Electrocardiograms

• Electrocardiograms (ECGs)


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


  1. Electrodes placed on skin

  2. Electrodes produce an electrocardiogram (ECG)
• ECG


  • Shows distinctive electrical waves produced by the activity of the heart
  • A healthy heart produces a distinctive shape
• 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
• Tachycardia


  When the heart beats too fast, resting heart rate over 100 bpm
• Bradycardia


  • When the heart beats too slow, resting heart rate below 60 bpm
  • Common in fit individuals and athletes, usually not dangerous
• Ectopic heartbeat


  • Caused by an early heartbeat followed by a pause
  • Common in the population and usually requires no treatment unless very severe
• Fibrillation


  • An irregular heartbeat that disrupts the rhythm of the heart
  • Severe cases can be very dangerous, even fatal
• Tachycardia


  • Peaks too close together, resting heart rate 130 bpm
• Bradycardia


  • Peaks too far apart, resting heart rate 60 bpm
• Ectopic heartbeat


  • Heart beat comes too early and is followed by a pause
• Fibrillation


  • Heartbeat is irregular so the rhythm is lost