ECG Interpretation Flashcards
What does one small square on an ECG represent?
1mm (0.04 seconds)
What does one large square on an ECG represent?
5mm (0.2 seconds)
How do you calculate a heart rate from an ECG?
If regular - count number of large squares between R-R interval and divide 300 by this number
If irregular - count number of QRS complexes on one strip and times by 6
How do you determine normal cardiac axis from an ECG?
Lead I, II and III are all positive
Lead II is the most positive
Lead avR is the most negative
How do you determine right axis deviation from an ECG?
Lead I is negative
Lead II and III are positive
Most positive is lead III
What is the most common cause of right axis deviation?
Lead I is positive
Lead II and III are negative
Lead I is most positive
Usually due to conduction abnormalities
What most commonly causes an absent P wave?
Atrial fibrillation
How long should a PR interval be?
3-5 small squares
Should be no more than one large square (0.2s)
What does a prolonged PR interval suggest?
Heart block
What is first degree heart block? How is it managed?
Prolonged PR interval
No management needed
What is second degree heart block type 1?
How is it managed?
Progressive prolongation of the PR interval until a dropped QRS
No management needed
What is second degree heart block Mobitz type 2? How is it managed?
Constant prolongation of PR interval with intermittently dropped QRS
Management = Permanent pacemaker
What is third degree heart block?
No association between PR interval and QRS complex
QRS complex= usually regular
Management= permanent pacemaker
What is a significant ST elevation?
> 1mm in 2 or more limb leads
>2mm In 2 or more chest leads
What does ST elevation in leads V1-V4 signify?
Anteroseptal MI
LAD
What does ST elevation in I, avL, V5 and V6 signify?
Lateral MI
Left circumflex artery
What does ST elevation in leads II, III, aVF indicate?
Inferior MI
Right coronary artery
X
X
Which electrolyte disturbances can cause long QT syndrome ?
Hypocalcaemia Hypokalaemia Hypomagmasaemia Hypothermia Hypothyroidism
Which drugs can cause long QT syndrome ?
METHCATS Methadone/Methotrexate Erythromycin Terfenadine Haloperidol Citalopram Amiodarone Tricyclics Sotalol
How do you determine left axis deviation from an ECG?
Lead I is positive
Lead II and III are negative
Lead I is most positive
Usually due to conduction abnormalities
Which electrolyte abnormality is associated with tall T waves?
Hyperkalaemia
What ECG changes are seen in hyperkalaemia?
Tall tented T waves
Widened flattened P wave
Prolonged PR interval
Broad QRS
Severe:
Sinusoidal wave pattern
V fib
What is seen on ECG in left bundle branch block?
Wide QRS complex
WiLLiaM
V1 = W = rS
V6 = M
What is seen on ECG in right bundle branch block?
Wide QRS complex
V1 = M = RSR
V6 = W = rS
MaRRoW
Which leads is it normal for the T wave to be inverted?
Lead V1 and avR
Can also be normal in lead I, avL and V6
Can also be normal in lead III
What are the two types of tachycardia?
Narrow complex and broad complex
What are the two types of ventricular tachycardia?
Monomorphic and polymorphic
What is the main cause of monomorphic ventricular tachycardia?
Myocardial infarction
What is an example of polymorphic ventricular tachycardia?
Torsades de pointes (caused by long QT)
How does atrial fibrillation present on an ECG?
Irregularly irregular rhythm
Absence of P wave
Narrow complex
How does hypokalaemia present on an ECG?
U waves
Small/absent T waves
Prolonged PR interval (same as hyperkalaemia)
How is Wolff-Parkinson White Syndrome seen on an ECG?
Short PR interval
Broad QRS
Delta wave
Left or right axis deviation
Pseudo-Q waves
How can Digoxin use affect an ECG?
U waves
Short QT interval
Downward sloping ST depression
T wave flattening
Arrhythmias - AV block
What are causes of RBBB?
Right ventricular hypertrophy
PE
MI
How does hypothermia present on an ECG?
Jesus Quist It’s Bloody Freezing
J waves
QT prolongation
irregular
Bradycardia
First degree block
Also: Torsades de pointes
How can Wolff-Parkinson White be treated?
Radiofrequency ablation of the accessory pathway
What is a ventricular ectopic?
A premature ventricular beat causes by random electrical discharges
Seen on ECG as an individual random broad QRS complex
What ECG change is seen in cardiac tamponade?
Electrical alternans (alternating QRS amplitude)
How is torsades de pointes treated?
IV Magnesium sulfate, Cardioversion
How can raised ICP show on an ECG?
Long QT
What ECG change can be seen in rheumatic fever?
P mitrale due to mitral stenosis
Prolonged PR
What are indications for cardiac re-synchronisation therapy in heart failure?
Widened QRS complex on ECG
Usually last resort
What is normal QT length?
No more than 11 small squares
What is normal QRS length?
No more than 0.12s (3 small squares)
Normal = around 2 small squares
What is a bi-fascicular block?
RBBB + Left axis deviation
What is a tri-fascicular block?
RBBB + Left axis deviation + 1st degree heart block
What is the difference between 2:1 and 3:1 atrial flutter?
2: 1 = 2 flutters to each QRS
3: 1 = 3 flutters to each QRS
What precipitates Torsades des Pointes?
Long QT
How is a posterior MI seen on ECG?
Reciprocal changes in V1-V3 : ST depression Tall broad R waves Upright T waves Dominant R wave in V2
In which leads do you get reciprocal changes (ST depression) for each type of STEMI?
PAILI (Posterior, anterior, inferior, lateral, inferior)
You get reciprocal changes in area after
E.g. Anterior MI you get inferior reciprocal changes
Which ECG leads are the limb leads?
I, II, III
avR, avL, avF
What can be the first sign of a STEMI on ECG?
Hyperacute T waves
