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Cardiac conduction in patients with hypercalcaemia due to primary hyperparathyroidism
M Rosenqvist1, J Nordenström, M Andersson
1Department of Cardiology, Karolinska Institute, Karolinska Hospital, Stockholm, Sweden.
Objective:
To assess whether hypercalcaemia due to primary hyperparathyroidism is associated with significant cardiac arrhythmias.
Design And Participants:
The prevalence of cardiac arrhythmias and conduction disturbances was evaluated by 12-lead ECG and 24-hour long-term ECG during pre-surgical hypercalcaemia and after post-surgical normalization of serum calcium values in 20 patients with primary hyperparathyroidism.
Results:
After surgery, mean +/- SD calcium levels decreased from 2.85 +/- 0.1 to 2.40 +/- 0.1 mmol/l (P < 0.001). There was a significant increase in QT-intervals (0.36 +/- 0.05 vs 0.39 +/- 0.05) and QTc-intervals (0.38 +/- 0.04 vs 0.42 +/- 0.03) after surgery (P < 0.01). Long-term ECG showed no change in the minimal heart rate 47 +/- 8 vs 48 +/- 7 beats/min or in the longest RR interval 1.6 +/- 0.5 vs 1.6 +/- 0.5 s (P NS). There was no difference in the prevalence of supraventricular or ventricular arrhythmias. No episode of high-grade AV-block was observed before surgery. Circadian heart rate rhythm did not change between investigations.
Conclusions:
It is concluded that moderate hypercalcaemia, in spite of causing a shortening of the repolarization phase (QT-interval), has no clinically significant effect on cardiac conduction.