The following are 10 points to remember from this review of atrial fibrosis as a potential guide for ablation of atrial fibrillation (AF):

1. There often is discordance between the AF duration and burden and the amount of atrial fibrosis.
2. It is likely that the extensive biatrial fibrosis that can be found in some patients early on in the course of their AF is a result of fibrotic atrial cardiomyopathy (FACM).
3. The degree of FACM could explain why some patients have a low burden of paroxysmal AF for many years, whereas other patients go directly into persistent AF without ever having paroxysmal AF.
4. Well-demarcated areas of marked fibrosis are more commonly found than a pattern of diffuse severe fibrosis.
5. Atrial fibrosis is a major predictor of recurrent AF in patients who have undergone pulmonary vein isolation (PVI).
6. The fibrotic substrate can be used to design a tailored AF ablation strategy.
7. This approach requires voltage mapping during sinus rhythm using an electroanatomical mapping system.
8. The following classification system for fibrosis is proposed: severe, <0.5 mV; mild/moderate, 0.5-1.5 mV; normal, >1.5 mV. Scar is defined by the absence of discrete electrograms and local capture during pacing.
9. A fibrosis-guided ablation strategy consists of circumferential PVI followed by circumferential isolation of regions of severe fibrosis, then ablation lines connecting these regions to the PVI lines.
10. The early experience with fibrosis-guided ablation of AF suggests that it improves efficacy compared with PVI by itself. However, randomized clinical trials are needed to demonstrate the incremental clinical value of this approach.

Keywords: Arrhythmias, Cardiac, Atrial Fibrillation, Cardiomyopathies, Catheter Ablation, Fibrosis, Heart Atria, Pacemaker, Artificial, Pulmonary Veins, Secondary Prevention

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