ECG Interpretation Flashcards
What are the things you need to report in order?
- HR
- Rhythm
- Cardiac Axis
- P-waves
- PR interval
- QRS complex
- QT interval
- ST segment
- T waves
- U waves
What do you need to identify on the ECG before starting your interpretation?
Name
DOB and Age
Time and Date of ECG
Was the patient experiencing any chest pain?
Settings (paper speed 25mm/s, 10mm/mV deflection)
What are the big and small squares equal to in time?
Small 0.04s
Big 0.2s
What are the parts of a wave and what do they mean?
P QRS T (U)
P - depolarization of the atria, from right to left
PR - time the electrical impulse takes to travel from the sinus node through the AV node
QRS - rapid depolarization of the right and left ventricles
QT - the period when the ventricles are depolarized
ST - the period when the ventricles are polarized
T - repolarization of the ventricles as above
U - theoretical
What BPM is tachycardia?
> 100bpm
What BPM is bradycardia?
<60bpm
How is HR calculated?
or 300/ss between complexes
Number of complexes x6
How is rhythm assessed?
P waves preceding each QRS complex? - Sinus
Rhythm regularly irregular? - 2nd degree heart block (AV block)
Irregularly irregular? - Atrial fibrillation
Or AV dissociation - P independent from QRS
How is cardiac axis assessed?
Measured the overall direction of electrical burst
Should go from 11 o’clock to 5 o’clock
Look at leads I, II and III.
I and II positive - normal axis (lead 2 most +ve)
III and II positive - right axis deviation (lead III most +ve)
III and II negative - left axis deviation
What does right axis deviation indicate?
Right ventricular hypertrophy, pulmonary embolism (pseudo left), anterolateral MI
What does left axis deviation indicate?
Left ventricular hypertrophy, inferior MI, Wolff-Parkinson-White syndrome
What is the organisation of coronary blood vessels?
a
What are the contiguity of the leads?
(I - lateral) (aVR -
(II - inferior)
(III - inferior)
How are P-waves assessed?
Present? - no atrial fibrillation
Is each one followed by a QRS?
Normal? <2.5 mm high, <0.12s or 3ss (Lead II)
- Monophasic in lead I, biphasic in V1
-The first 1/3 of the P wave corresponds to right atrial activation, the final 1/3 corresponds to left atrial activation; the middle 1/3 is a combination of the two
Higher P wave, same width - P-pulmonale, right atrial hypertrophy/enlargement
Wider P wave, same height, may be bifurcated - P-mitrale, left atrial hypertrophy/enlargement
Sawtooth
Chaotic
Flat
How is the P-R interval assessed?
From beginning of P to start of QRS complex
0.12-0.2 (3-5ss)
If longer suggest AV block
First degree heart block - fixed prolonged
Second degree type 1 heart block (Mobitz I) - progressive prolongation until dropped
Second degree type 2 heart block (Mobitz II) - intermittent dropping every 3rd (3:1) or 4th (4:1) wave
Third degree (complete) - no association between P and QRS
-QRS complex <0.12s originates from above bundle of His bifurcation
->0.12s originates from below the bundle of His bifurcation
If shorter the impulse may be originating closer to the AVN or travelling faster via an accessory pathway rather than the atrial wall (delta wave-slurred QRS uptake).
First-degree AV block:
Occurs between the SA node and the AV node (i.e. within the atrium).
Second-degree AV block:
Mobitz I AV block (Wenckebach) occurs IN the AV node (this is the only piece of conductive tissue in the heart which exhibits the ability to conduct at different speeds).
Mobitz II AV block occurs AFTER the AV node in the bundle of His or Purkinje fibres.
Third-degree AV block:
Occurs at or after the AV node resulting in a complete blockade of distal conduction.
How is the QRS complex assessed?
- Width <0.12s> - broad is conduction defect e.g. Bundle Branch Block, narrow is supraventricular associated with flutter waves (atrial flutter)
- Height 5-30mm - tall equals LVH
- Morphology - delta waves
Look up extra morphology
How is the Q-T interval assessed?
From start of QRS to end of T.
Can be prolonged in acute myocardial ischaemia, myocarditis, drugs and head injury.
How is the J point assessed?
It is where the S wave meets the ST segment.
Can be raised in benign early repolarisation, don’t confuse with ST elevation.
How is the S-T segment assessed?
Should be at the isoelectric line
Elevation >1ss from baseline is significant and indicates acute MI
Depression may be caused by anxiety or tachycardia
How are the T-waves assessed?
Normally inverted in AVR, V1 and III
Tall - hyperkalaemia, hyper-acute STEMI
Inverted - previous ischaemia, BBB, PE
Biphasic - ischaemia, hypokalaemia
Flattened - electrolyte imbalance, ischaemia
What are U waves?
Small deflections after T waves which indicate electrolyte imbalance, hypothermia, drug toxicity
Where are the 4 extra leads placed?
RA. On the right arm, avoiding thick muscle.
LA In the same location where RA was placed, but on the left arm.
RL On the right leg, lower end of inner aspect of calf muscle. (Avoid bony prominences)
LL In the same location where RL was placed, but on the left leg.
