The electrical activity of the heart starts in the ‘internal pacemaker’, which is called the sinoatrial node. sinoatrial node. -Right atrium Normal rythm - Sinus rythm
Changes to the normal flow of electricity through the heart can be shown on an ECG and may indicate damaged heart muscle.
Each view of the heart is described as a ‘lead’. The word ‘lead’ does not refer to the electrodes.
The rhythm of the heart can be determined from only one view, i.e. one lead (this requires two electrodes). Leads: I, II, III, VL, VF and VR
Six electrodes are attached to the chest, recording leads V1 to V6 . Accurate placement of these electrodes is essential for comparing later ECGs
| R | Red | Right arm |
|---|---|---|
| G | Green | Left Leg |
| B | Black | Right Leg |
| Y | Yellow | Left Arm |
; the voltage calibration should be set so that 1 mV causes 1 cm of upwards deflection