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ELECTROCARDIOGRAM (ECG) Cardiovascular System Physiology Lab Interpretation Dr.Mohammed Sharique Ahmed Quadri Asst. professor in physiology Slide 2 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 Slide 3 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 Slide 4 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 Slide 5 Variation in ST segment Slide 6 One way to diagnose an acute MI is to look for elevation of the ST segment. Slide 7 7 Slide 8 Elevation of the ST segment (greater than 1 small box) in 2 leads is consistent with a myocardial infarction. Slide 9 9 Slide 10 Do you think this person is having a myocardial infarction. If so, where? Yes, this person is having an acute anterior wall myocardial infarction. Slide 11 Now, where do you think this person is having a myocardial infarction? Inferior wall MI Slide 12 How about now? Anterior & lateral wall MI Slide 13 NORMAL HYPERKALEMIA HYPOKALEMIA 13 Slide 14 14 Slide 15 INTERPRETE THE ECG ? HYPERKALEMIA Observe Tall T - wave 15 Slide 16 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 Slide 17 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 Slide 18 Prof. Magdy El-Barbary Slide 19 Slide 20 Suggestive of Question NO: What is the most likely cause of changes in ST seg. & T wave of each diagram? Slide 21 Ways the ECG can change include: Appearance of pathologic Q-waves T-waves peaked flattened inverted ST elevation & depression Slide 22 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