This database includes 25 long-term ECG recordings of human subjects with atrial fibrillation (mostly paroxysmal).

Of these, 23 records include the two ECG signals (in the .dat files); records 00735 and 03665 are represented only by the rhythm (.atr) and unaudited beat (.qrs annotation files.

The individual recordings are each 10 hours in duration, and contain two ECG signals each sampled at 250 samples per second with 12-bit resolution over a range of ±10 millivolts. The original analog recordings were made at Boston's Beth Israel Hospital (now the Beth Israel Deaconess Medical Center) using ambulatory ECG recorders with a typical recording bandwidth of approximately 0.1 Hz to 40 Hz. The rhythm annotation files (with the suffix .atr) were prepared manually; these contain rhythm annotations of types (AFIB (atrial fibrillation), (AFL (atrial flutter), (J (AV junctional rhythm), and (N (used to indicate all other rhythms). (The original rhythm annotation files, still available in the old directory, used AF, AFL, J, and N to mark these rhythms; the atr annotations in this directory have been revised for consistency with those used for the MIT-BIH Arrhythmia Database.) Beat annotation files (with the suffix .qrs) were prepared using an automated detector and have not been corrected manually. For some records, manually corrected beat annotation files (with the suffix .qrsc) are available. (The .qrs annotations may be useful for studies of methods for automated AF detection, where such methods must be robust with respect to typical QRS detection errors. The .qrsc annotations may be preferred for basic studies of AF itself, where QRS detection errors would be confounding.) Note that in both .qrs and .qrsc files, no distinction is made among beat types (all beats are labelled as if normal).