Interpretation Made Easy
LEAD PLACEMENTLIMB LEADS MUST BE PLACED ON THE
LIMBSUses both positive and negative electrodesCurrent towards positive, view from negative
Precordial Leads
Acquisition & Transmission
Acquisition & TransmissionSkin Preparation
Helps obtain a strong signalSkin oils reduce adhesion of electrode
and hinder penetration of electrode gelDead, dried skin cells do not conduct
well
Acquisition & Transmission
Rubbing skin with a
gauzepad can
reduce skin oil
and remove some of
dead skin cells
Acquisition & TransmissionOther causes of artifact
Patient movement
Cable movement
Vehicle movement
Electromagnetic Interference (EMI)
Acquisition & TransmissionPatient Movement
Make patient as comfortable as possible Supine preferred
Look for subtle movement toe tapping, shivering
Look for muscle tension hand grasping rail, head raised to
“watch”
Acquisition & TransmissionCable Movement
Enough “slack” in cables to avoid tugging on the electrodes
Many cables have clip that can attach to patient’s clothes or bed sheet
Acquisition & TransmissionElectromagnetic Interference (EMI)
Can interfere with electronic equipment60 cycle interference is a type of EMILook for nearby cell phones, radios or
electrical devicesNo contact between cables & power
cordsTurn off or move away from AC devicesUse shielded cables; inspect for cracks
Limb Lead PlacementTraditional Placement
Acceptable Placement
Avoid placing on the trunk!!!
Chest Lead PlacementV1: fourth intercostal space
to right of sternumV2: fourth intercostal space
to left of sternumV3: directly between leads
V2 and V4V4: fifth intercostal space at
left midclavicular lineV5: level with V4 at left
anterior axillary lineV6: level with V5 at left
midaxillary line
Acquisition & TransmissionThings to look for
Little or no artifactSteady baseline
Acquisition & Transmission
12-Lead ValidationLead I – Global Negativity?
P, QRS and T Wave inverted?R Wave Progression?
R Wave size increases in V leadsTransition Zone?
R Wave should be predominately positive in V3 and V4
12-Lead ValidationLimb leadsP wave, QRS, and
T wave upside down in Lead I
Global negativityUpper limb leads
switched
12-Lead ValidationR wave
progressionR waves progress
in size from V1 to V4
If poor progression, check lead placement on electrodes
normal poor