ECGs Flashcards
What is the methodical approach to reading an ECG?
Name, age, DOB, ECG date Rate Rhythm Axis P wave PR interval QRS complex QT interval ST segment T wave J wave
How do you calculate the rate?
Either count the number of QRS complexes on a 10second strip, or do 300/number of big squares btwn QRS complexes
What should the ECG be set at?
25mm/s
10mm/mV
small square is 0.04
big square is 0.2
What are the different types of rhythm?
Regular
Regularly irregular
Irregularly irregular .
(AF/VF)
How do you determine the axis?
Look at leads 1 and 2/aVF
Normal axis = both leads 1 and 2/aVF are positive
Left deviation = lead 1 is positive and 2/aVF is negative
Right deviation = lead 1 is negative and 2/aVF is positive
Extreme deviation = both are negative
Leaving = Left
(the QRS in 1 and 2 are pointing away from each other)
Returning = Right
(the QRS in 1 and 2 are pointing towards each other)
What are some causes of left axis deviation?
Left anterior hemiblock Inferior MI VT from LV WPW LVH
What are some causes of right axis deviation?
Left posterior hemiblock Anterolateral MI PE WPW RVH
What are normal p waves?
Preceding each QRS complex
Positive in 2,3 and aVF
Negative in aVR
What are the abnormalities of p waves?
Absent: AF/AVRT
Sawtooth: Atrial Flutter
P mitrale (looks like an m): LAH
P pulmonale (peaked): RAH
Pseudo p-pulmonale: hyperkalaemia
Earlier than expected/abnormally shaped: ectopic p waves
How do you differentiate between AF and AVRT?
AF is irregularly irregular with a wavy baseline
ART is regular with narrow QRS
What can the PR interval tell us?
The normal range is 0.12-0.2 from start of P to start of QRS
A prolonged PR interval implies heart block.
1st degree = the PR interval is regular
2nd degree T1 = PR interval gets longer and longer then is reset “wenkebach”
2nd degree T2 = PR interval is normal but sometimes a p wave occurs without a QRS
3rd degree = completely random p waves and QRS complexes.
A short PR interval implies unusually fast AV conduction, e.g. WPW
What are the options if the HR is below 60 or +100?
<60 = sinus brady, sick sinus syndrome, 2/3 heart block, atrial/ventricular escape rhythm
> 100 = ST, SVT, AF, AVRT
Which directions are the QRS complexes supposed to go?
V1/2/3 = negative (3 a bit biphasic) V4/5/6 = positive aVR = negative
What is sinus arrhythmia?
When the HR = 75 during exp then 90 during insp
What is sick sinus syndrome?
When a p wave fails to appear but there is a random QRS complex
What is normal for a QRS complex?
<0.12s
3 small squares
What are the abnormalities with QRS complexes?
Ventricular ectopics = one random wide, shitty QRS every now and then
VT = zigzag QRS, can self terminate
Wide ‘M’ in V1 and ‘W’ in V4 QRS = RBBB
Wide ‘W’ in V1 and ‘M’ in V4 QRS = LBBB
BBB can be intermittent and can have ST elevation w/o MI
VF = random uncoordinated waves
VH = high amplitude waves
What is the normal QT interval, and what can a long QT mean?
Start of QRS to end of T. Usually 0.38-0.42
Prolonged QT can lead to VT and death
Short QT could be caused by hypercalcaemia and digoxin
What are atrial escape rhythm and ventricular escape rhythm?
Lack of p waves but normal QRS
If QRS is narrow = atrial escape rhythm
If QRS is broad then ventricular escape
What does the ST segment directly tell you about anatomically?
The coronary arteries
What can go wrong with ST segment?
ST depression: narrowed artery and ischaemia
ST elevation: occluded artery
How do you know where the MI was?
II, III, and aVF = inferior RCA
V1,2,3,4 = anterior LAD
I, V5,6 and aVL = posterior circumflex
How does an ECG change in accordance to the stages of an MI?
1st stage MI = smaller QRS with a huge T wave
2nd stage = wide Q wave
3rd stage = inverted T wave
What is a normal T wave?
Inverted in aVR, V1 and V2. Normal if inverted in isolation in lead III
