Dear betty,
An undulating or moving baseline is usually due to technical factors in the ECG recording and has nothing to do with the individual's heart rhythm itself. Ways to decrease this effect during the recording include remaining completely still during the recording, not breathing or breathing very shallow, not using lotions the day prior to the ECG, prepping the skin with alcohol prep pads and sandpaper tape prior to attaching the electrodes, proper lead placement and making sure the patient is electrically isolated during the recording.