This is a cohort study to evaluate algorithms for mapping atrial fibrillation by mapping atrial structure and mapping electrical activity to detect physiologically important areas.

A key innovation of the observation study is to assess tracking of physiological activity in AF, in relation to tissue activity (MAP recordings), and in relation to AF waves of activity.

This observational work extends prior studies that focused on focal and rotational activity, dispersion of electrical activity, low voltage activity and others.

In this study, the investigators will compare mapping approaches for atrial fibrillation ablation.

First, investigators will compare approaches to map atrial structure from collected computed tomography (CT) scans or magnetic resonance imaging (MRI) scans acquired routinely in patients undergoing ablation for atrial fibrillation. Imaging will be acquired from a variety of clinically approved

Second, investigators will compare approaches to analyze electrograms collected routinely at clinical electrophysiology study (EPS) in patients undergoing ablation for atrial fibrillation. Electrograms will be recorded from a variety of clinically approved catheters under standard of care conditions, and will be analyzed to better understand the mechanisms for atrial fibrillation and its relationship to outcomes. Electrograms include unipolar recordings, bipolar recordings and, monophasic action potential recordings using FDA-cleared catheters.

The investigators anticipate analyzing data from 1000 patients from inception of the study.

Inclusion Criteria:

• aged 21-80 yrs who underwent electrophysiology study for ablation of Atrial Fibrillation

Exclusion Criteria:

• Poor data quality of recordings of AF

The investigators will study adults aged 21-90 years who have undergone electrophysiology study for ablation of Atrial Fibrillation. De-identified datasets will be made available for comparisons of mapping approaches.