Hypokalæmia: Long QTc or QU

Report:

Sinus rhythm 87/min

Diffuse ST/T changes

Long QT interval 0.48”

QTc 0.50”

Comment

It is practically impossible to tell QT from QU here. The patient was known, however, to have potassium 1.9 mEq/L, with normal calcium and magnesium. Accordingly, what we are looking at is a TU morphology, probably of the same significance as true QT prolongation33. Abnormalities improved but persisted day after potassium was normalised (23a).

In Fig 23b is another patient, a 34 year old alcoholic, with vomiting-induced hypokalæmia (2.0 mEq/L) and alkalosis. He in fact arrested in VF in Casualty. The reason for his prominent P waves is unknown; hypokalæmia, even marked, usually causes only a modest increase in P wave amplitude. His U waves were quite tall; at times hyperkalæmia is suspected by the uninitiated.

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