Presentation on theme: "Electrocardiography Prof. K. Sivapalan. 2013 ECG 2 Principle of Electrocardiogram. Trunk as volume conductor. Positively charged and negatively charged."— Presentation transcript:
2013 ECG 2 Principle of Electrocardiogram. Trunk as volume conductor. Positively charged and negatively charged areas create electrical field. The field changes during spread of impulse. Depolarization towards – upward deflection & away – downward deflection.
2013 ECG 3 Einthovens triangle. When the source of the electrical field is at the centre of an equilateral triangle, the sum of electrical potential at the three angles is zero. Since the heart is roughly at the centre of the triangle and the source moves, 5000 ohm resistance is added to the three leads to get zero potential.
2013 ECG 8 Electrocardiogram. Electrocardiogram is the record of the changes in the electrical field in the body produced by the electrical activity of the heart. It represents the sequence and strength of the electrical events in the heart.
2013 ECG 9 Recording ECG. Coronal plane: Limb leads [Bipolar leads]. Augmented limb leads.[unipolar] Transverse plane: Chest [Unipolar] leads V1 to V6 across the chest. Lead I Lead II Lead III aVR aVL aVF
2013 ECG 10 Typical Electrocardiogram. Paper speed- 25 mm/sec. Vertically, 1 mV = 10 mm. P wave – first wave. Q wave – first down. R wave – first up in QRS. S wave – down after R. T wave – after QRS. U wave – after T. PR interval – 0.18 sec. QRS duration – 0.08 sec.
2013 ECG 11 Information from ECG. Rate. Rhythm Pattern of spread of impulse and integrity of conducting system. Size [thickness] of myocardium. Electrolyte imbalance. Damage to myocardium.
2013 ECG 12 Examples of abnormal ECG. SA node block
2013 ECG 13 Examples of abnormal ECG. Normal. K + – 4 – 5.5 meq / L K+ – 7 meq / L. K+ – 8.5 meq / L K+ – 3.5 meq /L. K+ – 2.5 meq / L.