A first look at the ECG Flashcards
In which direction is an electrical signal travelling if the ECG blip is positive going?
The signal is travelling towards the electrode
In which direction is an electrical signal travelling if the ECG blip is negative going?
The signal is travelling away from the electrode
Which leads are the standard limb leads?
I, II & III
Which leads are the augmented limb leads?
aVR, aVL & aVF
Which leads are the chest leads?
V1-V6
Which plane do the standard limb leads (I-III) look at the heart in?
The frontal plane
Which limbs are connected by standard limb lead I?
Left and right arm
Which limbs are connected by standard limb lead II?
Left and right arm
Which limbs are connected by standard limb lead III?
Left leg and right arm
What does each aspect of the QRS represent?
Q= The small negative going blip at the start of the QRS is the inter ventricular septum depolarising from left to right
R= depolarisation of the ventricle towards the electrode (positive going blip)
S= The upper part of the interventricular septum depolarises in a cranial direction (away from the the electrode)
In which direction does the heart repolarise?
From the top towards the apex (same direction as depolarisation)
What causes a change in the size of the QRS complex on the ECG tracing?
Hyper or hypotrophy will cause the anatomy of the heart, and therefore the orientation of electrical signals, to shift slightly
As the position of the interventricular septum shifts, the direction that the electrical signal travels changes slightly and it may be detected more or less on certain leads.
What is a normal PR interval?
0.12-0.2s
What is happening in the heart during the PR interval?
The electrical signal is bing transmitted through the AV node
What is the usual time associated with the QRS complex??
0.8s
What is a normal QT interval at a resting heart rate of around 60?
0.42 seconds
Why is it not possible to see atrial repolarisation on an ECG?
Atrial repolarisation is lost within the QRS complex because there are far more ventricular cells than atrial cells so the electric signal is much stronger coming from the ventricles
In which augmented limb lead is depolarisation picked up best?
aVF
Why is the ECG trace inverted in aVR?
Because the depolarisation is moving away from this lead
Why is the trace very small in aVL?
because this lead is the furthest from the direction of depolarisation
In which plane do the chest leads look at the heart?
Horizontal
Describe what is meant by “progression” in the chest leads
Progression is when the ECG trace flips from a negative-going blip to a positive-going blip between the chest leads (Progression usually occurs somewhere between leads V2/V3/V4)
Whic chest leads should always show;
A) A negative-going blip
B) A positive-going blip
A) V1
B) V6
At what speed should ECG paper run at?
25mm/s
How can you tell if the ECG paper is running at the correct speed
If the paper is running at the correct speed, the calibrating pulse should take up one large box
How can you work out heart rate from a rhythm strip?
Count how many QRD complexes there are in 30 large boxes then multiply it by 10
What is classed as tachycardia?
A heart rate >100BPM
What is classed as bradycardia?
A heart rate <60BPM
What is a normal heart rate?
60-100BPM
What is the acronym used to read an ECG.
ARIBAR
A= any electrical activity? R= Rate I= Irregular or regular rhythm B= Broad QRS complexes A=Any P-waves? R= Relationship between the P-wave and the QRS complex?
