EKG Equipment, Lead Placement, and Artifact Recognition
Accurate lead placement is the foundation of a valid tracing. A misplaced lead produces a pattern that mimics pathology-a classic exam trap.
Standard 12-lead placement
Limb leads: RA right arm, LA left arm, LL left leg, RL right leg (ground). Chest leads: V1 fourth intercostal space, right sternal border; V2 fourth intercostal space, left sternal border; V3 between V2 and V4; V4 fifth intercostal space, midclavicular line; V5 anterior axillary line at V4 level; V6 midaxillary line at V4 level.
Artifact types and fixes
- Somatic tremor (muscle): fuzzy baseline from shivering or movement; warm the patient, relax arms, reassure.
- Baseline wander: slow undulation from respiration or loose electrodes; reapply, secure cables.
- 60-cycle interference: thick, dark, uniform tracing from electrical sources; check grounding, move away from equipment, verify electrode contact.
- Loose/disconnected electrode: flat line or erratic spikes; reattach.
- Wrong limb lead reversal: RA/LA swap flips lead I; examine P waves if suspicious.
Traps
Questions show a fuzzy baseline and ask the cause (muscle tremor) or a wandering baseline attributed to poor contact. Do not confuse 60-cycle interference (uniform thickness) with somatic tremor (irregular fuzz). Also remember electrodes go on clean, dry skin, hair may be clipped (not shaved if avoidable), and gel electrodes should not be reused.
Rule of thumb: Artifact is not rhythm. If the underlying rhythm is visible through the noise, treat the noise; if not, fix the connection before interpreting.