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Updated: Mar 25, 2026

Patient-specific Modeling of the Heart: Estimation of Ventricular Fiber Orientations
Published on: January 8, 2013
Beat-to-beat determinants of the beat-to-beat temporal and spatial variability of repolarization
Albert Feeny1, Larisa G Tereshchenko2
1Whiting School of Engineering, Johns Hopkins University, Baltimore, MD, USA.
Background:
The goal of this study was to compare the time series predictors of beat-to-beat variability in repolarization in healthy individuals.
Methods:
Spatial QRS- and T-vector amplitudes, spatial QRS-T, RR' and TT' angles, RR' and QT intervals, and QRS- and T-loop roundness were measured on 453 consecutive sinus beats in 168 healthy subjects (mean age 39.8±15.6years; 50% men; 93% white). Panel time-series regression models were adjusted by age, sex, and race. Appropriate time series of ECG metrics served as predictors and outcomes.
Results:
Increase in T-loop roundness index by 0.1 was associated with 1.1° (95%CI 0.9-2.2; P=0.048) increase in corresponding TT' angle. One unit increase in a respiration index was associated with 4ms (95%CI 0.6-7.0; P=0.021) increase in QT interval.
Conclusions:
Spatial TT' angle and beat-to-beat variability in T-loop roundness represent intrinsic measures of repolarization variability. QT interval variability characterizes the effect of respiration and heart rate variability.
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