Tuesday, June 17, 2008

Ecg paper


  • A typical electrocardiograph runs at a paper speed of 25 mm/s
  • Each small block of ECG paper is 1 mm². At a paper speed of 25 mm/s, one small block of ECG paper translates into 0.04 s (or 40 ms).
  • notice that the line b/w every five boxes are heavier,so that each 5mm unit horizontally corresponds to 0.2 sec.

  • vertically,ecg graph measures voltages or amplitudes of waves.the exact voltages can be measured because the electrocardiograph is standardised (calibrated) so that a 1mV signal produces a deflection of 10mm amplitude (1mV=10mm).
  • suppose in patients with electronic pacemakers that produces very large spikes or high QRS voltages caused by hypertrophy,it is advisable to take ecg at half standardization (1mV=5mm) to get the entire tracing on paper.
  • if ecg complexes are very small ,it is advisable to take ecg at double standardization (1mV=20mm) to study more clearly.

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