The relationship between serum calcium and phosphate levels and cardiac valvular procedures in the hemodialysis population

Abstract

Background: Cardiac valvular disease is a common complication in hemodialysis patients, with a prevalence of up to 9%. In these patients, calcium-phosphate imbalance is associated with systemic and cardiac calcification. We investigated the relationship between abnormal calcium and phosphate levels and valvular disease sufficiently severe to require an invasive procedure. Methods: We analyzed data from 12,509 hemodialysis patients from the US Renal Data System database, 204 of whom underwent a valvular procedure. All were prevalent in-center dialysis patients as of 1993, when cross-sectional data were collected. Results: In a Cox multivariate model, a serum phosphate level of 5.0 mg/dL or greater (≥1.62 mmol/L) was associated with increased risk for a valvular procedure compared with a phosphate level less than 5 mg/dL (<1.62 mmol/L; hazard ratio, 1.47; P = 0.033). A calcium level less than 8.8 mg/dL (<2.2 mmol/L) was associated with fewer valvular procedures compared with a normal calcium level (hazard ratio, 0.61; P = 0.018). However, a high calcium level (>10.5 mg/dL [>2.63 mmol/L]) had no significant relationship with the outcome (hazard ratio, 0.89; P = 0.65) compared with a normal level. Calcium-phosphate product was not significant as an interaction term and therefore was not included in the final analysis. The relationship of parathyroid hormone (PTH) level to outcome was not significant. Conclusion: A serum phosphate level of 5.0 mg/dL or greater (≥1.62 mmol/L) is associated with increased risk for a valvular procedure, and a low calcium level is associated with fewer valvular procedures. There is no compelling evidence that elevated calcium or PTH levels have a significant relationship to valvular disease that results in an invasive procedure. Am J Kidney Dis 41:411-421.