Do signal-averaged electrocardiograms (SAECGs) exhibit a heart rate-dependent diurnal variation in healthy subjects?
Signal-averaged ECG parameters exhibit significant diurnal variation that is closely related to changes in heart rate, which should be considered when interpreting these tests.
It has not been determined if signal-averaged electrocardiograms (SAECGs) have a diurnal variation. We recorded 3-channel 24-hour ECGs in 30 healthy volunteers and calculated the following parameters for the first 500 sec of every hour over the 24-hour period: the mean heart rate, the filtered QRS duration (f-QRS), the root-mean-square voltage of the signals in the last 40 msec of the QRS (RMS40), and the duration of low-amplitude signals (< 40 microV) in the terminal portion of the QRS (LAS40). Heart rate and RMS40 increased in the daytime compared with the nighttime; f-QRS and LAS40 increased during the nighttime hours. The f-QRS and LAS40 were negatively correlated with heart rate in all and 22 (73%) of 30 subjects, respectively, and RMS40 was positively correlated with heart rate in 21 subjects (70%). In conclusion, SAECGs exhibit a clear diurnal variation in healthy subjects, which is closely related to changes in heart rate.
Nakagawa et al. (Thu,) studied this question.
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