ECGs Flashcards
What is ECG evidence of hypokalaemia?
Inverted T waves followed by U waves (which are seen as humps, after the inverted T waves)
How do you differentiate between the ST depression associated with digoxin and NSTEMI?
In NSTEMI, ST-segment depression is horizontal, while in digoxin treatment the segment tends to be downsloping
What are signs on an ECG of a previous STEMI/MI?
Pathological Q waves
What suggests ischaemic changes in the heart on an ECG?
T-wave inversion
What are the effects of digoxin on ECG?
1) Downsloping ST depression/segments e.g. in leads V4-V6, I and aVL
2) T-wave changes (inversion)
3) Biphasic/flattened and shortened QT interval
4) Slight PR interval prolongation
5) Prominent U-waves
- these are NOT signs of digoxin toxicity
± signs of AF
What is the morphology of the QRS complex/ST segment with digoxin use described as?
Slurred, sagging, scooped and resembling either a reverse tick, hockey stick or Salvador Dali’s moustache
What is the characteristic feature on ECG of digoxin treatment?
Down-sloping ST segments (or reverse ticks)
Which condition can be confused with digoxin on ECG?
NSTEMI
AF ECG?
Irregularly irregular HR, no p waves
QRS complexes in right or left bundle branch block?
Broadened
Supraventricular tachycardia ECG?
Regularly regular rhythm, p wave sometimes not discernible
Atrial flutter ECG?
Saw-tooth baseline
What additional ECG changes can occur in hypokalaemia esp. < 2.7?
1) Widened P wave
2) Prolonged PR interval
3) ST depression
4) T wave inversion
5) U waves
6) Long QT/U interval
7) Premature ventricular complexes/supraventricular complexes
8) Supraventricular arrhythmias e.g. AF/flutter
9) Ventricular arrhythmias e.g. torsades de pointes, VT, VF
What is the relationship of hypokalaemia + hypomagnasaemia?
1) Concomitant hypomagnasaemia increases risk of arrhythmia with hypokalaemia - so check magnesium levels
2) Hypomagnasaemia can also cause hypokalaemia
Levels of which other electrolyte should you check in hypokalaemia?
Magnesium
What ECG changes occur in hyperkalaemia?
1) Tall tented T waves
2) Flattened P waves
3) Prolonged PR interval
4) Widened QRS complexes
5) Idioventricular rhythms
6) Sine wave patterns
7) VF/asystole
What must you always perform in hyperkalaemia?
ECG
How do you treat K > 6.5 or with any ECG changes?
1) 10% calcium gluconate (or chloride) 10ml over 10 mins (cardioprotective)
2) IV insulin (10U soluble) in 25g glucose (50ml of 50% or 125ml of 20% glucose) - causes intracellular K shift + glucose required to prevent hypoglycaemia
3) Nebulised salbutamol - causes intracellular K shift
What endocrine conditions cause hypokalaemia?
1) Hyperaldosteronism (Conn’s syndrome)
2) Cushing’s syndrome
What medications can cause hypokalaemia?
1) Diuretics - furosemide, thiazides
2) Beta agonists
3) Insulin
4) Theophylline
How do you manage mild hypokalaemia?
1) Oral slow release potassium chloride
2) Treat causes + check K regularly
How do you treat severe hypokalaemia?
1) Continuous cardiac monitoring
2) Check + correct magnesium (low Mg causes renal K wasting)
3) 1L IV 0.9% saline + 40mmol potassium chloride (max peripheral K infusion rate = 10 mmol/h, if faster rates required need central line)
4) Avoid glucose + bicarbonate
5) Treat cause
Which drugs cause hyperkalaemia?
1) ACEi/ARB
2) K sparing diuretics e.g. spironolactone
3) NSAIDs
4) Heparin/LMWH (inhibits aldosterone release)
5) Ciclosporin
6) High dose trimethoprim
7) Beta blockers
8) Digoxin
What endocrine condition causes hyperkalaemia?
Addison’s disease (adrenal insufficiency)
