2. Electrocardiography (ECG)

3. Electrocardiogram  The tracing made by an electrocardiograph  Electrocardiograph an instrument for recording the changes of electrical potential occurring during the heartbeat used especially in diagnosing abnormalities of heart action

4. Sinoatrial Node (SA) the impulse generating tissue located in the right atrium of the heart Atrioventricular Node (AV) the tissue between the atria and the ventricles of the heart, conducts the normal electrical impulse from the atria to the ventricles Cardiac conduction system SA  AV  His bundle  Purkinje fibers

5. Electrocardiogram (ECG) (cont.)

6. ECG Waves and Intervals  P wave: the sequential activation (depolarization) of the right and left atria  QRS complex: right and left ventricular depolarization  ST-T wave: ventricular repolarization  U wave: probably represents "afterdepolarizations" in the ventricles  PR interval: time interval from onset of atrial depolarization (P wave) to onset of ventricular depolarization (QRS complex)  QRS duration: duration of ventricular muscle depolarization  QT interval: duration of ventricular depolarization and repolarization  RR interval: duration of ventricular cardiac cycle (an indicator of ventricular rate)  PP interval: duration of atrial cycle (an indicator of atrial rate)

7. ECG Signal Characteristics  Signal is generated in the heart  Amplitude range: -5 mV to +5 mV (usually the packed up signal on the body surface is 1 mV)  Frequency range: 0.05 to 1500 Hz  Acquisition by surface electrodes

8. Lead configurations for ECG Acquisition 1.Bipolar limb leads (Einthoven) 2.Unipolar limb leads or Augmented limb leads (Goldberg) 3.Unipolar chest leads (Wilson)

9. Bipolar limb leads (Einthoven) Lead ILead IILead III

10. Signal shape of Bipolar limb leads (Einthoven) Lead I Lead II Lead III

11. Unipolar limb leads or Augmented limb leads (Goldberg) Lead aVRLead aVLLead aVF

12. Signal shape of Unipolar limb leads Lead aVR Lead aVL Lead aVF

13. Signal processing of ECG

14. Signal processing of ECG (cont.)  Block diagram of ECG measurement circuit Limb lead electrodes Band reject filter 60 Hz Lead loop High pass filter 0.1 Hz Pre-amplifier × 100 Low pass filter 100 Hz Isolator Amplifier × 10 Right arm Left arm Right leg Left leg ECG

15. Lead loop Pre- amplifier Isolator High pass filter Low pass filter Band reject filter Amplifier ECG Lead Switch Right arm Left arm Right leg Left leg Signal processing of ECG (cont.)