Risk of Corrected QT Interval Prolongation after Pamidronate Infusion in Children

Background: Hypocalcemia carries a risk of cardiac conduction incidents and death. Hypocalcemia is a frequent adverse effect of pamidronate. Objective: The objective of this study was to investigate whether pamidronate infusion lengthens the ventricular repolarization in children. Design and Methods: Thirty-four children with cerebral palsy and severe osteoporosis were treated for approximately 1 yr with pamidronate (three times per year). Calcemia and corrected QT interval (QTc) (in which the QT interval is a measure between the Q and T waves in the electrical cycle of the heart) were measured before and after each cycle of intravenous infusions. Results: Pamidronate decreased calcemia in all patients from 2.40 to 2.21 mM (P < 0.0001) and increased QTc from 390 to 403 ms (P < 0.0001), with 7.4% of postinfusion QTc becoming longer than 440 ms. QTc at baseline was significantly correlated to final QTc (P < 0.0001; r(2) = 0.27). Conclusions: Because we observed a lengthening in QTc after bisphosphonate infusion, we recommend that children treated with pamidronate should receive attention as to other possible risk factors of prolonged QT and have a preinfusion and postinfusion measurement of their QTc. (J Clin Endocrinol Metab 95: 3768-3770, 2010)