Practical ECG methods Flashcards
What is an ECG electrode?
Tabs with a sticky back that are attached to cables/wires and stuck to the skin
What is an ECG lead?
The graph
What does the steepness of the ECG denote?
The velocity of the action potential
What does a downward deflection mean?
The action potential is moving towards the negative electrode
What does the isoelectric line represent?
No net change in voltage/change in direction
What does a sharp turn represent?
Rapid change in direction
What do upward deflections represent?
Action potential towards the positive electrode
How many electrodes are attached to the body for an ECG?
10
What does the P wave represent?
Atrial depolarisation and it is an upward spike as the positive electrode is situated near the apex of the heart
What does the isoelectric line after the P wave represent?
Depolarisation of AVN
What does the Q wave represent and why is it downwards?
Left bundle branch allows electrical impulse to go to the ventricles (septal depolarisation) towards the negative electrode. Very fast because very good conductor
What does the end of the isoelectric line before the Q wave represent?
Bundle of His conduction
What does the R wave represent?
Ventricular depolarisation via Purkinje fibres which is very conductive so fast – upwards peak as towards the positive electrode
What does the S wave represent?
Late ventricular depolarisation but the spike is downwards as up the ventricle side via Purkinje fibers
What does the isoelectric line after the S wave represent?
Fully depolarised ventricles
What does the T wave represent?
Ventricular repolarisation occurs towards the negative electrode so upwards peak
Where does lead 1 (ECG) go on the body?
Right arm to left arm
Where does lead 2 (ECG) go on the body?
Right arm to left leg
Where does lead 3 (ECG) go on the body?
Left arm to left leg
Where does the v1 lead go?
Right sternal border in the 4th intercostal space
Where does the v2 lead go?
Left sternal border in the 4th intercostal space
Where does the v3 lead go?
Halfway between the v2 and v4
Where does the v4 lead go?
Mid clavicular line in the 5th intercostal space
Where does the v5 lead go?
Anterior axillary line at the level of v4
Where does the v6 lead go?
Mid axillary line at the level of v4
To calculate the QRS axis how many leads do you need and what angle must they be at?
2 leads are needed and 90 degrees apart (e.g. lead 2 and lead aVL
Which leads are bipolar and which are unipolar?
leads 1-3 are bipolar and rest are unipolar
Which leads are in the coronal plane and which are in the horizontal plane?
Leads 1,2,3 and aVR, aVL, aVF are coronal and all chest leads are horizontal
