EKG and Diagnostic Testing: Lead Placement and Artifact Control
Core concepts
EKG questions test correct setup, recognition of artifact, and safe handling of the tracing. Know the standard 12-lead placement: limb leads on the arms and legs (RA, LA, RL, LL), and precordial leads V1 through V6 across the chest. V1 sits at the fourth intercostal space at the right sternal border; V2 mirrors it on the left; V4 is at the fifth intercostal space at the midclavicular line; V3 sits between V2 and V4; V5 and V6 follow at the anterior and midaxillary lines. Place limb electrodes on fleshy areas, not bone, and ensure good skin contact.
Recognize common artifact: baseline wander from movement or breathing, muscle tremor from shivering, and 60-cycle interference from nearby electrical equipment. Interventions: keep the patient still and warm, remove nearby electrical devices, check electrode adhesion, and reapply. Know that a normal EKG does not rule out problems, and that you report findings rather than interpret them to the patient.
Traps
Questions swap V1 and V2 or place V4 too high. Another trap is choosing to "adjust the machine settings" or "interpret the rhythm" when the correct action is to fix the artifact and re-run the tracing. Do not place electrodes over bone or over a lotion-covered chest without cleaning. Never tell a patient the tracing is "normal."
Worked example
A tracing shows a wavy, drifting baseline. Rule of thumb: baseline wander means movement or respiration; coach the patient to lie still and breathe normally, then re-run. Muscle tremor looks fuzzy and spiky; warmth and reassurance help. 60-cycle interference looks like a thick, regular buzz; move electrical equipment away.
Rule of thumb
Fix the patient and the environment first; only then re-run the tracing.