Background and aims Although electrical activity of the normal human heart is well-characterized by the 12-lead electrocardiogram, detailed insights into within-subject and between-subject variations of ventricular activation and recovery by noninvasive electroanatomic mapping are lacking. We characterized human epicardial activation and recovery within and between normal subjects using noninvasive electrocardiographic imaging (ECGI) as a basis to better understand pathology. Methods Epicardial activation and recovery were assessed by ECGI in 22 normal subjects, 4 subjects with bundle branch block (BBB) and 4 with long-QT syndrome (LQTS). We compared characteristics between the ventricles (LV versus RV), sexes and age groups (<50y/≥50y (years)). Pearson's correlation coefficient (CC) was used for within-subject and between-subject comparisons. Results Age of normal subjects averaged 49+/-14 years, 6/22 were male, and no structural/electrical heart disease was present. Average activation time was longer in LV than in RV, but not different by sex or age. Electrical recovery was similar for the ventricles, but started earlier and was on average shorter in males than females. Median CCs of between-subject comparisons of the ECG signals, activation and recovery patterns were 0.61, 0.32 and 0.19, respectively. Within-subject beat-to-beat comparisons yielded higher CCs (0.98, 0.89 and 0.82, respectively). Activation and/or recovery patterns of patients with BBB or LQTS contrasted significantly with those found in the normal population. Conclusion Activation and recovery patterns vary profoundly between normal subjects, but are stable individually beat to beat, with a male preponderance to shorter recovery. Individual characterization by ECGI at baseline serves as reference to better understand the emergence, progression and treatment of electrical heart disease.

M.J.M.C. is part-time employed by Philips Research.

This work was supported by the Special Research Fund (BOF) of Hasselt University and Maastricht University Medical Center (MUMC+) [BOF17DOCMA15 to J.S.]; the Netherlands CardioVascular Research Initiative [CVON2017-13 VIGILANCE to J.S., B.v.R. and P.G.A.V., and CVON2018B030 PREDICT2 to P.G.A.V.]; a Kootstra Talent Fellowship research grant from Maastricht University [2015T61 to U.C.N.]; the German Academic Scholarship Foundation and the Walter Benjamin Programme by the German Research Foundation [DFG, 529532291 to P.M.D.]; the Dutch Heart Foundation [2021T016 to U.C.N.]; The Netherlands Organization for Scientific Research [(ZonMw (0915016181013)) to R.t.B. and TTW16772 to M.J.M.C.]; and the Health Foundation Limburg (Maastricht, The Netherlands) [to M.J.M.C].

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Ethics committee of Maastricht University Medical Center+ (MUMC+), The Netherlands gave ethical approval for this work (METC 11-2-043). Ethics committee of Health Research Authority London, United Kingdom (Surrey; 19/LO/0762) gave ethical approval for this work

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