Normal Daily ECG Changes or Circadian Variations
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Normal Daily ECG Changes or Circadian Variations
Studies have shown day-to-day variations or circadian variations in amplitude, axis, QRS complexes, and T waves on an ECG in the same patient at different times of the day. For example, a young, healthy patient presented with negative deflections of the T wave in precordial leads V3 through V5 between 11 AM and 6 PM but with a normal upward deflection in the T wave throughout the rest of the day.1
1 Willems JL, Poblete PF, Pipberger HV. Day-to-day variation of the normal orthogonal electrocardiogram and vectorcardiogram. Circulation. 1972;45(5):1057–1064.
https://www.ahajournals.org/doi/abs/10.1161/01.CIR.45.5.1057