How To Read An ECG

The ECG paper is mostly standardised

– Each large square on the paper represents 0.2 seconds
– Each small square represents 0.04 seconds
– 5 large squares therefore = 1 second
– 300 large squares = 1 minute
– To calculate heart rate – count large squares within an R-R interval & divide 300 by this number

P-waves

P-waves represent atrial depolarisation
There should be a P-wave preceding each QRS complex

QRS complex

The QRS-complex represents depolarisation of the ventricles
It is seen as 3 closely related waves on the ECG (Q,R & S wave);
The first downward deflection is the Q-wave
Any upward deflection is an R-wave
Downward deflections after an R-wave is called an S-wave
It should be between 0.06-0.10 seconds

T-wave

The T-wave represents ventricular re-polarisation
It is seen as a small wave after the QRS complex

To Understand More , Check This Photo And Watch This Short Youtube Video :