ECG Flashcards
Inferior leads
Lead 2,3 and aVF
Lateral leads
1, aVL, aVR, V5-6
Septal leads
V1, V2
Anterior leads
V3-V4
Order of reading ECG
- Patient details
- Heart rate
- Heart rhythm
- Cardiac axis
- P waves
- PR interval
- QRS complex
- ST segment
- T waves
- U waves
Normal heart rate and how to measure
60 to 100bpm
300 / RR interval (big squares)
If irregular - no of complexes on rhythm strip (6 secs = 30 boxes) x 10
Assessing heart rhythm
Regularly regular
Irregularly irregular
Cardiac axis
Leaving - left axis deviation (leads 1+2)
Arriving - right axis deviation
P wave assessment
Present
Followed by QRS
Duration, direction, shape
Sawtooth =flutter
Chaotic = fibrillation
PR interval assessment
Prolonged = more than 200ms (1 large square)
Shortened = less than 120ms (3 small boxes)
Delta wave
Wolff-Parkinson syndrome if occurs with tachycardia
Slurred upstroke of R wave
QRS complex assessment
- Width - broad if >120ms (3 small squares)
- Height - tall if >5mm (1 large square) in limbs and >10mm (2 large squares) in chest
- Delta wave
- Pathological q wave- >25% of size of R wave />2mm in height (2 small squares) + > 40ms in width (1 small squares) in V1-V3
- R/S waves - S>R until V3/4
- J point (looks like ST elevation)
ST segment
Elevation - >1mm (1 small square) in 2+ contiguous limb leads or >2mm (2 small squares) in 2+ chest leads
Depression - > 0.5mm (half small square) in 2+ contiguous leads
T waves
Tall - >5mm (1 large square) in limbs and >10mm (2 large squares) in chest
Inverted - normal in V1 and 3
Biphasic
Flattened
U wave
Rare
>0.5 (half small square) deflection after t wave
In V2/3
First degree heart block
Fixed prolonged PR interval
Second degree heart block
Mobitz type 1/ Wenckebach phenomenon - progressive prolonging of PR interval followed by absence of QRS
Mobitz type 2- constant PR interval, absent QRS every 3 to 4 waves (3:1 or 4:1)
Acute MI / chronic heart disease
Third degree heart block
No relationship between p waves and QRS complexes - more p waves than QRS
Right axis deviation
Variable PR intervals
MI
Fibrosis
Consider pacemaker
Right bundle branch block
Normal PR interval
Broad QRS (>120s)
Second R wave (slow depolarisation on RHS) (R1)
MaRroW
V1 - M shape - +ve R, -ve S, +ve R1
V6 - W shape - -ve R, +ve S, -ve R1
Wide slurred S wave in lateral leads
Left bundle branch block
Normal PR interval
Broad QRS
WilLiaM
Dominant S wave in V1
Broad monophonic R wave in lat leads
Absence of q waves in lat leads
Prolonged R wave in lateral leads
Sinus rhythm
One p wave per QRS
Constant PR interval
Causes of BBB
Aortic stenosis
MI
Sinus tachycardia
Exercise
Dear
Pain
Haemorrhage
Thyrotoxicosis
Sinus bradycardia
Athletic training
Fainting
Hypothermia
Myxoedema
Immediately after MI
Locations of rhythm abnormality
SAN
AVN (nodal/junctional)
Ventricular muscle
Supraventricular rhythms
Rhythm that originates outside of ventricles and spreads in normal manner
Can be atrial or nodal
Normal QRS
Atrial escape
SAN node does not start depolarisation
Another part of atrium does
Abnormal p wave
Normal QRS
Normal beats after abnormal one
Nodal escape
No p waves
Normal QRS
Bradycardic
Ventricular escape
Seen in complete heart block / one offs
SAN and junctional escape fails
No p wave
Normal rhythm afterwards
Accelerated idioventricular rhythm
Ventricular rhythm but not bradycardic - normal rhythm
Benign
Extrasystoles
Similar to escape rhythms
But beat occurs earlier rather than later than expected
Junctional extrasystole
absent / misplaced p wave
As depolarisation travels to atria and ventricle at same time
Normal QRS
Atrial extrasystole
Normal beat but earlier than expected
Tachycardia
Either atrium or AVN depolarising too quickly
Look at p wave to discover origin
If intermittent = paroxysmal
Atrial tachycardia
p waves superimposed on the t waves of preceding beat
QRS normal
AVN limit is 200bpm - if atrial depolarisation faster - AV block
But block has sinus rhythm (no tachycardia)
Atrial flutter
Rate > 250bpm
Saw tooth p waves
Associated with block
Nodal tachycardia
P waves very close to QRS or no p waves
QRS normal
Carotid sinus pressure - stimulate AVN and SAN - no effect on ventricular tachycardias
Ventricular tachycardia
Broad QRS
Difficult to identify t waves
No p waves
Regular QRS
similar to BBB
If just had MI - VT
Atrial fibrillation
No p waves
Irregularly irregular
Tachycardia
Ventricular fibrillation
No discernable pattern
Very likely to lose consciousness
Urgent defibrillation
Wolff-Parkinson-White syndrome
Accessory pathway from atria to ventricles on LHS (bundle of kent)
Pre-excitation of ventricles
Risk of sudden death if paroxysmal tachycardia - loop of depolarisation / re-entry circuit
R axis deviation
Short PR and QRS
Delta wave
If tachycardic = no p waves
Pacemaker
Occasional p waves not related to QRS
QRS preceeded by spike
Broad QRS as depolarisation is ventricular in origin
Ectopic beats
Unexpected p waves (atrial) or QRS (ventricular)
Atrial ectopics
Abnormal or no p wave
Normal QRS
Benign
Ventricular ectopics
Widened QRS
Irregularly irregular pulse
Benign
Predispose to VT
Hyperkalaemia
Peaked t wave
Wide/flat p waves
Bradycardia
Conduction blocks
QRS widening
Hypokalaemia
Tall p wave
Prolonged PR interval
ST depression
T wave flattening/inversion
U waves
Long QT interval due to fusion of T and U waves
