ECG's Flashcards
What is an ECG?
A recording of the electrical activity of the heart.
Where does the electrical activity travel in the heart?
SA node (RA) to Bachmans bundle (LA) and AV node. Then to bundle of His and down bundle branches to Purkinje fibres through ventricles.
What is happening in depolarisation?
When sodium floods in a potassium floods out and the electrical wave moves.
Repolarisation is what?
When the sodium and potasium resore to normal.
Contraction is depolarisation or repolarisation?
depolarisation.
Relaxing of the cardiac muscles is depolarisation or repolarisation?
repolarisation.
Where are the lead placements of a 3 lead ECG?
red-right arm, yellow- left arm, black- right leg, green- left leg.
How many leads does a 3 lead ECG have?
4
Which way are the ‘pictures’ taken?
Right arm to left arm (lead 1), Right arm to left leg (lead 2). Left arm to left leg (lead 3).
When is a positive deflection?
when electricity is towards a positive.
When is a negative deflection?
when electricity is away from a positive
what is the isoelectic line
the invisible line of an ecg that everything returns to
which lead is the most positive and why?
lead 2 because overall wave of electricity is right atria to left venticle.
how fast does ecg paper travel
25mm per second
the tiny square on an ecg is how long?
0.04 seconds
5 tiny squares on an ecg are how long
0.2 seconds
time runs which way on ecg paper
across
What is a P wave
depolerisation of atria (positive)
How long should a P wave be?
0.08-0.12 seconds (2-3 squares)
What is the PR interval?
time between start of P wave and start of QRT complex
How long should PR be?
0.12-0.2 seconds (3-5 squares)
What hapens in the heart at PR
AV node holds electricity
QRS complex represents what?
ventricular depolarisation
How long should a QRS interval be?
0.04-0.12 seconds (1-3 squares)