ECGs

• Electrocardiography

  Used to monitor and investigate the electrical activity of the heart
• Electrocardiography

  1. Electrodes placed on skin surface (detect changes in electrical signals)

  2. Electrodes produce an electrocardiogram (ECG)
• P wave


  Caused by the depolarisation of the atria, which results in atrial contraction (systole)
• QRS complex


  • Caused by the depolarisation of the ventricles, which results in ventricular contraction (systole)
  • Largest wave because the ventricles have the largest muscle mass
• T wave


  Caused by the repolarisation of the ventricles, which results in ventricular relaxation (diastole)
• U wave


  Scientists are still uncertain of the cause, some think it is caused by the repolarisation of the Purkyne fibres
• The bigger the wave, the greater the electrical activity passing through the heart, which results in a stronger contraction
• Depolarization


  The process by which electrical impulses cause the heart muscle cells to contract and pump blood.
• S wave

  Represents the final depolarization of the ventricular walls.
• R wave


  Represents the main depolarization of the ventricles.
• Q wave


  Represents the initial depolarization of the ventricular septum (the wall that separates the left and right ventricles).
• QRS complex


  A part of the ECG waveform that represents the depolarization of the ventricles, which results in ventricular contraction (systole). The largest wave in the ECG due to the ventricles having the largest muscle mass.