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ECG in

Electrolyte

AbnormalitiesThe faces of ECG series

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Potassium

Serum potassium level may be deceiving

o Acute changes are likely to lead to ECG changes

o

Chronic changes often result in no orminimal ECG changes

Correlation between potassium level and ECG

changes is unreliable

Sensitivity in detecting hyperkalaemia is low

Wrenn KD, Slovis CM, Slovis BS. The ability of physicians to predict hyperkalemia from the ECG. Ann Emerg Med 1991;20:1229-32.

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Case ExampleA 17yo girl is known to suffer

with anorexia nervosa, and

purgative misuse, presented

in ED as she complained shehad felt very weak, and had

not been able to get out of

bed.

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Case ExampleA 17yo girl is known to suffer

with anorexia nervosa, and

purgative misuse, presented

in ED as she complained shehad felt very weak, and had

not been able to get out of

bed.

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Case ExampleA 17yo girl is known to suffer

with anorexia nervosa, and

purgative misuse, presented

in ED as she complained shehad felt very weak, and had

not been able to get out of

bed.

Potassium 1.8mmol/L

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Hypokalaemia

D E F

T U

UT UT U

A B C

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HypokalaemiaLarge P wave T wave flattening Prominent U wave

ST depression

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Hypokalaemia

PR prolongation

QTc prolongation T wave often merges with U wave

Increased risk of VT

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Case Example62yo Maori woman with

DMT2. She is on dialysis

for CKD. 24hrs worsening

nausea and vomiting.She missed one session as

she briefly visited family

in New Zealand.

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Case Example62yo Maori woman with

DMT2. She is on dialysis

for CKD. 24hrs worsening

nausea and vomiting.She missed one session as

she briefly visited family

in New Zealand.

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Case Example62yo Maori woman with

DMT2. She is on dialysis

for CKD. 24hrs worsening

nausea and vomiting.She missed one session as

she briefly visited family

in New Zealand.

Potassium 8.1mmol/L

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Case Example53yo man DMT1, CKD on

dialysis. GCS 10. D2 post

dialysis next session

tomorrow. BSL >38mmol/L.Dry gangrene of toes and

middle finger.

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Case Example53yo man DMT1, CKD on dialysis. GCS 10. D2 postdialysis next session tomorrow. BSL >38mmol/L. Drygangrene of toes and middle finger.

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Case Example53yo man DMT1, CKD on dialysis. GCS 10. D2 postdialysis next session tomorrow. BSL >38mmol/L. Drygangrene of toes and middle finger. K 8.6mmolL

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Hyperkalaemia

Flat P wave Increased PR Wide QRS Peaked T wave

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HyperkalaemiaSine wave appearance

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Hyperkalaemia

Increased amplitude and peaking of T wave

QRS prolongation

PR prolongation P wave flattening

Loss of P wave

Sine wave appearance

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Case ExampleA 56yo woman has recently

had a bout of viral gastro she

had thyroidectomy 3 weeks

ago. She is fatigued, hasmuscle cramps in the arms

and tingling in the toes.

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Case ExampleA 56yo woman has recently had a bout of viral gastroshe had thyroidectomy 3 weeks ago. She is fatigued,has muscle cramps in the arms and tingling in thetoes.

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Hypocalcaemia QTc prolongation

Ca deficiency Prolonged QTc interval

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Hypocalcaemia Terminal T wave inversion

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Hypocalcaemia

QTc prolongation

ST segment prolongation

P wave normal PR interval normal

Rate usually not affected

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Case ExampleA 63yo Lao man with lung

cancer. He is complaining

of anorexia, nausea, poliuria

and polydipsia. He isconstipated too.

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Hypercalcaemia

QTc shortening Biphasic T wave

Osborn wave

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Hypercalcaemia

P and T waves usually unaltered

Ventricular fibrillation may occur in severehypercalcaemia

QT interval correlates with severity ofhypercalcaemia

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The End