‫بسم هللا الرحمن الرحيم‬
Cardiovascular System
Physiology Lab
ELECTROCARDIOGRAM (ECG)
Interpretation
Dr.Mohammed Sharique Ahmed Quadri
Asst. professor in physiology
ANALYZING INDIVIDUAL WAVES & SEGMENTS

P wave : upright except in avR
Normal duration: 0.08 to 0.11 sec
do you see p waves ?
are all p waves same ?
does all QRS complexes have p waves ?

P-R interval : Normal range 0.12 – 0.20 sec
Is the PR interval constant ?
If prolong indicates various blocks
2
ANALYZING INDIVIDUAL WAVES & SEGMENTS

QRS complexes:
 Are the p waves & QRS complexes are associates with each
other
 Are the QRS complexes narrow or wide

ST Segment :
 Normal : Isoelectric
 Elevation : in acute MI
 Depression : in ischemia

T wave:
 Tall T wave : ischemia, hyperkalemia
 Inverted : young children ,deep inspiration, bundle branch
block, ischemia,hypokalemia
3
ANALYZING INDIVIDUAL WAVES & SEGMENTS

QT INTERVAL:
 0.4 to 0.43 seconds depending upon heart rate.

At high heart rates, ventricular action potentials
shorten in duration, which decreases the Q-T
interval.

. prolonged in acute MI ,hypocalcaemia
4
Variation in ST segment
ST ELEVATION
One way to
diagnose an
acute MI is to
look for
elevation of the
ST segment.
ST ELEVATION SUGGESTIVE OF MI
7
ST ELEVATION (CONT)
Elevation of the ST
segment (greater
than 1 small box)
in 2 leads is
consistent with a
myocardial
infarction.
9
PUTTING IT ALL TOGETHER
Do you think this person is having a myocardial
infarction. If so, where?
Yes, this person is having an acute anterior wall
myocardial infarction.
Now, where do you think this person is having
a myocardial infarction?
Inferior wall MI
How about now?
Anterior & lateral wall MI
NORMAL
HYPERKALEMIA
HYPOKALEMIA
13
14
INTERPRETE THE ECG ?
HYPERKALEMIA
Observe Tall T - wave
15
REPORTING OF ECG

This ecg shows
Sinus rhythm
 Heart rate of 75/ min
 Normal QRS axis
 Normal PR interval 0.12 sec
 Normal QRS duration 0.8 sec
 ST segment isoelectric in all leads
 T wave normal & upright in all wave except in aVR

16
REFERENCES
Text book of medical physiology by GUYTON &
HALL 11 th edition
 Text book physiology by GANONG
 The ECG made Easy by John R.Hampton sixth
edition
 The guide to EKGinterpretation by JohnA.Brose,
D.O,John C.Auseon

17
Prof. Magdy El-Barbary
Prof. Magdy El-Barbary
Question NO:
Suggestive of
What is the most likely cause of changes in ST seg. & T wave of each
diagram?
ECG CHANGES
Ways the ECG can change include:
ST elevation &
depression
T-waves
peaked
Appearance
of pathologic
Q-waves
flattened
inverted
REFERENCES
Text book of medical physiology by GUYTON &
HALL 11 th edition
 Text book physiology by GANONG
 The ECG made Easy by John R.Hampton sixth
edition
 The guide to EKGinterpretation by JohnA.Brose,
D.O,John C.Auseon
