from recurrent atrial arrhythmia was superior in the adenosine challenge group (65%) vs. no adenosine challenge (40%, P < 0.01) at a mean follow-up of 19 +/- 8 months. After multiple procedures, there was significantly improved freedom from AF between patients with vs. without adenosine PW challenge (85 vs. 65%, P = 0.01).Conclusion Posterior left atrial wall isolation in addition to PVI is a readily achievable ablation strategy in patients with persistent AF. Routine adenosine challenge for dormant posterior wall conduction was associated with an improvement in the success of catheter ablation for persistent AF