User manual

How the M2662A Measures ECGs
3-3
November 27, 2000 8:59 am DRAFT
Chapter 3
Understanding ECG
Measurements
3Waveform Recognition
The first step of the measurement program involves waveform recognition and beat
detection. A boundary indicator waveform in which QRS complexes and pacemaker
spikes are enhanced is derived from all leads over the ten-second analysis period.
After the approximate QRS complex and pacemaker spike locations are known,
another boundary indicator waveform that enhances P and T wave detection is
derived. Approximate P wave, QRS complex and T wave regions are then
determined for each beat in the ECG.
3Comprehensive Measurements
After the approximate waveform locations are known, they are further refined to
determine precise onsets and offsets for each waveform. Once onsets and offsets are
known, amplitude, duration, area and shape are calculated for every P wave, QRS
complex, T wave and ST segment in every lead that you see on the Auto 3 x 4
report. Waveform irregularities such as notches, slurs, delta waves and pacemaker
spikes are also noted for every beat.
3Group Measurements
After all the beats have been measured, each beat in the ECG is classified into one
of five rhythm groups based on rate and morphology parameters. Each group
consists of beats with similar R-R intervals, durations, and shapes, except that all
paced beats are grouped together, regardless of other parameters. Group 1 represents
the type of beat that is most normal or predominant and groups 2 through 5 represent
other beat types. Group measurements are calculated by averaging the
measurements for all the leads in each of the groups.
3Lead Measurements
Representative measurements for each of the 12 leads are calculated from the
comprehensive set of measurements for all the beats in the ECG. Only the beats of
the predominant group (Group 1) are used. If a particular lead (as shown on the Auto
3 x 4 report) does not have any Group 1 beats, a beat group with similar parameters
is used, if possible. The measurement program tries to select a beat group for which
the beats are not paced. Only if all beats in the ECG are paced will the
measurements be for paced beats. If there are paced and non-paced beats in an ECG,
only the non-paced beats will be measured, which may result in leads for which no
measurements are reported.