The Substrate in AF

The atrial substrate has been variably defined, and represents an umbrella term encompassing the spectrum of alterations in the electrical properties of the atria associated with AF. A panoply of remodeling phenomena have been described in experimental models and clinical studies, and while it remains unclear to what extent each is a cause or consequence of AF, many possess the potential to facilitate reentry and thus perpetuate AF. Classically these maladaptive remodeling processes have been categorized as electrical changes evident at the cellular level, or structural remodeling at the tissue level. Much of the recent focus has been on the latter and in particular the deposition of fibrotic tissue within the atrial landscape, perhaps reflecting the perception of this representing a more advanced and potentially irreversible stage of the arrhythmogenic process.