Atrial fibrosis in atrial fibrillation: Mechanisms, mapping techniques and clinical applications

Atrial fibrosis plays a pivotal role in the initiation and progression of atrial fibrillation (AF), creating a substrate for AF through structural, electrical and functional remodelling. Atrial remodelling results from various factors, including inflammation, obesity, hypertension and ischaemia, which collectively disrupt cellular coupling and ion channel function. The heterogeneity formed by the distribution of atrial fibrosis creates a substrate for abnormal electrical propagation and arrhythmias through alterations in ionic currents and conduction slowing. The extent of atrial fibrosis may be investigated through multiple modalities, including imaging and electroanatomic mapping. The pathological processes underlying atrial fibrosis are exacerbated in the transition from paroxysmal to persistent AF, highlighting the need for advanced diagnostic and therapeutic strategies. In this review, we cover the role of atrial fibrosis in AF, evaluate the modalities used to quantify and characterize atrial fibrosis, giving an overview of their clinical applications in stratifying patients and guiding treatment strategies, and discuss the integration of fibrosis information in computational AF models. We explore how the combination of experimental and computational techniques can enhance our understanding of the arrhythmogenic effects of fibrosis and the challenges inherent in translating mechanistic insights into effective therapies.