ECG of the Week - 9th October 2017 - Interpretation

The following ECG is from a 64 yr old female who presents feeling generally unwell and weak. She has a history of pituitary lesion treated by surgical resection and radiotherapy.

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Rate:

• 48 bpm

Rhythm:

• Regular
• Sinus rhythm

Axis:

• Normal

Intervals:

• PR - Normal (~160ms)
• QRS - Normal (100ms)
• QT - 480ms (QTc Bazette 430 ms)
• Note the ECG machine calculated the QT 500ms / QTc 480ms
• Likely due to low T wave voltage plus T-U fusion

Additional:

• Subtle ST depression in leads II, aVF
• U wave visible in leads V2-3
• T waves globally flat
• Relatively long ST segment

Interpretation:

• Changes consistent with electrolyte abnormality - differentials: 
• Hypokalaemia - U waves, T-U fusion with QT prolongation, ST depression, low voltage T waves
• Hypomagnesaemia - associated with hypokalaemia
• Hypocalcaemia - causes long QT due to ST segment lengthening

What happened ?

The patient's K was 2.7 mmol/L with a low-normal magnesium and low-normal calcium. Following IV electrolyte replacement the patients ECG changes resolved and her symptoms of weakness also resolved. 

Post pituitary surgery and/or radiotherapy complications

Surgical complications

• GA complications
• CSF leak
• CNS infection
• Post resection pituitary apoplexy
• Hydrocephalus
• Epistaxis
• Olfactory sensory loss

Radiotherapy complications

• Radiation toxicity - hypothalmic & chiasmal necrosis
• Dermal changes

Endocrine complications

• Central Diabetes Insipidus
• SIADH
• Adrenal insufficiency
• Hypothyroidism
• Gonadotropin deficiency

References / Further Reading

Life in the Fast Lane

• Hypokalaemia

Textbook

• Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.