ECG Flashcards
What does L axis deviation mean from the pathological (simple) point of view?
L axis deviation = more electricity goes to the L side of the hear
How does L axis deviation look on ECG?
L = leaving (positive in lead I and negative in lead II) = point away from each other
Causes for L axis deviation
L axis deviation = increased electricity to L side of the heart
Causes:
- L ventricular hypertrophy
- Wolf-Parkinson White syndrome
- VT
- LBBB
- inferior MI
- L anterior hemiblock
How does R axis deviation look like on ECG?
R = returning (lead I is negative and lead II is positive) -> the ways point towards each other
What R axis deviation mean and what are possible causes?
R axis deviation = more electricity goes towards R side of the heart
Causes: tall and thin body type, RV hypertrophy (e.g. in PE, pulmonary disease), lateral MI, WOlf-Parkinson White Syndrome)
How high P wave should be?
What does it mean if it is higher than that?
P wave should be =/< 2 small squares
If it is higher than that -> R atrial enlargement e.g. in pulmonary hypertension
What are possible pathological appearances of P wave? (morphology)
- bifid
- peaked
How does bifid P wave looks like?
Bifid
looks like ‘m’ = P mitrale (left atrial enlargement - caused by mitral stenosis)
How does ‘peaked’ P wave look like? What is its cause?
Peaked = P pulmonare
*classically seen in R atrial enlargement in lung disease
What’s the normal length of PR interval?
PR interval should be 3-5 small squares
When PR interval is decreased?
PR interval decreased in: accessory conduction pathways (e.g. WPW syndrome)
When PR interval is increased?
PR interval increased in AV node block (‘heart block’)
Causes of heart block
- athletes /increased vagal tone
- electrolyte disturbances
- Drugs that block AV node: B - blockers, digoxin, CCB
- conduction system fibrosis
- Inferior MI
- autoimmune disease (SLE, systemic sclerosis)
- inflammatory diseases (myocarditis, RF)
- infiltrative conditions (amyloidosis, haemochromatosis)
Size of normal Q wave
Normal Q waves = small Q wave:
- <1 small square wide
- <2 small squares deep
What leads normal Q waves can be found in?
Normal Q wave (small; <1 sq wide, <2 sq deep)
Found in: I, aVL, and V6 -> due to septal depolarization
What do pathological Q waves mean?
Established/previous full thickness MI
What is a normal R wave progression across ECG?
Negative in V1 (dominant S wave) -> mostly positive in V6 (dominant R)
What’s transition point?
Leads where R and S are equal -> usually V3/V4
What’s the clockwise rotation and what’s its cause?
Clockwise rotation = transition point after V4
Cause: R ventricular hypertrophy e.g. in chronic pulmonary disease
What’s ‘M’ pattern in bundle blocks?
RSR’
Potential causes of RBBB
RBBB:
- R ventricular hypertrophy
- cor pulmonare
- PE
- atrial-septal defect
- IHD
- cardiomyopathy
Possible causes for LBBB
- aortic stenosis
- IHD
- hypertension
- anterior MI
- cardiomyopathy
- conduction system fibrosis
- hypercalcaemia
Pattern seen on LBBB
W illia M
W on V1
M on V6
Pattern seen on RBBB
M arro W
M - V1
W - V6
What is the disgnosis if: RSR’ pattern seen with a normal QRS length?
Partial (incomplete) bundle branch block - no clinical significance
(normal QRS length is <3 sq)
ST segment elevation:
- convex or straight
- concave
- concave/saddle shaped
Causes
- Convex/ straight -> infraction
- concave -> early repolarisation, LVH
- saddle shaped -> pericarditis, tamponade
What does ST elevation that is downwards slopping/ ‘reverse tick’ mean?
Digoxin toxicity
In which leads T inversion is normal?
It can be normal in leads: III, aVR and V1 (right leads)
This is due to the angle from which they view the heart
Also, in Afro-Caribbean: V2-3
T inversion in leads other than normally seen - causes
- ischaemia/post MI
- PE
- RL ventricular hypertrophy
- bundle branch block
- digoxin use
What does tented T wave mean?
hyperkalemia
What do flat T waves mean?
hypokalaemia
Biphasic T wave - cause
Biphasic
- ischaemia (up then down)
- hypokalaemia (down then up)
Regions on ECG
Corrected QT interval
- value
- how to calculate
- significance
<450 ms
- calculated by ECG machine or by use of online calculator
- if it is increased -> predisposition to polymorphic VT
Causes of prolonged QT inerval
- congenital syndromes
- antipsychotics
- sotalol/amiodarone (class III)
- TCAs
- macrolides
- hypokalaemia/hypomagnesaemia/ hypocalcaemia
Causes of U waves
- can be normal
- hypothermia
- hypokalaemia
- use of anti-arrhythmia
The sequence of ECG interpretation
- Personal details: name, DOB
- Date
- Symptoms (e.g. chest pain)
- calibration
- Rate and rhythm
- Axis
- P wave
- PR interval
- QRS complex
- ST segment
- T wave
- Other things: corrected QT interval, U waves
Pathological changes on ECG in STEMI (in order)
