Hypercalcæmia

Report:

Sinus tachycardia 113/min

Borderline left ventricular hypertrophy voltage

Short QT interval consistent with hypercalcæmia

QT = 0.28” QTc = 0.34”

Comment:

The ECG is not a very good guide to the degree of hypercalcæmia; this is hardly surprising in view of the multiplicity of factors determining the QT interval. In addition, finding the precise end of the T wave (i.e., QT interval) is not a simple matter! This patient’s calcium rose to 4.74 mEq/L during treatment with calcitonin, saline and steroids, while the urine output reached 60 litres in a 24-hour period! The mandatory fluid loading without proper control of hypercalcæmia made the patient analogous to Baron Münchhausen’s horse after the battle (Fig 207a) below). Eventually, hypercalcæmia was controlled with mithramycin and she did well (Fig 207b).

The QT interval is measured from the onset of the QRS complex to the end of the T wave; it is usually corrected (QTc) for heart rate using the Bazett's formula:

QTc = (in seconds)

The problems relating to QT measurement have been summarised by Spodick149. Marriott advises using the Q-aT interval in hypercalcæmia150.

207a. 207b. Normalised ECG a day later, with T waves suggesting an inadvertent, but understandable volume overload.

208. 7 year old boy investigated for an innocent systolic murmur