Preexisting Venous Calcification Prior to Dialysis Vascular Access Surgery
ABSTRACT Vascular calcification is present in arterial vessels used for dialysis vascular access creation prior to surgical creation. Calcification in the veins used to create a new vascular access has not previously been documented. The objective of this study was to describe the prevalence of venous calcification in samples collected at the time of vascular access creation. Sixty-seven vein samples were studied. A von Kossa stain was performed to quantify calcification. A semi-quantitative scoring system from 0 to 4+ was used to quantify the percentage positive area for calcification as a fraction of total area (0: 0; 1+: 1-10%; 2+: 11-25%; 3+: 26-50%; 4+: >50% positive). Twenty-two of 67 (33%) samples showed evidence of venous calcification. Histologic examination showed varying degrees of calcification within each cell layer. Among the subset of patients with calcification, 4/22 (18%), 19/22 (86%), 22/22 (100%), and 7/22 (32%) had calcification present within the endothelium, intima, media, and adventitia, respectively. The mean semi-quantitative scores of the 22 samples with calcification were 0.18 ± 0.08, 1.2 ± 0.14, 1.6 ± 0.13, and 0.36 ± 0.12 for the endothelium, intima, media, and adventitia, respectively. Our results demonstrate that vascular calcification is present within veins used to create new dialysis vascular access, and located predominately within the neointimal and medial layers.
[Show abstract] [Hide abstract]
ABSTRACT: The osteocyte-derived sclerostin has been shown to play a key inhibitor role in determining the normal extent of bone formation, and it consequently protects against the deleterious effects of uncontrolled bone growth. Sclerostin has been demonstrated to be upregulated during vascular smooth muscle cell calcification in vitro and has recently been identified in the human aorta at the protein level. Whether the effects of sclerostin on bone turnover and its vascular expression also translate into clinically significant changes in arteriovenous fistula patency is unknown. The primary outcome was loss of unassisted arteriovenous fistula patency, defined as arteriovenous fistula thrombosis or need for intervention. In this prospective cohort study, 350 prevalent hemodialysis patients were followed up for 12 months. Serum sclerostin levels were measured and arteriovenous fistula calcification was detected using a 64-detector computerized tomographic scanner. Patients with calcified arteriovenous fistula had higher serum sclerostin levels than patients without. Overall, 26 % of the patients reached the outcome during the follow-up. The 12-month arteriovenous fistula survival was reduced in patients with calcified arteriovenous fistulas. Patients with serum sclerostin levels above median levels at the start of the observation period had a worse arteriovenous fistula survival. Multivariable-adjusted Cox regression analyses revealed that only presence of arteriovenous fistula calcification and serum C-reactive protein level independently predicted loss of unassisted arteriovenous fistula patency. Our study suggests that the detection of arteriovenous fistula calcification and serum C-reactive protein levels might be useful for identifying patients at an increased risk for loss of unassisted arteriovenous fistula patency.Herz 10/2013; DOI:10.1007/s00059-013-3992-y · 0.78 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: Guidance varies regarding the optimal timing of arteriovenous fistula (AVF) creation. The aim of this study was to evaluate the association between uraemia, haemodialysis and early AVF failure. Immunoblotting and cell proliferation assays were performed on vascular smooth muscle cells (VSM) cells isolated from long saphenous vein samples to evaluate the cells' ability to proliferate when stimulated with uraemic (post-dialysis) and hyperuraemic (pre-dialysis) serum. Clinical data was collected prospectively for 569 consecutive radiocephalic (RCF) and brachiocephalic (BCF) fistulae. The primary outcome was AVF failure at 6 weeks. Dialysis status (haemodialysis (HD); pre-dialysis (Pre-D)), eGFR and serum urea were evaluated to determine if they affected early AVF failure. Human VSM cells demonstrated increased capacity to proliferate when stimulated with hyperuraemic serum. There was no significant difference in early failure rate of either RCF or BCF depending on dialysis status (pre-D RCF 31.4% (n = 188); pre-D BCF 22.4% (n = 165); HD RCF 29.3% (n = 99); HD BCF 25.9% (n = 116); p = 0.34). There was no difference in mean eGFR between those patients with early AVF failure and those without (11.2+/-0.2 ml/min/1.73 m2 vs. 11.6+/-0.4 ml/min/1.73 m2; p = 0.47). Uraemia was associated with early AVF failure (serum urea: 35.0+/-0.7 mg/dl vs. 26.6+/-0.3 mg/dl (p < 0.001)). We present the first in vivo evidence of an association between adverse early AVF outcomes and uraemia. This is supported mechanistically by in vitro work demonstrating a pro-mitogenic effect of hyperuraemic serum. We hypothesise that uraemia-driven upregulation of VSM cell proliferation at the site of surgical insult in contributes to higher early AVF failure rates.BMC Nephrology 01/2014; 15(1):179. DOI:10.1186/1471-2369-15-179 · 1.52 Impact Factor
Clinical Journal of the American Society of Nephrology 12/2013; 8(12):2183-5. DOI:10.2215/CJN.03650413 · 5.07 Impact Factor