title: Cardiac conduction in patients with hypercalcaemia due to primary hyperparathyroidism.
abstract: OBJECTIVE
  To assess whether hypercalcaemia due to primary hyperparathyroidism is associated with significant cardiac arrhythmias.
  
  
  METHODS
  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.
authors.affiliation: Department of Cardiology, Karolinska Institute, Karolinska Hospital, Stockholm, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Rosenqvist
authors.forename: J
authors.initials: J
authors.lastname: Nordenström
authors.forename: M
authors.initials: M
authors.lastname: Andersson
authors.forename: O K
authors.initials: OK
authors.lastname: Edhag
mesh_terms: D000328:Adult; D000368:Aged; D001145:Arrhythmias, Cardiac / Q000209:etiology*; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D006934:Hypercalcemia / Q000150:complications* / Q000209:etiology / Q000503:physiopathology; D006961:Hyperparathyroidism / Q000150:complications* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D016105:Parathyroidectomy; D011184:Postoperative Period