ELECTROCARDIOGRAM (ECG) Cardiovascular System Physiology Lab Interpretation Dr.Mohammed Sharique Ahmed Quadri Asst. professor in physiology بسم الله الرحمن الرحيم

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

One way to diagnose an acute MI is to look for elevation of the ST segment.

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Elevation of the ST segment (greater than 1 small box) in 2 leads is consistent with a myocardial infarction.

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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

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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

Suggestive of Question NO: What is the most likely cause of changes in ST seg. & T wave of each diagram?

Ways the ECG can change include: Appearance of pathologic Q-waves T-waves peaked flattened inverted ST elevation & depression

 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