—Our goal was to investigate the effect of a global XYZ median beat construction and
the heart vector origin point definition on predictive accuracy of ECG biomarkers
of sudden cardiac death (SCD). —Atherosclerosis Risk In Community study participants
with analyzable digital ECGs were included (n=15,768; 55% female, 73% white, mean
age 54.2±5.8 y). We developed an algorithm to automatically detect the heart vector
origin point on a median beat. Three different approaches to construct a global XYZ
beat and two methods to locate origin point were compared. Global electrical heterogeneity
was measured by sum absolute QRST integral (SAI QRST), spatial QRS-T angle, and spatial
ventricular gradient (SVG) magnitude, azimuth, and elevation. Adjudicated SCD served
as the primary outcome. —There was high intra-observer (kappa 0.972) and inter-observer
(kappa 0.984) agreement in a heart vector origin definition between an automated algorithm
and a human. QRS was wider in a median beat that was constructed using R-peak alignment
than in time-coherent beat (88.1±16.7 vs. 83.7±15.9 ms; P<0.0001), and on a median
beat constructed using QRS-onset as a zeroed baseline, vs. isoelectric origin point
(86.7±15.9 vs. 83.7±15.9 ms; P<0.0001). ROC AUC was significantly larger for QRS,
QT, peak QRS-T angle, SVG elevation, and SAI QRST if measured on a time-coherent median
beat, and for SAI QRST and SVG magnitude if measured on a median beat using isoelectric
origin point. —Time-coherent global XYZ median beat with physiologically meaningful
definition of the heart vector’s origin point improved predictive accuracy of SCD
biomarkers.