The Electrocardiogram

The EKG/ECG

• Diagnostic procedure that graphically records the conduction, magnitude, and duration of electrical current generated by the heart

• an instrument that detects and records electrical impulses produced by action of heart with each beat

EKG uses:

• identify

  • rhythm disturbances

  • conduction abnormalities

  • electrolyte imbalances

• info on heart size

  • chamber dimension

  • wall thickness

• info on heart position

  • will change s/p surgery and w/ age

EKG uses:

• Diagnosis and/or monitoring of:

  • MI

  • ischemia

• evaluate pacemaker function

  • a device generating electrical impulses to stimulate contraction of heart muscle at a certain rate

  • worn externally or implanted in the body

    • wire will be seen in the RA and RV as thin, linear, hyperechoic structure

Limitations of EKG / ECG:

• records past and present function

  • cannot predict future problems

• must be correlated w/ patients

  • chemical assessment / lab values

  • drug therapy

• healthy heart can show changes

  • can have normal variants

  • hook up must be standardized for accurate comparison

Limitations of EKG / ECG:

• only measures electrical activity

  • this can help detect damage to a partion of heart wall

• cannot detect ejection fraction or actual function of heart

  • Echocardiography can!

• displays approx. 20 seconds of activity

  • a major limitation

3 Lead EKG AKA:

• single lead

• rhythm lead

3 Lead EKG

• continuous monitoring

• looks at only one view of the heart

  • used w/ an Echocardiogram for timing

  • used for a quick look at electrical stimulation

3 electrodes used with 3 Lead EKG:

• positive - black

  • placed on left side of chest

• negative - white

  • placed on right side of chest

• ground - red

  • minimizes electrical activity from other sources

    • placed on torso

12 Lead EKG

• the real diagnostic EKG test

• records 12 views of the heart

  • uses a combo of leads

• only 10 electrodes / leads placed on body

Reasons for performing 12 Lead EKG:

• resting electronic information rendered

• aid in ID of conduction disorders

• monitor MI recovery

• evaluate pacemaker function

• evaluate drug therapy

12 Lead EKG procedure:

• access to chest, arms, and legs

• pt supine

  • palms up

• to reduce artifact:

  • Remove watch

  • NO talking, movement, tenseness

Machine Filter

• must be “on”

• reduces artifact

  • tremors

  • movement

  • loose electrodes

  • poorly placed electrodes

  • 60 cycle interference

    • an electric artifact

    • interference from room or same electric outlet

• artifact may be present as “shaggy”, thick line

Electrode Placement

• clean, dry, lotion-free skin

• shave men w/ hairy chest

• sandpaper dry, flaky skin

• electrodes have gel/medium on them

  • can add more gel for better transmission

• leads placed so they form an arch around the heart

  • ground leads are placed on limbs

12 Lead EKG placement:

• V2: 4 intercostal spaces down from Lt clavicle

• V4: directly below pt’s nipple

• V6: inferior to Lt armpit on torso

• V1: directly across sternum from V2

• V3: in between V2 and V4

• V5: in between V4 and V6

• RA: Rt arm, deltoid m

• LA: Lt arm, deltoid m

• RL: Rt leg, calf

• LL: Lt leg, calf

EKG Paper

• graph paper

  • x-axis: time

  • y-axis: voltage/amplitude/height of waveform

• Calibrate Machine!

X-axis of EKG paper: time

• run at constant speed

• small square = 0.04 of a second

• large square = 0.20 of a second

• 5 large squares = 1 second

Y-axis of EKG paper: voltage/amplitude/height of waveform

• small square = 1 mm high = 0.1 millivolt

• large square = 5 mm high = 0.5 millivolt