What is an ECG?
• An ECG is a simple, noninvasive procedure.
Electrodes are placed on the skin of the chest
and limbs then connected in a specific order
to a machine that, when turned on, measures
electrical activit
...
What is an ECG?
• An ECG is a simple, noninvasive procedure.
Electrodes are placed on the skin of the chest
and limbs then connected in a specific order
to a machine that, when turned on, measures
electrical activity all over the heart. Output
usually appears on a long scroll of paper that
displays a printed graph of activity on a
computer screen.
12 Lead ECG
• The standard 12-lead
electrocardiogram is a
representation of the
heart's electrical activity
recorded from
electrodes on the body
surface.
• The spikes and dips in
the tracings are called
waves.
12-lead ECG
• 12-lead ECG
– 10 electrodes required to produce 12-lead ECG.
• Electrodes on all 4 limbs (RA, LL, LA, RL)
• Electrodes on precordium (V1–6)
– Monitors 12 leads (V1–6), (I, II, III) and (aVR, aVF, aVL)
– Allows interpretation of specific areas of the heart
• Inferior (II, III, aVF)
• Lateral (I, aVL, V5, V6)
• Anterior (V1–4)
3 & 5 Lead Cardiac Monitoring
• Monitor cardiac
functioning
• Controlled from central
monitor room at most
acute facilities
• Printable or electronic
strips are available and
place in chart at desired
times during 24 hour
period
3-Electrode System
• 3-electrode system
– Uses 3 electrodes (RA, LA and LL).
– Monitor displays the bipolar leads (I, II and
III)
– To get best results – Place electrodes on the
chest wall equidistant from the heart (rather
than the specific limbs)
5-electrode system
• 5-electrode system
– Uses 5 electrodes (RA, RL, LA, LL and Chest)
– Monitor displays the bipolar leads (I, II and
III)
– AND a single unipolar lead (depending on
position of the brown chest lead (positions
V1–6))
Understanding the ECG Grid
• ECG tracings are recorded on grid paper. The
horizontal axis of the EKG paper records time, with
black marks at the top indicating 3 second intervals.
• Each second is marked by 5 large grid blocks. Thus
each large block equals 0.2 second. The vertical axis
records EKG amplitude (voltage). Two large blocks
equal 1 millivolt (mV). Each small block equals 0.1
mV.
• Within the large blocks are 5 small blocks, each
representing 0.04 seconds.
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