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CARDIOVASCULAR SYSTEM ELECTROCARDIOGRAM (E.C.G.) LECTURE - 5 DR. ZAHOOR ALI SHAIKH 2

It is recording of Electrical activity of the Heart by putting Electrodes on the surface of the body. 3

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ECG  What is Lead? ECG recorded on the paper after putting the electrode.  What is Electrode? It is a metallic plate which conducts electricity. 5

6 ECG Machine Electrode

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Bipolar Limb leads Unipolar Limb Leads Unipolar chest leads 8

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ECG In bipolar lead, we record potential difference between two active electrodes. In Unipolar lead, we record potential difference between active electrode and other electrode at zero potential. If current is flowing towards the recording electrode, we get upward deflection. If current is flowing away from the recording electrode, we get downward deflection. 11

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16 Heart Rate Calculation = 1500 ÷ No. of small squares between R-R waves Or = 300 ÷ No. of big squares between R-R waves

The Waves & Intervals 17

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19 P wave  Atrial Depolarization During  0.12 sec Voltage (Height) 1-3mm QRS Complex  Ventricular Depolarization Time  0.08 – 0.1 sec Voltage  10mm (1mV) T wave  Ventricular Repolarization Height 2-3mm U wave  Repolarization of Papillary Muscles PR interval  Conduction time from SA node to Ventricular muscle through AV node. It measures the time from beginning of P wave to beginning of Q wave. Time 0.12 – 0.2 sec. QT Interval  Ventricular Depolarization or Repolarization Time 0.35 – 0.43 sec

REMEMBER IMPORTANT NORMAL VALUES 20 P wave sec QRS sec PR Interval sec QT Interval sec

ELECTRICAL AXIS 21

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1 st Degree Heart Block ST Elevation – Myocardial Infarction 27

WHAT YOU SHOULD KNOW FROM THIS LECTURE? 1.P wave ---- Atrial depolarization. 2.QRS complex ---- Ventricular depolarization.. 3.T wave ---- Ventricular Repolarization. 4.P – R interval ---- conduction time from S-A node to ventricular muscle through A-V node time =0.12 – 0.2sec. 5.↑PR interval more than 0.2 sec.---- Ist degree heart block. 6.Q – T interval ---- Ventricular depolarization + ventricular repolarization time =0.35 – 0.43sec. 28

7.↑QT interval ---- hypocalcemia. 8.U wave ---- repolarization of papillary muscle. 9.Prominent U wave ---- hypokalemia. 10.Prominent T wave ---- hyperkalemia. 11.Heart rate calculation 12.Sinus tachycardia 13.Sinus bradycardia 14.Sinus arrhythmia (↑ heart rate during inspiration) 15.Cardiac axis by looking at ECG lead I & III By plotting 29

16.Normal cardiac axis 0 o to + 90 o (-30 o to o ) 17.You should know about Left axis deviation & right axis deviation. 30

THANK YOU 31