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This Article Full Text (PDF) All Versions of this Article: 89/1/436    most recent ajcn.2008.26770v1 Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Fourtounas, C. Articles by Vlachojannis, J. G Search for Related Content PubMed PubMed Citation Articles by Fourtounas, C. Articles by Vlachojannis, J. G Agricola Articles by Fourtounas, C. Articles by Vlachojannis, J. G

Serum 25-hydroxyvitamin D status and cardiovascular outcomes in chronic peritoneal dialysis patients

Department of Internal Medicine–Nephrology, University of Patras, Patras University Hospital, Rio Patras 265 00, Greece, E-mail: cfourt{at}usa.net

Dear Sir:

We greatly appreciate the article of Wang et al (1), which is indeed the first and largest prospective study on serum 25-hydroxyvitamin D [25(OH)D] status and cardiovascular outcomes in peritoneal dialysis (PD) patients. The authors prospectively studied a cohort of 230 prevalent PD patients for 3 y and reported that low serum 25(OH)D concentrations were associated with an increased risk of cardiovascular events. However, this association was lost when controlling for residual renal function (RRF) and echocardiographic measures of cardiac hypertrophy and dysfunction. It is also noteworthy that nearly 60% of the cardiovascular events were due to circulatory congestion and 25(OH)D deficiency was more common in PD patients who had experienced loss of RRF.

Cardiovascular disease is the leading cause of death is patients with end-stage renal disease (2). Fluid and salt removal depends on RRF and ultrafiltration by PD (3). Although earlier studies reported excellent short-term blood pressure and volume control with PD, after 2–3 y of therapy and especially when RRF was lost, patients presented signs of volume overload and hypertension (4). The authors provide data that prevalent PD patients (mean PD duration was 26 mo) received an adequate PD dose for solute removal, as shown by measurement of their weekly urea clearance (Kt/V) and creatinine clearance, but do not mention other clinical parameters that may imply volume status, such as daily ultrafiltrate, or need for hypertonic (glucose: 3.86%) PD solutions.

Another issue is that the mean value of initial intact parathyroid hormone (PTH) was rather low in the study population. This might be the result of active vitamin D analog therapy in some patients, diabetic status, or the concentration of calcium in the lactate-buffered solutions used in PD, because a calcium dialysate concentration of 1.75 mmol/L is frequently related with low serum PTH levels, especially when combined with calcium-containing phosphate binders (5). The authors do not provide data regarding these issues or the exact indications for vitamin D analog administration in 37% of the study population.

The most interesting finding of Wang et al's study is that serum 25(OH)D concentrations had a different influence on cardiovascular outcomes in a special cohort of PD patients with well-preserved left ventricular systolic function and less severe left ventricular hypertrophy, even when adjusted for various parameters (including RRF). On the other hand, as expected, serum 25(OH)D concentrations had no impact on outcomes in PD patients with significant cardiovascular morbidity (1). If these results can be reproduced by prospective studies that also use PD patients’ volume status indices as a confounder, this might provide further evidence for more extensive use of vitamin D analogs in patients receiving PD, regardless of their indications for renal osteodystrophy, and complete the puzzle of the truth about the still unclear effect of vitamin D on mortality in dialysis patients (6).

ACKNOWLEDGMENTS

The authors had no conflict of interest to disclose.

REFERENCES

1. Wang, AYM, Lam, CWK, Sanderson, JE, et al.. Serum 25-hydroxyvitamin D status and cardiovascular outcomes in chronic peritoneal dialysis patients: a 3-y prospective cohort study. Am J Clin Nutr 2008;87:1631–8..[Medline]
2. Foley, RN, Parfrey, PS & Sarnak, MJ. The clinical epidemiology of cardiovascular disease in chronic renal disease. Am J Kidney Dis 1998;32(suppl_3):S112–9..[Medline]
3. Ates, K, Nergizoglu, G, Keven, K, et al.. Effect of fluid and sodium removal on mortality in peritoneal dialysis patients. Kidney Int 2001;60:767–76..[Medline]
4. Khandelwal, M, Kothari, J, Krishnan, M, et al.. Volume expansion and sodium balance in peritoneal dialysis patients. Part II: newer insights in management. Adv Perit Dial 2003;19:44–52..[Medline]
5. Moe, SM. Management of renal osteodystrophy in peritoneal dialysis patients. Perit Dial Int 2004;24:209–16..[Abstract/Free Full Text]
6. Al-Aly, Z. Vitamin D as a novel nontraditional risk factor for mortality in hemodialysis patients: the need for randomized trials. Kidney Int 2007;72:909–11..[Medline]

This Article Full Text (PDF) All Versions of this Article: 89/1/436    most recent ajcn.2008.26770v1 Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Fourtounas, C. Articles by Vlachojannis, J. G Search for Related Content PubMed PubMed Citation Articles by Fourtounas, C. Articles by Vlachojannis, J. G Agricola Articles by Fourtounas, C. Articles by Vlachojannis, J. G