Basics of ECG Flashcards
Which part of the conduction cycle does the P wave represent on an ECG?
Atrial depolarisation
Which part of the conduction cycle does the QRS complex represent on an ECG?
Ventricular depolarisation
Which part of the conduction cycle does the PR interval represent on an ECG?
Delay through the AV node
Which part of the conduction cycle does the T wave represent on an ECG?
Ventricular depolarisation
A positive deflection on ECG indicates that electricity in travel in which direction with respect to that lead?
Towards the lead
A negative deflection on ECG indicates that electricity in travel in which direction with respect to that lead?
Away from the lead
What is the normal duration of the QRS complex on ECG?
<120ms
What is the normal duration of the PR interval on ECG?
120-200ms
Which interval on ECG requires correction for heart rate in order to interpret it properly?
QT interval
How long would a QT interval have to be on ECG for it to be considered prolonged?
> 450ms
Why is a prolonged QT interval on ECG significant?
It can predispose the cardiac rhythm to change into a ventricular tachycardia which may result in cardiac arrest
Which interval on ECG is used to determine heart rate?
RR interval
How can heart rate be calculated on ECG when there is a normal rhythm?
300 / number of large squares between R waves
How can heart rate be calculated on ECG when there is an abnormal rhythm?
Number of R waves present in rhythm strip x 6
What are the names of the three chest leads on ECG?
V1 V2 V3 V4 V5 V6
What are the names of the three limb leads on ECG?
I
II
III
What are the names of the three augmented leads on ECG?
aVL
aVF
aVR
Which ECG leads form a coronal view of the heart?
aVL aVF aVR I II III
Which ECG leads form a transverse view of the heart?
V1-6
Which ECG lead points towards 0 degrees on the cardiac axis?
I
Which ECG lead points towards +60 degrees on the cardiac axis?
II
Which ECG lead points towards +90 degrees on the cardiac axis?
aVF
Which ECG lead points towards +120 degrees on the cardiac axis?
III
Which ECG lead points towards -150 degrees on the cardiac axis?
aVR
Which ECG lead points towards -30 degrees on the cardiac axis?
aVL
Which ECG leads show an inferior view of the heart?
II, III, aVF
Which ECG leads show an anteroseptal view of the heart?
V1-4
Which ECG leads show an lateral view of the heart?
I
aVL
V5
V6
Where should the normal transition zone for R wave progression on ECG be?
leads. V3/4
Between which degrees should the normal cardiac axis lie?
-30 and +90 degrees
What are the signs of right axis deviation on ECG?
QRS complex is negative in lead I and positive in lead II
What pathology can cause right axis deviation?
Right ventricular hypertrophy
Left sided dysfunction
When might right axis deviation be normal?
In tall, thin individuals
What pathology can cause left axis deviation?
Left ventricular hypertrophy
Right sided dysfunction
What are the signs of left axis deviation on ECG?
QRS complex is positive in lead I and negative in lead II
In which ECG leads can it be normal to see a Q wave?
V5 V6 I aVL i.e. the lateral leads
