What is a wandering baseline on an ECG?

• A. A stable line at baseline
• B. Shift on the ECG tracing from the baseline
• C. A normal P wave
• D. An upward deflection of QRS

Answer: (B)

Wandering baseline occurs when the ECG tracing drifts away from the isoelectric line, causing the tracing to shift up or down rather than stay fixed at zero between waves. This drift is typically due to issues with electrode contact or patient factors, such as movement, poor skin preparation, excess skin oils, or electrodes that aren’t firmly attached. Because the baseline is meant to be relatively flat between waves, any irregular shifting signals a wandering baseline rather than a true cardiac event.

Think of it as a signal quality problem: you’ll see the entire tracing slide rather than remain steady, which can obscure or mimic real electrocardiographic changes. To fix it, ensure good skin prep, clean the area with alcohol, dry the skin, reapply fresh electrodes, and confirm that leads are securely connected and not pulling on the skin. Also check for excessive movement or respiration-related shifts and minimize interference.

The other descriptions don’t fit because a stable line wouldn’t wander, a normal P wave is a specific, small upward deflection representing atrial depolarization, and an upward deflection of the QRS is part of ventricular depolarization, not a drifting baseline.