Table 1.

Demographic and clinical characteristics of the development and external validation data sets

	MHI All-Comers	MHI Hospitalized	MHI Biobank	MIMIC-IV
ECG	669 782	475 986	104 850	437 323
Patients	145 323	76 680	11 622	109 870
ECG per patient	2.0 (Q1: 1.0, Q3: 5.0)	3.0 (Q1: 2.0, Q3: 8.0)	6.0 (Q1: 3.0, Q3: 12.0)	2.0 (Q1: 1.0, Q3: 4.0)
Patient-level data
Age (years)	61.3 (± 15.2)	64.3 (± 13.7)	63.2 (± 11.6)	59.2 (± 17.9)
Male	84 087 (57.9%)	50 114 (65.4%)	7326 (63.0%)	51 627 (47%)
CIMD	3.2 (± 1.4)	3.2 (± 1.3)	3.2 (± 1.4)
MHI Hospitalized	76 680 (52.8%)	76 680 (100.0%)	7919 (68.1%)
Follow-up (years)	3.2 (Q1: .3, Q3: 8.6)	4.0 (Q1: .3, Q3: 9.7)	9.6 (Q1: 4.6, Q3: 13.6)	1.1 (Q1: .03, Q3: 4.7)
5-year incident AF	22 695 (15.6%)	18 492 (24.1%)	2846 (24.5%)	16 610 (15.1%)
ECG-level data
Age (years)	62.8 (± 14.8)	64.2 (± 14.1)	64.0 (± 12.0)	61.2 (± 16.5)
Follow-up (years)	4.2 (Q1: 1.2, Q3: 8.3)	4.3 (Q1: 1.1, Q3: 8.6)	6.6 (Q1: 3.2, Q3: 10.5)	1.7 (Q1: .2, Q3: 4.5)
5-year incident AF	80 183 (12.0%)	70 230 (14.8%)	13 772 (13.1%)	65 301 (14.9%)
Years to incident AF	2.0 (Q1: .1, Q3: 5.6)	1.9 (Q1: .1, Q3: 5.5)	3.3 (Q1: .7, Q3: 7.0)	1.1 (Q1: .1, Q3: 3.3)

‘MHI All-Comers’ group includes all the development set electrocardiograms. ‘MHI Hospitalized’ group includes the electrocardiograms of patients who have been hospitalized at the MHI. ‘MHI Biobank’ includes the subset of patients in the Montreal Heart Institute hospital biobank. ‘MIMIC-IV’ includes all eligible patients and electrocardiograms of the external validation data set. The number of electrocardiograms per patient, follow-up duration, and time to incident atrial fibrillation are provided in quartiles format, indicating the median, 25th percentile (Q1), and 75th percentile (Q3). Age and Canadian Index for Multiple Deprivation (CIMD) are presented as mean ± standard deviation.