ECGs

Question 1

What is ECG evidence of hypokalaemia?

Answer 1

Inverted T waves followed by U waves (which are seen as humps, after the inverted T waves)

Question 2

How do you differentiate between the ST depression associated with digoxin and NSTEMI?

Answer 2

In NSTEMI, ST-segment depression is horizontal, while in digoxin treatment the segment tends to be downsloping

Question 3

What are signs on an ECG of a previous STEMI/MI?

Answer 3

Pathological Q waves

Question 4

What suggests ischaemic changes in the heart on an ECG?

Answer 4

T-wave inversion

Question 5

What are the effects of digoxin on ECG?

Answer 5

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

Question 6

What is the morphology of the QRS complex/ST segment with digoxin use described as?

Answer 6

Slurred, sagging, scooped and resembling either a reverse tick, hockey stick or Salvador Dali’s moustache

Question 7

What is the characteristic feature on ECG of digoxin treatment?

Answer 7

Down-sloping ST segments (or reverse ticks)

Question 8

Which condition can be confused with digoxin on ECG?

Answer 8

NSTEMI

Question 9

AF ECG?

Answer 9

Irregularly irregular HR, no p waves

Question 10

QRS complexes in right or left bundle branch block?

Answer 10

Broadened

Question 11

Supraventricular tachycardia ECG?

Answer 11

Regularly regular rhythm, p wave sometimes not discernible

Question 12

Atrial flutter ECG?

Answer 12

Saw-tooth baseline

Question 13

What additional ECG changes can occur in hypokalaemia esp. < 2.7?

Answer 13

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

Question 14

What is the relationship of hypokalaemia + hypomagnasaemia?

Answer 14

1) Concomitant hypomagnasaemia increases risk of arrhythmia with hypokalaemia - so check magnesium levels
2) Hypomagnasaemia can also cause hypokalaemia

Question 15

Levels of which other electrolyte should you check in hypokalaemia?

Answer 15

Magnesium

Question 16

What ECG changes occur in hyperkalaemia?

Answer 16

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

Question 17

What must you always perform in hyperkalaemia?

Answer 17

ECG

Question 18

How do you treat K > 6.5 or with any ECG changes?

Answer 18

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

Question 19

What endocrine conditions cause hypokalaemia?

Answer 19

1) Hyperaldosteronism (Conn’s syndrome)
2) Cushing’s syndrome

Question 20

What medications can cause hypokalaemia?

Answer 20

1) Diuretics - furosemide, thiazides
2) Beta agonists
3) Insulin
4) Theophylline

Question 21

How do you manage mild hypokalaemia?

Answer 21

1) Oral slow release potassium chloride
2) Treat causes + check K regularly

Question 22

How do you treat severe hypokalaemia?

Answer 22

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

Question 23

Which drugs cause hyperkalaemia?

Answer 23

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

Question 24

What endocrine condition causes hyperkalaemia?

Answer 24

Addison’s disease (adrenal insufficiency)

Question 25

What are causes of hyperkalaemia by increased release from cells?

Answer 25

1) Lactic acidosis
2) Insulin deficiency
3) Rhabdomyolysis
4) Tumour lysis syndrome
5) Massive haemolysis
6) Digoxin toxicity (can be precipitated by hypokalaemia)
7) Beta blockers