A second weakness of the older studies is that
the ECG recording equipment was generally not up to
modern standards in terms of bandwidth or sampling
frequency, as a consequence of which ECG amplitudes
are liable to have been underestimated. In the third place,
anthropometric factors change over time and may render
normal values that were established long ago less
applicable. A fourth limitation is that many studies,
among them the most recent ones, focus on a limited set
of parameters [7,8], or even on only one single specific
measurement, e.g. QT-interval duration [6] or QRS-T angle
[9]. A fifth objection is that ECGs, although taken from
normal subjects, were sometimes excluded on the sole
ground that they were deemed to be abnormal by the
investigators [7]. Lastly, the study population is often small,
may contain subjects of only one sex, may not include all age groups and in particular suffers from a scarcity of
subjects of advanced age.
A second weakness of the older studies is that
the ECG recording equipment was generally not up to
modern standards in terms of bandwidth or sampling
frequency, as a consequence of which ECG amplitudes
are liable to have been underestimated. In the third place,
anthropometric factors change over time and may render
normal values that were established long ago less
applicable. A fourth limitation is that many studies,
among them the most recent ones, focus on a limited set
of parameters [7,8], or even on only one single specific
measurement, e.g. QT-interval duration [6] or QRS-T angle
[9]. A fifth objection is that ECGs, although taken from
normal subjects, were sometimes excluded on the sole
ground that they were deemed to be abnormal by the
investigators [7]. Lastly, the study population is often small,
may contain subjects of only one sex, may not include all age groups and in particular suffers from a scarcity of
subjects of advanced age.
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