ECGs Flashcards
How do you calculate HR on ECG?
300/no. of large squares between R-intervals
If pulse irregular: total R waves on ECG X 6
What HR counts as sinus bradycardia?
<60bpm
What HR counts as sinus tachycardia?
> 100bpm
How do you check the regularity of HR?
mark 4 R peaks on a piece of paper, move along trace to confirm
How do you check that an ECG is in sinus rhythm?
look for a P before every QRS complex
What are the two common features of AF on an ECG?
no clear P waves
Irregular QRS complex
Which arrhythmia presents with a ‘sawtooth’ baseline?
atrial flutter
What arrhythmias may present with broad-complex tachycardia with no p waves?
VF
VT
sometimes SVT with BBB/WPW
What are key features of SVT?
narrow complex tachycardia
abnormal or no P waves
How can you confirm that an ECG does not have any axis deviation?
QRS complexes in lead I and II are predominantly positive
How can you identify left-axis deviation?
R waves point away from each other in leads I and II
QRS predominantly +ve in lead I and negative in lead II
What are some common causes of L-axis deviation?
LV hypertrophy/strain L anterior hemiblock Inferior MI WPW VT
(anything where more electricity is going towards left)
How can you identify right-axis deviation?
R waves point towards each other in leads I and II
QRS predominantly -ve in lead I and positive in lead II
What are some common causes of R-axis deviation?
tall, thin body type RV hypertrophy/strain eg. PE L posterior semi-block lateral MI WPW
How tall should a P-wave be?
<=2 small squares
What might cause a raised p wave?
right atrial hypertrophy (caused by pulmonary hypertension or tricuspid stenosis)
How long should the PR interval be?
3-5 small squares
What can cause an increase in PR interval?
AV block ‘heart block’
How can you identify 1st degree AV block?
PR>5 small squares and regular
What are the different types of 2nd degree AV block?
Mobitz type 1 (Wenkebach)
Moritz type 2 - 2nd degree AV block with 2:1/3:1/4:1 block
What are the features of Mobitz type 1 heart block (Wenkebach)?
PR progressively elongates until there is failure of conduction of an arterial beat
(then cycle repeats)
What are the features of Mobitz type 2?
constant normal PR interval
Occasional dropped ventricular beats
(constant ratios: 2:1/3:1/4:1)
What is third degree heart block commonly known as?
complete heart block
What are the features of 3rd degree heart block?
complete dissociation between p waves and QRS complexes
What are some causes of 1st and second degree AV block?
increased vagal tone/athletes coronary artery disease myocarditis acute rheumatic carditis digoxin toxicity electrolyte disturbances
What are some causes of 3rd degree heart block?
fibrosis around bundle of His caused by ischaemia, congenital, idiopathic, aortic stenosis or trauma) or block of both bundle branches
How should R waves progress?
QRS complexes should progress from mostly negative in V1, to completely positive in V6
How big should a QRS segment be?
<3 small squares
What can cause an increase in QRS complex length?
bundle branch block
How can you identify RBBB?
QRS in V1: M pattern
QRS in V6: W pattern
How can you identify LBBB?
QRS in V1: W pattern
QRS in V2: M pattern
What can cause RBBB?
normal variant
atrial septal defect
PE
What can cause LBBB?
ischaemic disease acute MI cardiomyopathy hypertension aortic stenosis
Where should you look to assess QRS complexes?
Chest leads: for R wave progression
Rhythm strip: R wave length
Where should you look to assess QRS height?
V1 and V5/6
How high should a QRS be?
<4 squares
What can cause a R wave > 5 big squares (in V5/6)?
LVH
normal (physically fit pts)
What can cause a dominant wave in V1?
RVH (if there are other signs too eg. T wave inversion in R chest
Where should you check for Q waves?
all leads
What are Q waves a sign of?
Previous MI (but small Q waves can be normal in ! aVL and V6)
Full-thickness MI
In which leads should you check the ST segment?
All leads
What counts as ST elevation?
increase by >=1 small square
What can ST elevation be a sign of?
Infarction
Pericarditis or tamponade if in every lead
What counts as ST depression?
reduction by >=1 small square
What can ST depression be a sign of?
ischaemia
posterior infarction ‘reciprocal change’
What are the different types of ST changes (apart from elevation and depression)? What do they suggest?
Saddled: pericarditis/tamponade
Upward sloping: normal variant
Downward sloping (reverse tick): digoxin toxicity
In which leads should you check the T wave?
All leads
In which leads is T wave inversion normal? Why?
III, aVR and V1 (also V2-3 in black people)
Due to the angle from which they look at the heart
What can cause T-wave inversion (in leads where this would not be considered normal)?
ischaemia/post=MI
R/L VH
Bundle branch block
digoxin treatment
What can cause tall-tented T waves?
Hyperkalaemia
What can cause flat T waves?
Hypokalaemia
What should the QT interval be?
<450ms (ECG should calculate this)
What causes increased QT interval? Why is this a problem?
Congenital syndromes Anti-psychotics Sotalol/amiodarone TCAs Erythromycin Hypokalaemia Hypomagnesaemia Hypocalcaemia
Predisposes to polymorphic VT
Where can U waves be seen? What can cause them?
Rhythm strip
Normal or hypkalaemia
What do ST changes in leads II, III and aVF indicate? Which artery is affected?
Inferior MI
Right coronary artery
What do ST changes in leads V1 - V4 indicate? Which artery is affected?
Anteroseptal MI
LAD artery
What do ST changes in leads V4-V5 and aVL indicate? Which artery is affected?
Anterolateral MI
LAD or L circumflex
What do ST changes in leads I, aVL +/- V5-6 indicate? Which artery is affected?
Left circumflex
What would a dominant R wave in V1-V2 and ST depression indicate to you?
Which artery would be affected?
Posterior MI
Left circumflex or Right coronary
What are key features of AF on an EGG?
Irregular
Without P waves
What are key features of atrial flutter on an ECG?
Regular
Saw-tooth base line (2:1, 3:1 and 4:1 block)
What are key features of atrial tachycardia on an ECG?
Regular
Abnormal P waves
What are key features of VF on an ECG?
no discernable P waves/QRS complexes (random wavy line)
NO PULSE
What are key features of VT on an ECG?
Broad complex tachycardia
What are key features of an atrial ectopic on an ECG?
narrow QRS with/without preceding ectopic p wave
What are key features of a ventricular ectopic on an ECG?
abnormal broad QRS at abnormal time
p occurs at predicted time
What are key features of WPW on an ECG?
slurred upstroke into QRS complex
Short PR interval
QRS complexes may be slightly broad
Dominant R wave in V1
What are key features of infarction on an ECG?
ST elevation (first change)
T wave inversion
Pathological Q waves (signify full-thickness MI)
After what time do pathological Q waves appear?
8-12 hours after ST elevation (if myocardium is not reperfused)
What are the STEMI criteria?
St elevation of >2 small squares in 2 adjacent chest leads
ST elevation of >1 small square in 2 adjacent limb leads
OR
new LBBB
What are key features of ischaemia on an ECG?
ST depression
new T-wave inversion
What are key features of previous infarcts on an ECG?
T wave inversion (weeks-months)
Pathological Q waves (permanent)
What are key features of hyperkalaemia on an ECG?
low flat P waves
Wide bizarre QRS
slurring into ST segment
tall-tented T waves
What are key features of hypokalaemia on an ECG?
small flattened T waves
Prolonged PR
Depressed ST
Prominent U wave
What are key features of hypercalcaemia on an ECG?
short QT
What are key features of hypocalcaemia on an ECG?
prolonged QT
What changes to an ECG might a PE cause?
tachycardia RV strain (RBBB, right axis deviation) RA enlargement (P pulmonale)
S1Q3T3 (prominent S wave in lead I, and Q wave and inverted T wave in lead III) - rare
What ECG changes are associated with pericarditis?
ST elevation in all leads PR depression (specific) saddle-shaped ST interval
Which leads show septal MI?
V1-2
Which leads show anterior MI?
V3-4
Which leads show lateral MI?
I + aVL
V5-6
Which leads show inferior MI?
II, III and aVF
Which leads show right ventricular MI?
V1
V4
