Changes in the ECG caused by electrolyte changes in primary hyperparathyroidism

The development of cardiac arrhythmias in a case of primary hyperparathyreoidism is described. The arrythmias (sino-auricular block and ventricular ectopic beats) were observed preoperatively in the presence of a raised serum calcium. Postoperatively with a fall of serum calcium to subnormal values the arrhythmias ceased while serum magnesium was very low. The electrophysiological basis of these findings is discussed and the importance of serum calcium- and magnesium estimation in cases of unexplained arrhythmias is stressed.