Wednesday, 11 October 2017

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.





Click to enlarge
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

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