ECG Case 006

Main Abnormalities

• The ECG shows widespread ST segment abnormalities.
• There is a biphasic appearance to the ST segments and T waves, with initial negative deflection (= ST segment depression / T wave inversion) followed by a terminal positive deflection (= U wave).
• All these waves merge into each other and it is difficult to tell where one wave ends and the other begins.
• There is gross prolongation of the QU interval (= time from onset of QRS complex to end of T/U wave).

Diagnosis 

The combination of…

• Widespread ST depression / T wave inversion
• Prominent U waves
• Long QU interval (> 500 ms)

…. is highly suggestive of severe hypokalaemia.

This patient had a serum K of 1.7 mmol/L in the context of decompensated Conn’s syndrome (primary aldosteronism).

Biphasic T waves may be seen with both myocardial ischaemia (Wellens syndrome) and hypokalaemia.

The main differentiating factor (apart from the clinical picture) is the direction of the T waves:

• Wellens: – biphasic T waves go UP then DOWN.
• Hypokalaemia: – T waves go DOWN then UP.

Wellens Syndrome

Hypokalaemia