Therapeutic Approaches to Atrial Fibrillation Ablation Targeting Atrial Fibrosis.

Atrial fibrosis is the fundamental histopathologic finding in atrial fibrillation (AF) patients and an important predictor of ablation failure beyond pulmonary vein isolation. There is wide variation in the extent and localization of left atrial fibrosis in patients with paroxysmal and nonparoxysmal AF. Box isolation of fibrotic areas is an effective rhythm control concept in patients with paroxysmal AF despite durable pulmonary vein isolation, and this strategy has recently been implemented successfully in initial AF ablation procedures in addition to pulmonary vein isolation for patients with nonparoxysmal AF. In contrast, the time for "empirical" lines or other nonindividualized substrate modifications seems over.