All ECGs were processed by the Modular ECG Analysis
System (MEANS) [17]. MEANS has extensively been
evaluated both by its developers [17] and by others
[18,19]. In the latter studies, the MEANS measurements
were gauged against those obtained from a panel of
cardiologists, proving their accuracy and stability. Also in
comparison to other programs MEANS scored among the
best. The interval measurements are lead-independent, i.e.,
they make use of the common wave onsets and offsets of the
12 simultaneous leads together. The morphological measurements
are lead-dependent, i.e., they are taken per lead
from one averaged representative complex. A wave within a
complex is counted as present if it has both an amplitude of at
least 0.025 mV and a duration of at least 8 ms.