P1168ABDOMINAL AORTIC CALCIFICATION SCORE MODIFIES THE PROGNOSTIC VALUE OF SERUM MAGNESIUM LEVELS ON ALL CAUSE MORTALITY IN PERITONEAL DIALYSIS PATIENTS

Abstract

Abstract Background and Aims Low serum Mg (s-Mg) concentration has been associated with an increased risk of death in both the general and dialysis populations. In peritoneal dialysis (PD) patients, an inverse correlation between s-Mg and abdominal aortic calcification (AAC), estimated by plain lateral lumbar x-rays, as Leena Kauppila (LK) score (range 0-24), is well documented. LK score of 0-4 has been associated with the best event free survival (CORD study CJASN 2011). Here, we explored the possibility whether AAC could modify the relationship between s-Mg and all-cause mortality in PD patients. Method We studied 95 stable PD patients, 51 men 44 women, with a mean age of 63 ±14 years. The degree of AAC was evaluated with on plain lateral abdominal radiographs, as LK score. After completion of baseline assessment, including s-Mg measurements, patients were followed up for all-cause mortality. Results The mean of s-Mg and AAC in the whole group were 2.25±0.47 mg/dl and 6.65 ± 5.94 respectively. There was an strong inverse correlation (rho = -0.225; p=0.029) between s-Mg and AAC. During a median follow-up period of 23 months, 16 (17%) deaths occurred. There was a 78% reduction of all-cause mortality for every 1 mg/dl of increase in s-Mg {crude HR: 0.22 (95% CI, 0.06 - 0.78)}. An interacting effect between s-Mg and AAC was significant (p=0.005) after controlling for main effects. Then, the association between s-Mg and all-cause mortality by subgroups of AAC: higher tertile vs all lower, was examined (cut-offs of the tertiles for AAC were 3 and 9). In patients grouped in the lower tertiles, s-Mg was a significant predictor of all-cause mortality, even after adjustment for univariate significant predictors of all-cause mortality: age, cardiovascular disease, PD vintage and malnutrition-inflammation score (MIS) {adjusted HR: 0.14 (95% CI, 0.02-0.0.98)}. On the contrary, patients with AAC in the higher tertile of the baseline distribution, s-Mg levels were not predictive of outcome in either crude or the adjusted models. Conclusion The predictive value of s-Mg in all-cause mortality in PD patients appears to be critically dependent on AAC score. Thus, sustaining higher sMg levels, as by using higher Mg dialysate concentration, may have beneficial effects on clinical outcomes only in patients without AAC or at least in those with early lesion development.