EKG AcquisitionQuestion 60 of 100
On a 12-lead tracing, leads I, II, and aVR are clean, but lead III alone shows an erratic, noisy trace. What is the most likely cause?
a.The patient is having a myocardial infarction affecting only the inferior wall
b.The paper speed is incorrect
c.A single electrode or lead wire connection is loose or dried out
d.Alternating current interference from the room lighting
Explanation
Artifact confined to one lead points to a problem with a specific electrode or lead wire, since each limb lead uses a different combination of electrodes; the fix is to reapply that electrode and reseat the wire. A true infarction produces recognizable ST or Q wave changes across a group of leads rather than random noise. Paper speed errors and AC interference affect the entire tracing, not one lead.
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