CVS 7 ECG Flashcards
What colours are the limb electrodes?
Ride Your Green Bike
RA - Red
LA - Yellow
LL - Green
RL - Black
Where are the 6 chest electrodes placed?
V1- 4th intercostal space to right of sternum
V2- 4th ICS to left of sternum
V3- halfway between V2+V4
V4- 5th ICS at the midclavicular line
V5- level with V4 at the left anterior axillary line
V6 - level with V4+5 at left mid axillary line
(directly under midpoint of armpit)
Location of V1 electrode
4th intercostal space to right of sternum
Location of V2 electrode
4th intercostal space to left of sternum
Location of V3 electrode
Halfway between V2 + V4
Location of V4 electrode
5th intercostal space at midclavicular line
Location of V5
Level with V4 at left anterior axillary line
Location of V6 electrode
Level with V4+5 at left mid axillary line
(Directly under midpoint of armpit)
How do the ECG leads work?
Each lead is a representation of a measurement of the change in mV in 2 electrodes
Signal for each of the 12 leads represents change over time
Each lead represents specific part of the heart
What does 1 small square on an ECG represent?
0.04 seconds (40ms)
What does 1 large square on an ECG represent?
0.20 seconds
What is 1 second on an ECG?
5 large squares
How should you approach an ECG?
Correct patient?
Rate- 10 second strip - QRS waves x 6 = HR
Rhythm
Axis
Intervals
What gives you lead I?
Difference between RA + LA
What gives you lead II?
Difference between RA + LL
What gives you lead III?
Difference between LA + LL
What are the augmented leads?
avR
avF
avL
What type of wave is generated if signal is going directly - to + ?
Strong upwards deflection
What type of wave is generated if signal is going partially - to + ?
Small upwards deflection
What type of wave is generated if signal is going perpendicular - to + ?
Biphasing
Positive and negative
What type of wave is generated if signal is going away at an angle - to + ?
Small downward deflection
What type of wave is generated if signal is going directly away - to + ?
Strong downwards deflection
Anterior/septal leads
What artery is affected?
Septum V1+V2
Anterior V3+V4
Left anterior descending artery
Lateral leads
What artery is affected?
I
avL
V5
V6
L - lateral
1+5+6=12 L is the 12th letter of the alphabet
Left circumflex or left anterior descending
Inferior leads
What artery is affected?
Lead II
Lead III
avF
INF
N - 2 vertical lines»_space; lead II
IN - 3 vertical lines»_space; lead II
F»_space; avF
Right coronary artery or left circumflex
What is the axis of the ECG?
Top right - to bottom left +
What is sinus rhythm?
Regular spacing with same QRS and P waves before
What is sinus arrhythmia?
Irregular spacing between QRS with a p wave before QRS
Describe atrial fibrillation
Irregular irregular
Irregular spacing with no p wave
Atria quiver rather than properly contracting
Length of a normal PR interval
0.12-0.2 seconds
What are the colours of the chest electrodes?
Ride Your Great Big Brown Pony
Red
Yellow
Green
Brown
Black
Purple
Left side of the heart leads
Lead I
avL
What is sinus bradycardia?
Sinus rhythm with <60bpm
What is sinus tachycardia?
Sinus rhythm with >100bpm
How to calculate heart rate from ECG with regular rhythm?
300/no. of large boxes between complexes
How to calculate rhythm of ECG with irregular rhythm?
No. of QRS complexes in 10 seconds x 6
What are wider QRS waves associated with?
Abnormal ventricular depolarisations
What are longer PR intervals indicative of?
What length is long?
slow conduction from atria to ventricles
1st degree branch block
Ischaemic heart disease
Hypokalaemia
>0.2 seconds
What are shorter PR intervals indicative of?
What length is short?
Wolf-Parkinson-White (delta wave seen)
<0.12seconds
What factors affect the amplitude of deflection?
- Size + speed of muscle changing potential
- Direction of wave activity towards electrode
What structures compose the specialised conducting system of the heart?
SAN
AVN
Bundle of His
Right + left bundle branches
Purkinje fibres
What is avL being the greatest positive lead indicative of?
Left axis deviation
What is lead III being the greatest positive lead indicative of?
Right axis deviation
How do you confirm left axis deviation?
avL - greatest positive lead
Leads II,III + avF - negative
How do you confirm right axis deviation?
avF - most positive lead
Lead I + avL - negative
What is seen in Wolf-Parkinson-White syndrome?
Delta wave
Short PR interval
What are the characteristics of first degree heart block?
Causes
Consistently prolonged PR interval
> 5 small squares
QRS complex follows
Causes - ischaemic heart disease
hypokalaemia
What is characteristics of Mobitz Type 1 (second degree heart block)?
Progressive lengthening of PR interval
1 QRS wave drops
Cycle repeats
What is characteristic of Mobitz Type 2 (second degree heart block)??
PR interval normal
Sudden non conduction of beat
Dropped QRS
What causes complete heart block?
- normal atrial depolarisation but impulses not conducted to ventricle
- ventricular pacemaker takes over
What is characteristic of third degree heart block?
Very slow rate 30-40bpm»_space; BP can’t be maintained
Wide QRS complex
No relationship between P wave and QRS complex
What is seen in right bundle branch block?
Bunny rabbit ears in V1
QRS prolonged >3 small squares
How do you find the 4th intercostal space?
Find the sternal angle - slight dip in between manubrium + body of sternum
- this give you the 2nd ICS, count down to the 4th
Describe the cardiac conduction pathway and deflections
- depolarisation towards the electrode = upwards deflection (when
impulse is travelling down the septum, this gives the upwards part of
QRS complex - depolarisation away from the electrode = downwards deflection
(impulse travelling up ventricles giving downwards part of QRS complex - repolarisation towards electrode = downward deflection
- repolarisation away from electrode = upward deflection
how can you look at an ECG orderly to determine if it is normal
- calculate the heart rate
- is the rhythm regular or irregular (mark them out with peaks of QRS complex and slide across to match it up if unsure
- are there P waves - this suggests atrial activity
- are there QRS complexes - this suggests ventricular activity
- is each P wave followed by a QRS complex and is each QRS complex preceded by a P wave
- measure the intervals of
PR, QRS and QT
Change in ECG following a STEMI
1- normal ECG
2- hyper acute T wave
3- ST elevation
4- deeper Q wave inverted T wave
5- improved ST elevation
6- Q wave persists + T wave normalises
What is a STEM?
Full thickness myocardial infarction
ST elevation myocardial infarction
What is an NSTEMI?
Partial thickness myocardial infarction
Non ST elevation myocardial infarction
What is seen on the ECG of a NSTEMI?
Depressed ST segment
Inverted T wave
ECG of atrial flutter
Sawtooth pattern in inferior leads
ECG in hypokalaemia
First sign - T wave inversion
ST depression
Prominent U wave
ECG in hyperkalaemia
Peaked T waves
P waves flattening
PR prolongation
Wide QRS complex
What features are seen on an ECG with ectopic beats?
Atrial ectopic - early abnormally shaped P wave
**Atrioventricular junctional ectopic ** - inverted P wave
Ventricular ectopics - broad QRS complex
Causes of heart block
Fibrosis
Ischaemia
ECG of 2:1 block
For every 2 P waves
There is only 1 QRS complex
How do you determine if an ECG is in sinus rhythm?
If each P wave is followed by a QRS complex
Describe Torsades de Pointes
Polymorphic ventricular tachycardia
QRS complex all look different
Long QT interval
Most common cause of left axis deviation
Defects in conduction system
Most common cause of right axis deviation
Right ventricular hypertrophy
