Increased risk of cardiac death in primary hyperparathyroidism: What is a role of electrical instability?

Background: Increased risk of death in patients with primary hyperparathyroidism (PHPT) is referred to cardiovascular complications induced by hypercalcemia. At the moment the role of bioelectrical risk and of enhanced sympathetic activity, not related to cardiovascular complications, is unknown in PHPT patients. Methods: The study was designed to evaluate the QT parameters and sympathovagal balance in 28 PHPT uncomplicated patients compared to 29 healthy subjects (HS). Nine of 28 patients were restudied after parathyroidectomy. Standard ECG, short and 24-h ECG monitoring were performed to calculate QT parameters and Heart Rate Variability (HRV). Results: QTc interval resulted shorter in PHPT patients than in HS and QTc dispersion resulted higher in PHPT patients than HS. The physiological adaptation of QT length to R-R interval was lacking in PHPT patients. Enhanced sympathetic tone was found in PTHP patients than controls. These data were confirmed after parathyroidectomy. Conclusion: Our findings revealed an increased risk to develop life-threatening arrhythmias in PHPT patients due to bioelectrical instability induced by hypercalcemia. Parathyroidectomy doesn't seem to reverse this abnormality. (C) 2006 Elsevier Ireland Ltd. All rights reserved.