Hypocalcæmia

Report:

Sinus rhythm

Borderline first degree AV block

PR 0.22”

Prolonged QT interval

QT 0.44”, QTc 0.50”

Comment:

The long QT is easy to spot because the T waves are relatively prominent from hyperkalæmia. The trace is fairly typical of renal failure patients. Some of them develop this appearance after parathyroidectomy for tertiary hyperparathyroidism, as in the example below, a 31 year old woman(Fig 156a). Her preoperative trace is shown in Fig Fig 156b, for comparison.

The importance of this pattern is that it seems to feature prominently in multiple choice exams. Recognition of hypocalcæmia remains important for other reasons110.

In hypocalcæmia, the ST segment is prolonged but the T wave itself remains relatively normal. This is probably the reason that ventricular arrhythmias of torsade de pointe type are exceedingly rare111.

For practical purposes, the QT interval can be judged prolonged if the T wave encroaches on the second half of the R-R interval.

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