Gitelman’s Syndrome: Hypokalæmia

Report:

Sinus rhythm 85/min

Right axis deviation +140o

Right bundle branch block

Large TU waves c/w hypokalæmia

Comment:

This is, almost, a P-on-U phenomenon (no pun intended), as Schamroth put it11. The diagnosis can only be made, as reported, in a context of known hypokalæmia (1.4 mEq/L at the time of the recording). Otherwise, long QT interval or “cerebral” TU waves are a possibility. There is no clear separation of T and U waves in any lead. Indeed, the QTc may itself be prolonged here, because of the associated hypomagnesæmia.

A later trace, with potassium of 2.0 mEq/L, is shown below. The U waves are now separate, but not particularly striking. ECG is a poor tool here and there is no substitute for actual electrolyte measurements.

Gitelman’s is a variant of Bartter’s syndrome12.

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