The ECG Module is a single ECG lead (uses 3 electrodes) system, and when
used with surface leads attached as directed, the ECG waveform is Lead II
and is used for HR calculation. When used with the esophageal electrodes
the lead is similar to a Lead II, but it is better referred to as simply the
Esophageal Lead since it is not identical to a surface ECG lead II.
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