Young adult patient presenting with syncope. History of eating disorder. Describe the ECG.

TOP 100 ECG QUIZ LITFL 031 3

Describe and interpret this ECG

ECG ANSWER and INTERPRETATION

Main Abnormalities

ECG Hypokalemia Long QU interval Torsades

Diagnosis

The combination of…

  • Atrial ectopy
  • Prominent U waves
  • Long QU interval
  • Torsades de Pointes

… is strongly suggestive of severe hypokalaemia. This patient had a K of 1.9 mmol/L.

Hypokalaemia occurs in eating disorders via multiple mechanisms including:

  • H+ is lost in vomiting — renal distal tubular reabsorption of H+ occurs in exchange for K+ (primary mechanism)
  • Loss of K+ in bodily secretions — vomiting, purging with laxatives or diuretics
  • Reduced oral intake
  • Metabolic alkalosis from vomiting causing intracellular shifts of K+
  • Hypovolaemia causing secondary aldosteronism with renal loss of K+

CLINICAL PEARLS

U wave morphology

The appearance of U waves in hypokalemia may vary. This example demonstrates discrete U waves that are clearly distinguishable from the T wave.

Compare this with Quiz ECG 006, where the whole ST-T-U complex is fused together to produce a “rollercoaster” appearance, with the U wave appearing as a positive deflection that emerges from a negative ST segment and T wave.

Discrete U waves

Discrete U waves

“Rollercoaster” U waves

“Rollercoaster” U waves

TOP 100 ECG SERIES


Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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