Basics of ECG Analysis
1. rate
2. rhythm
3. axis
Rate from ECG (estimated)
1) Find R close to bolder line
2) For each bold line passed to next R, count using pneumonic
3) Rate is between last 2 counts
S 3
1
6
t 0
0
0
1
5
7
a 0
0
5
0
5
r
0
t
1
Rate from ECG (estimated)
1) Find R close to bolder line
300
150
100
75
2) For each bold line passed to next R, count using pneumonic
3) Rate is between last 2 counts
Rate is estimated between 75 and 100 bpm
(normacardia)
s
300
150
100
ACTUAL HEART RATE CALCULATION
• 12 small squares between R's
• each small square = 1/25th sec
• 12/25th of a second for 1 beat
300 "one"
150 "two"
• 12/25 =.48 seconds per beat
• In 60 seconds there will be 60/.48 or
125 beats
100 "three"
Rate is between 100 & 150
Eyeball: halfway = 125
2
•25 squares between R's
•25/25th of a second
•25/25 =1.0 beat per second
300 150 100
75
60
•60/1.0 = 60 beats per minute
300 "one"
150 "two"
100 "three"
75
"four"
60
"five"
Rate is 60
300
•7 squares between R's
150
0
5
•7/25th of a second
•7/25 =.28 beats per second
•60/.28 = 214 beats per minute
300 "one"
150 "two"
Rate is between 150 and 300
Eyeball ?
225
3
5 beats
=
35
____mm
0
1
beats
214 Beats.min-1
1500mm
7500
2
3
4
5
1 second
How long does each beat take ? 60/214 = 0.28 sec
THIS IS THE TIME FOR THE CARDIAC CYCLE
Basics of ECG Analysis
1.
2.
3.
rate
rhythm
axis
4
Rhythm
• Is the source of the rhythm the SA NODE or an ectopic
pacemaker ? If the source is the SA NODE then the
rhythm is "sinus"
• Source of rhythm is SA NODE when
– there is a P before each QRS
– P is in the same direction as QRS
"P" is up
"QRS" is up
Rhythm is SINUS
P
Q
R
S
P
P
Q
R
S
Q
R
S
Rhythm
• Is the source of the rhythm the SA NODE or an ectopic
pacemaker ? If the source is the SA NODE then the
rhythm is "sinus"
• Source of rhythm is SA NODE when
– there is a P before each QRS
– P is in the same direction as QRS
"QRS" is up
No P Waves
Rhythm is not
SINUS
Q
R
S
Q
R
S
Q
R
S
Q
R
S
5
Basics of ECG Analysis
1. rate
2. rhythm
3. axis
Axis
• The mean electrical axis (MEA) in the
FRONTAL PLANE is the average of all the
instantaneous electrical vectors that are
generated as the ventricles “fire” during a normal
coordinated heart beat
• The MEA is a good indicator of the main
direction of electrical activity in the frontal plane.
• The direction and magnitude of the MEA an be
obtained from the limb leads (I, II, III,
avR,avL,aVF)
• The question in analysis “is the MEA NORMAL
or DEVIATED ?
6
Bipolar Standard Limb Leads
0o
Bipolar Standard Limb Leads
0o
60o
7
Bipolar Standard Limb Leads
0o
120o
Leads 1,2,3
0o
0o
0o
120o
120o
8
Augmented Unipolar Limb Leads
Putting all “limb leads on 1 “clock” shows how each changes
as the positive & negative electrodes’ placement moves around the limbs
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What would be recorded if
you switched Lead II
placement of + and - ?
2 steps to determining MEA
1. Find the lead where the QRS is most
evenly distributed above and below
“baseline” (isoelectric or biphasic lead)
2. Find the lead with the largest R wave
amplitude that is perpendicular to the
isoelectric lead.
10
NORMAL AXIS
DEVIATED AXIS less than -30o
greater than 120o
11