Electrocardiogram (ECG)

  • Electrocardiogram (ECG) is graphic record of the electric current produced by the excitation of the cardiac muscles. The instrument used to record the changes is an electrocardiograph.
  •  A normal electrocardiogram (ECG) is composed of P wave, a QRS wave (complex) and aT wave. The P wave is a small upward wave that indicates the depolarisation of the atria (atrial contraction). It is caused by the activation of SA node. 
  •  The QRS wave (complex) begins after a fraction of second of the P wave. It begins as of a standard ECG a small downward deflection (Q) and continues as large upright (R) and triangular wave ending as downward wave (S) at its base.
  • It represents ventricular depolarisation (ventricular contraction). The T wave is dome-shaped which indicates ventricular repolarisation (ventricular relaxation). The end of the T-ware marks the end of systole.
  •  By counting the number of QRS complexes in a given time period, we can determine the heart rate of an individual. 
  • Any deviation from the normal shape of ECG, indicates any disease or abnormality in a person.
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