ECG Flashcards
To understand, perform and interpret ECGs
What causes a downward deflection?
Movement of the electricity away from the electrode
What causes an upwards deflection?
Movement of the electricity towards the electrode
What is the heart doing during the P wave?
Depolarisation spreading through the atria (atrial contraction)
What happens in the heart between the P wave and QRS complex?
The impulse passes through the AV node
What is the heart doing in the QRS complex?
Ventricle depolarisation/contraction, and atrial repolarisation
What is the heart doing in the T wave?
Repolarisation of ventricles
What is PEA?
Pulseless electrical activity - the appearance of normal-looking complexes on the ECG that should produce a pulse, but do not.
Can suggest PE, tamponade, tension pneumothorax, body salt disturbance, haemorrhage, lack of o2 due to hypothermia.
Why is it called a 12-lead ECG?
There are 10 physical leads - 4 limb leads, 6 chest leads. one of which is earth, and the other 9 create a plane from their interaction through which 3 more leads can be ‘created’.
What should the settings of the ECG machine be?
Paper speed: 25mm/s, 10mm/mV
Filter:150Hz
Where do you place the 4 limb leads?
Anterior forearms and medial mid-tibia. R = Right arm L = Left arm F = Left foot N = Right foot
Where do the chest leads go?
V1: 4ICS R V2: 4ICS L V4: 5ICS L Mid Cl V3: Between V2/4 V6: In line with V4 Mid Ax V5: Between V4/6
Why is a QRS complex both up and down?
The electrode is at an angle to the current, so first the current moves toward it, then away from it.
How long is each ‘small square’ and ‘big square’?
Small = 1mm = 0.04s Big = 5mm = 0.2s
Describe how the limb leads look at the heart.
aVR = RA from right arm aVL = laterally from left arm aVF = inferiorly I = laterally from a combination of aVL and aVF II = inferiorly from a combination of aVF and aVR III = inferiorly from a combination of aVF and aVL
Describe how the chest leads look at the heart.
ALL HORIZONTAL PLANE
V1/2 = Septum
V3/4 = anterior wall
V5/6 = lateral plane
How long should the P-R interval be?
0.12-0.2 seconds
How long should the QRS complex be?
0.12s max (3 small squares)
More than this defined as broad.
In which leads can you see QRS complexes?
V4-6
Which lead should you use to interpret the ECG?
II
How do you calculate the HR?
300/no of big squares between R waves
What does a broad QRS indicate?
Conduction problem
Impulse originates in ventricles e.g ventricular tachy
What does absence of P waves & irregular QRS indicate?
AF
What does absence of P waves & narrow QRS & tachycardia indicate?
supraventricular tachycardia
What does a ‘tooth like’ p wave suggest?
Atrial flutter - SA node firing at 300 beats per minute and AV node only lets through one every other 2/3/4 giving a reliable pulse of 150, 100 or 75bpm
What does the a longer than 0.2s PR interval indicate?
The AV node is holding onto the impulse for slightly too long = 1st degree heart block
What are the two types of 2nd degree heart block?
Mobitz I & II - Mobitz I can also be known as WInky Back
What is Winky Back?
Mobitz I, 2nd degree heart block, defined by progressively lengthening PR intervals followed by the dropping of a QRS complex before resetting itself and starting again.
What is Mobitz II?
2nd degree heart block characterised by the dropping of a QRS complex completely with otherwise normal intervals.
What is 3rd degree heart block?
Also known as complete or AV block. A total disassociation between P waves and QRS complexes. The AV node is on strike, but because the ventricles are waiting for an impulse, they assume that the communication lines are down and randomly contract as an emergency plan to keep things going.
What do you do if you see 3rd degree heart block?
GET HELP IMMEDIATELY
