Digoxin, hypercalcaemia, and cardiac conduction

The cardiac effects of hypercalcaemia are usually manifest as a shortening of the QT-interval. Hypercalcaemia is infrequently associated with a clinic ally manifest arrhythmia. However, concomitant therapy with digoxin or unde rlying cardiac disease can potentiate the arrhythmogenic effects of hyperca lcaemia, leading to a symptomatic rhythm disorder. We describe a symptomati c arrhythmia, which developed in a patient with hypercalcaemia secondary to squamous cell carcinoma of the bronchus. The patient was on digoxin therap y at the time. The arrhythmia did not recur after discontinuation of digoxi n therapy and correction of the hypercalcaemia. Because of its effect on ca rdiac conduction, hypercalcaemia should be considered in the evaluation of any patient with an unexplained bradyarrhythmia. Conversely, patients with hypercalcaemia should discontinue digoxin therapy and be evaluated for the presence of rhythm disorders while receiving appropriate treatment for hype rcalcaemia.