Bone Abstracts

Bone metabolism disorders and hypercalcemia occur often in kidney transplant recipients.

In 59 kidney recipients (aged 22–74 years, creatinine clearance > 50 ml/min) who were hypercalcemic on more than three consecutive previous visits, the following serum parameters were estimated 1–147 months posttransplant: iPTH, Ca total and ionized, Pi, total and bone alkaline phosphatase, crosslaps, 25(OH)D3, cyclosporine/tacrolimus trough levels. Urine creatinine and Ca were also measured, and creatinine clearance and Ca:creatinine clearance ratios were estimated. According to the Ca:CrCl ratio patients were divided into three groups; i) < 0.01, probably impaired sensitivity of calcium-sensing receptors, ii) 0.01-0.02, normal range iii) >0.02, usually found in hyperparathyroidism. After blood sampling, ECG was performed and QTc interval estimated. None of the patients received medications known to prolong the QT interval (i.e., amiodarone). Results (median with range): Ca total 2.76, 2.54–3.27 (reference range 2.14–2.53 mmol/l), Ca ionized 1.40, 1.33–1.69 (reference range 1.18–1.32 mmol/l), iPTH 14.2, 5.1–97.6 (reference range1.0–6.0 pmol/l), QTc 0.393, 0.347-0.443, below the reference range in one patient (reference range 0.35–0.45 s). No significant correlation between the QTc interval length and total and ionized calcium, Pi, bone turnover parameters and 25(OH)D3 levels was found. The QTc interval length did not differ significantly among groups of patients according to Ca:creatinine clearance ratios. In patients with Ca:creatinine clearance ratios > 0.02 (n=24) QTc interval length correlated significantly negatively with cyclosporine A trough levels.

Conclusions: In hypercalcemic kidney recipients, QTc intervals were not shortened and no relationship to calcium metabolism disturbances was found. Cyclosporine A might have an impact on the QTc interval.