Long QT, alteration of calcium-phosphate product, prevalence of ventricular arrhythmias and sudden death in peritoneal dialysis patients: a Holter study

Materials and methods We studied 79 patients on peritoneal dialysis. Each underwent 24-h electrocardiography (Holter monitoring) and measurement of the rate-corrected QT interval (QTc). We analyzed the correlation between QTc and plasma levels of Ca++, PO4, K+, Na+, Mg++, and parathyroid hormone (PTH). Results The mean QTc was 0.445 ± 0.04 s. In 55 patients, the QTc was prolonged (> 0.45 s). Mean laboratory values for the group were: PTH 344 ± 25 pg/mL, Ca++ 9.27 ± 0.11 mg/dL, PO4 5.5 ± 1.5 mg/dL, Na+ 139.6 ± 3.4 mmol/L, K+ 4.04 ± 0.64 mmol/L, and Mg++ 2.52 ± 0.43 mg/dL. Holter monitoring revealed complex premature ventricular contractions in 44 patients, monomorphic premature ventricular contractions in 16, and nonsustained ventricular tachycardia (NSVT) in 10. The QTc was significantly correlated with plasma levels of PO4 (r = 0.045, p < 0.05), PTH (r = 0.077, p < 0.02), and Ca++ (r = 0.076, p < 0.02). Eleven patients had Lown class 4a or 4b ventricular arrhythmias, and their mean QTc was 465 ± 0.02 ms. Ten had NSVT and their QTc was 464 ± 0.03 ms. Eleven patients died suddenly (mean QTc 465 ± 0.03 ms); all 11 had either NSTV or Lown class 4 ventricular arrhythmias. Conclusions Long QTc seems to be associated with an increased prevalence of ventricular arrhythmias that may be the cause of sudden cardiac death.