Hyperhomocysteinemia, anticardiolipin antibody status, and risk for vascular access thrombosis in hemodialysis patients

The Positive Association of Homocysteine (Hcy) with Arteriovenous Fistula Thrombosis (AVFT) in Chinese Patients on Hemodialysis: A Retrospective Cohort Study

BACKGROUND

Homocysteine (Hcy) is generally elevated in dialysis patients and is one of the independent risk factors for thrombosis. However, the relationship between Hcy level and the risk of arteriovenous fistula thrombosis (AVFT) has not yet fully been understood. Current evidence regarding this association is limited, particularly among Chinese populations. Given the significance of this relationship in health care and public health, further investigation is essential. This study aims to clarify the association between Hcy and AVFT. In addition, it seeks to examine the synergistic effects of Hcy alongside other factors influencing AVFT. It also intends to determine how Hcy interacts with variables such as diabetes and impacts the risk of AVFT.

METHODS

A retrospective cohort study was conducted involving 983 hemodialysis patients. Data on demographic characteristics, comorbidities, laboratory test indicators, and clinical symptoms were collected from all participants. Statistical analyses, including logistic regression, smooth curve fitting, and joint interaction effects analysis, were employed to address the research questions.

RESULTS

The overall prevalence of AVFT in the study population was 16.20%. A significant association between Hcy levels and the risk of AVFT was found (odds ratio [OR], 1.14; 95% confidence interval [CI], 1.11-1.16; P < 0.001). This association remained significant after adjusting for multiple variables (OR, 1.13; 95% CI, 1.11-1.17; P < 0.001). Participants were categorized into high and low Hcy groups based on the median (25.2 μmol/L), with a significantly elevated risk of AVFT was observed in the high Hcy group compared to the low Hcy group (OR, 5.55; 95% CI, 3.59-8.55; P < 0.001). This risk remained significantly elevated after adjustment for covariates (OR, 3.59; 95% CI, 1.83-7.55, P < 0.001). Subsequent exploratory subgroup analyses revealed similar significant interactions (all P values for interaction >0.05). Furthermore, sensitivity analyses indicated that diabetes and Hcy levels exhibit a synergistic multiplicative and additive interaction in the risk of AVFT (both P < 0.05).

CONCLUSION

The findings suggest that elevated Hcy levels are linked to an increased risk of AVFT. The data highlight diabetes as a synergistic interaction factor through which Hcy influences AVFT risk. These results underscore the necessity for further research, especially considering potential confounding factors. Future studies should aim to confirm these findings and explore the underlying mechanisms of the observed associations.

Distal Forearm Arteriovenous Fistula Maturation in Diabetic Hemodialysis Patients

PURPOSE

Atherosclerotic disease of the forearm arteries can impede the maturation of distal fistulas in diabetic patients. The goal of this study was to look at the maturity of diabetic hemodialysis patients' distal forearm (radiocephalic snuffbox or distal forearm) arteriovenous fistulas.

MATERIALS AND METHODS

Patients with chronic renal failure who were candidates for distal forearm radiocephalic arteriovenous fistula implantation were evaluated in this cross-sectional study. Patients' demographic details, underlying disorders, laboratory measurements, vital signs, and information on their surgery were all noted. Patients were checked for fistula development 1 week, 1 month, 2 months, and then monthly until 6 months after surgery. Arteriovenous fistula maturation characterized by optimal blood flow, vessel dilation, and structural adaptations.

RESULTS

Among 343 patients (56% male, 44% female, mean age: 57.32 ± 12.48 years), hypertension prevailed (81.9%), followed by hyperlipidemia (42.3%) and coronary artery disease history (25.9%). AVFs achieved 58.3% maturation in 64.98 ± 11.05 days; higher BP during creation correlated with successful maturation (17.02 ± 1.46 mmHg vs 13.90 ± 1.93 mmHg, P < .05). No significant statistical difference found in distal forearm arteriovenous fistula maturation between males (57.8%) and females (58.9%) (P > .005). However, 41.7% of AVFs failed in 18.83 ± 17.89 days. Failed AVFs exhibited lower BP during operation and failure (11.75 ± 1.86 mmHg). Kaplan-Meier analysis depicted maturation probabilities over 90 days post-surgery.

CONCLUSION

Diabetes and patient sex did not affect the maturation time of distal forearm AVFs in hemodialysis patients. Increased blood pressure during and after surgery correlated with shorter maturation time.

Antiphospholipid Antibodies Associated with Native Arteriovenous Fistula Complications in Hemodialysis Patients: A Comprehensive Review of the Literature

Antiphospholipid antibody (aPL)-persistent positivity is frequent in hemodialysis (HD) patients. Native arteriovenous fistula (AVF) complications such as stenosis and thrombosis are among the most important causes of morbidity and mortality in hemodialysis patients. The association between aPL positivity and AVF thrombosis seems to now be well established. However, whether aPL positivity is associated with other AVF complications, such as maturation failure or stenosis, is not well known. Given the significant impact of AVF failure on patient's prognosis, it is of interest to further investigate this particular point in order to improve prevention, surveillance and treatment, and, ultimately, the patient's outcome. This literature review aims to report the recent literature on aPL-associated native AVF complications.

A meta-analysis of the association between diabetic patients and AVF failure in dialysis

PURPOSE

The most preferable vascular access for patients with end-stage renal failure needing hemodialysis is native arteriovenous fistula (AVF) on account of its access longevity, patient morbidity, hospitalization costs, lower risks of infection and fewer incidence of thrombotic complications. Meanwhile, according to National Kidney Foundation (NKF)̸Dialysis Out-comes Quality Initiative (DOQI) guidelines, AVF is more used than before. However, a significant percentage of AVF fails to support dialysis therapy due to lack of adequate maturity. Among all factors, the presence of diabetes mellitus was shown to be one of the risk factors for the development of vascular access failure by some authors. Therefore, this review evaluates the current evidence concerning the correlation of diabetes and AVF failure.

METHODS

A search was conducted using MEDLINE, SCIENCE DIRECT, SPRINGER, WILEY-BLACKWELL, KARGER, EMbase, CNKI and WanFang Data from the establishment time of databases to January 2016. The analysis involved studies that contained subgroups of diabetic patients and compared their outcomes with those of non-diabetic adults. In total, 23 articles were retrieved and included in the review.

RESULTS

The meta-analysis revealed a statistically significantly higher rate of AVF failure in diabetic patients compared with non-diabetic patients (OR = 1.682; 95% CI, 1.429-1.981, Test of OR = 1: z = 6.25, p <.001).

CONCLUSIONS

This review found an increased risk of AVF failure in diabetes patients. If confirmed by further prospective studies, preventive measure should be considered when planning AVF in diabetic patients.

Thrombophilia Associated with Early Post-angioplasty Thrombosis of Dialysis Vascular Access

AIM

Percutaneous transluminal angioplasty (PTA) is widely used as the primary treatment for dialysis vascular access dysfunction. Nonetheless, many patients develop early occlusion after angioplasty. Thus, we investigated the role of thrombophilia in access occlusion within 30 days of angioplasty.

MATERIALS AND METHODS

This case-control study included patients who underwent PTA for dialysis vascular access dysfunction. Patients who experienced occlusion within 30 days of angioplasty were included in the case group and those without occlusion for at least 30 days after angioplasty were included in the control group. All patients were tested for protein C, protein S, antithrombin III, lupus anticoagulant, and anticardiolipin antibodies.

RESULTS

From February to October 2015, 462 patients underwent PTA for dialysis vascular access dysfunction. Forty-one patients (8.9%) had early occlusion within 30 days of angioplasty. The case group had more graft accesses (73 vs. 31%, P < 0.001) and thrombotic occlusions (67 vs. 15%, P < 0.001). A higher incidence of protein C (10 vs. 2%), protein S (15 vs. 5%), and antithrombin III (10 vs. 2%) deficiency and elevated anticardiolipin antibody (22 vs. 10%) levels were observed in the case group. Overall, 26 patients (63%) in the case group had at least one thrombophilic factor, compared with 15 patients (37%) in the control group (unadjusted odds ratio [OR], 3.004; 95% confidence interval [CI], 1.223-7.380; P = 0.027). After adjustment for confounding factors, the association between thrombophilic factors and early occlusion remained (adjusted OR, 3.806; 95% CI, 1.018-14.220; P = 0.047).

CONCLUSION

Thrombophilia is associated with early occlusion after angioplasty for hemodialysis vascular access.

Risk of Vascular access Thrombosis in Patients with Systemic Lupus Erythematosus on Hemodialysis

Introduction

Anticardiolipin antibody is associated with increased risk of vascular access thrombosis (VAT) in hemodialysis (HD) patients. Systemic lupus erythematous (SLE) patients have a high prevalence of anticardiolipin antibodies, but it is not clear whether these patients are at high risk of developing vascular access thrombosis.

Methods

Thirty six SLE patients on HD, who had either an arterio-venous (AV) graft or AV fistula as vascular access, and were not on anticoagulation treatment, were retrospectively identified at Henry Ford Hospital. A similar number of patients without SLE, matched for age, sex, race and type of vascular access were selected as a control population. Vascular access thrombosis rate at one year was compared between two groups.

Results

Mean age at dialysis was 36±10 years in 36 SLE patients (28 females, 8 males) and was 38±6.4 years in 36 non-SLE patients (29 females, 7 males). Of all patients, 29/36 (80.5%) SLE and 27/36 (75%) non-SLE patients had AV grafts, whereas the rest had AV fistulas as vascular access (19.5% SLE and 25% non-SLE patients). Out of 36 SLE patients, 24 (66.6%) patients developed VAT at one year as compared to 14 (38.9%) patients in non-SLE group (p<0.05). The odds ratio of VAT in SLE patients was 3.1 (95% CI 1.2–8.2).

Conclusion

SLE patients on hemodialysis are more likely to develop vascular access thrombosis as compared to non-SLE patients.

Hemodialysis Arteriovenous Fistulas: A Nineteenth Century View of a Twenty First Century Problem

This is a literature review which approaches the problem of successful use of arteriovenous fistulas for dialysis within the construct of Virchow's triad. By organizing the literature with regard to Virchow's concepts of blood flow, vascular injury, and thrombophilia an improved understanding arteriovenous fistula placement, maintenance and repair can be obtained. This process is designed to increase understanding and options for treatment by looking at this problem and using scientific knowledge gained in cardiology, oncology and vascular surgery medicine. Future approaches to fistulas will hopefully be a multifaceted and based in cellular pathophysiology as well as surgical and radiologic interventions and repairs.

Coagulation, thrombophilia and patency of arteriovenous fistula in children undergoing haemodialysis compared with healthy volunteers: a prospective analysis

This study aimed to assess whether markers of coagulation, fibrinolysis or thrombophilia are increased in children on haemodialysis compared with controls and whether measurement of any of these factors could help to identify patients at an increased risk of arteriovenous fistula (AVF) occlusion. Blood samples were taken from 55 children immediately before a session of haemodialysis and from 20 healthy volunteers. Thrombin-antithrombin (TAT), D-dimer, plasmin-antiplasmin (PAP) and anticardiolipin immunoglobulin G (ACA-Ig G) were measured by ELISA. Factor V Leiden mutation (G1691A) was determined by gene polymorphism [restriction fragment length polymorphism (RFLP)]. Determination of the patency of the AVF was prospectively followed up for a minimum of 4 years or until the AVF was nonfunctioning. Fifty-five patients were studied with a median follow-up of 659 days (range 30-1670 days). A significant increase was found in the levels of D-dimer, PAP and ACA-Ig G in haemodialysis patients with thrombosed and nonthrombosed native AVFs vs.

CONTROLS

There was a significant difference between both chronic haemodialysis patients with thrombosed and nonthrombosed native AVF with regard to ACA-IgG levels. At 1 year follow-up, primary patency was 61.4% (27 patients). In multivariate analysis, D-dimer was inversely associated with secondary patency.Thrombophilia may predispose children with end stage renal disease to access failure. The promising finding is that in children on haemodialysis, D-dimer levels were increased and inversely correlated with secondary patency. Further evaluation is required into the possible role of D-dimer as a biomarker of AVF occlusion.

[Antiphospholipid syndrome in nephrology. Kidney damage and practical aspects of the management]

The antiphospholipid syndrome is a thrombophilia characterized by the combination of arterial and/or venous thrombotic events or obstetric clinical events, associated with persistent presence of antiphospholipid antibodies. In this syndrome, thromboses may affect all of the vascular tree, renal damage is frequently associated with a specific antiphospholipid syndrome nephropathy. We propose in this review to provide updated recommendations on the management of antiphospholipid syndrome in nephrology. Treatment is based on long-term anticoagulant therapy with or without antiplatelet agents according to clinical events. The use of a conventional nephroprotection must not be forgotten (strict control of blood pressure with drugs blocking the renin-angiotensin-aldosterone system). Catastrophic antiphospholipid syndrome is an extremely severe complication which can threaten the vital prognosis of the patient. This justifies particular surveillance, as well as prevention in high-risk situations. We also illustrate the difficulties of long-term management in these patients, both in dialysis or kidney transplantation.

Hyperhomocysteinemia and vascular access thrombosis in hemodialysis patients: a retrospective study

BACKGROUND

Elevated total plasma homocysteine is an independent risk factor for arterial and venous thrombosis in patients with normal renal function. Patients on hemodialysis have a high prevalence of mild to moderate hyperhomocysteinemia. Conflicting retrospective analyses and prospective studies have been reported regarding the association between total homocysteine levels and hemodialysis vascular thrombosis. The purpose of this retrospective study was to investigate the relationship between hyperhomocysteinemia and vascular access thrombosis (VAT) in patients on hemodialysis.

METHODS

One hundred and twenty-five patients undergoing dialysis were selected as subjects. The experimental group participants were identified as those having one or more VAT during the previous 13 months and the control group participants had no access thrombosis during the same period. Additional subgroup analysis included the presence of hypertension, diabetes, low-density lipoprotein levels, sex, and use of aspirin.

RESULTS

No statistically significant difference was found in total homocysteine levels between the two groups (P = 0.27). No association was found between VAT and sex (P = 0.09), VAT and hypertension (P = 0.96), VAT and diabetes (P = 0.49), nor VAT and low-density lipoprotein level (P = 0.04). A lower rate of VAT was associated with aspirin intake (P = 0.04).

CONCLUSION

This study did not demonstrate a relationship between total homocysteine concentrations and risk of VAT in patients with end-stage renal disease on hemodialysis. There were no significant differences in the number of VAT across additional variables of sex and previous morbidity. Aspirin intake was associated with a lower incidence of VAT.

Thrombophilia and arteriovenous fistula survival in ESRD

BACKGROUND AND OBJECTIVES

The role of thrombophilia in failing arteriovenous fistula (AVF) among patients with ESRD undergoing hemodialysis is not established. This study aimed to assess whether AVF primary patency is associated with thrombophilia and coagulation abnormalities.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This observational study screened 219 patients between 2002 and 2004 for thrombophilia before AVF surgery. Thrombophilia included factor V Leiden and prothrombin G20210A mutations, protein C and antithrombin activities, and protein S. Coagulation abnormalities included high factor VIII:C, homocysteine, fibrinogen, and d-dimer levels; presence of antiphospholipid antibodies; and short thrombin time. We reviewed patient charts for comorbid conditions, AVF maturation and interventions, kidney transplantation, and patient survival (mean follow-up duration, 3.6 [range, 2.3-5.8] years). Primary patency from the AVF placement and functional primary patency from the first AVF cannulation were analyzed with Kaplan-Meier and Cox proportional hazards models.

RESULTS

Thrombophilia was present in 9% of the patients, and coagulation abnormalities occurred in 77%. One-year primary patency was 68%; 46% of the AVF failures occurred before the initiation of hemodialysis. Female sex (hazard ratio [HR], 2.6; 95% confidence interval [CI], 1.7-4.1) and thrombophilia (HR, 2.2; 95% CI, 1.2-4.2) were independent risk factors for loss of primary patency. Thrombophilia mutations or low antithrombin level (HR, 3.8), female sex (HR, 2.5), and diabetes (HR, 1.9) were associated with shortened functional primary patency of AVF.

CONCLUSIONS

Against the background of frequent coagulation abnormalities, thrombophilia and female sex predispose patients with ESRD to access failure, mostly due to thrombosis or stenosis.

Severe vascular lesions and poor functional outcome in kidney transplant recipients with lupus anticoagulant antibodies

The impact of antiphospholipid antibodies (APA) on clinical outcome and graft histology following renal transplantation remains poorly known and controversial. We retrospectively explored the functional and histological significance of APA, primarily lupus anticoagulant (LA), in kidney transplant recipients using a systematic evaluation of 3- and 12-month posttransplant screening biopsies and glomerular filtration rate measurements (mGFR). During the study period, 37 patients had APA (2.7%), primarily LA, and 12 fulfilled antiphospholipid syndrome (APS) diagnostic criteria (0.8%) at the time of transplantation. Early after transplantation, 4 of the 12 APS patients died. Early thrombosis of graft vessels and deep venous thrombosis occurred more frequently in APA+ patients than in controls (27% vs. 7%, p < 0.05 and 35% vs. 14%, p < 0.05, respectively). The survival rate was significantly lower in patients with APS. Strikingly, the hallmark lesions of APS-associated nephropathy (APSN) were found in most of screening graft biopsies in APA+ patients but not in the controls. Accordingly, APA+ patients had a dramatic increase in chronic vascular scores and a faster decline in mGFR at 1 year. In conclusion, renal transplantation may be life-threatening in APS patients, and the presence of LA at the time of transplantation is associated with a high rate of allograft APSN and poor transplantation outcomes.

Hyperhomocystinemia and the Prevalence of Symptomatic Atherosclerotic Vascular Disease in Taiwanese Chronic Hemodialysis Patients: A Retrospective Study

AIM

Hyperhomocystinemia is now recognized as an independent risk factor for atherosclerotic cardiovascular disease in patients with normal renal function. Hyperhomocystinemia is common in patients with chronic renal failure. This aim of this study was designed to look for associations between hyperhomocystinemia and clinically symptomatic atherosclerotic vascular disease (ASVD) in Taiwanese chronic hemodialysis patients.

METHODS

Two hundred patients undergoing hemodialysis were enrolled in the study. They had predialysis blood work performed for total homocysteine, serum folate, and vitamin B12 levels. A history of clinically significant ASVD was elicited using information from the patients' questionnaires and verified by careful inpatient and outpatient chart review.

RESULTS

Mean homocysteine concentration was 29.0 micromol/L overall. A total of 196 patients had hyperhomocystinemia and were enrolled in this study. ASVD was present in 24.5% of patients. The mean homocysteine concentration was 31.9 micromol/L and 28.7 micromol/L in patients with (n = 48) and without (n = 148) ASVD, respectively (P = 0.04). There was association hyperhomocystinemia between chronic hemodialysis patients with ASVD and without ASVD. There were significant differences including age, homocysteine level, vitamin B12 level and glucose intolerance in the two groups (P < 0.05). Plasma homocysteine concentrations showed significant positive correlations with serum folate or vitamin B12 in majority patients. No patient had serum folate or vitamin B12 deficiency. The adjusted odds ratio for atherosclerotic disease was 2.8 (95% CI, 1.109-7.467) for those subjects with a homocysteine level in the highest quartile compared with the lowest 3 quartiles.

CONCLUSIONS

The prevalence of hyperhomocystinemia is 98% among hemodialysis patients. There is a significant association between hyperhomocystinemia and ASVD in Taiwanese chronic hemodialysis patients. There are also associations between homocysteine levels and serum folate/vitamin B12 levels in the majority of the patients. Clinical trials are needed to determine the optimal therapy of folic acid dose for hyperhomocystinemia in Taiwanese chronic hemodialysis patients in the future.

Prognostic factors influencing the patency of hemodialysis vascular access: literature review and novel therapeutic modality by far infrared therapy

In Taiwan, more than 85% of patients with end-stage renal disease undergo maintenance hemodialysis (HD). The native arteriovenous fistula (AVF) accounts for a prevalence of more than 80% of the vascular access in our patients. Some mechanical factors may affect the patency of hemodialysis vascular access, such as surgical skill, puncture technique and shear stress on the vascular endothelium. Several medical factors have also been identified to be associated with vascular access prognosis in HD patients, including stasis, hypercoagulability, endothelial cell injury, medications, red cell mass and genotype polymorphisms of transforming growth factor-beta1 and methylene tetrahydrofolate reductase. According to our previous study, AVF failure was associated with a longer dinucleotide (GT)n repeat (n > or = 30) in the promoter of the heme oxygenase-1 (HO-1) gene. Our recent study also demonstrated that far-infrared therapy, a noninvasive and convenient therapeutic modality, can improve access flow, inflammatory status and survival of the AVF in HD patients through both its thermal and non-thermal (endothelial-improving, anti-inflammatory, antiproliferative, antioxidative) effects by upregulating NF-E2-related factor-2-dependent HO-1 expression, leading to the inhibition of expression of E-selectin, vascular cell adhesion molecule-1, and intercellular adhesion molecule-1.

Local Activation of Interleukin 6 Signaling Is Associated With Arteriovenous Fistula Stenosis in Hemodialysis Patients

BACKGROUND

Vascular access failure is the main cause of morbidity in hemodialysis patients. Stenosis of the arteriovenous fistula (AVF) is similar histologically to atherosclerosis. Recent studies showed that interleukin 6 (IL-6) has a key role in the pathogenesis of atherosclerosis by binding 2 specific receptors, gp80 and gp130. When activated, gp130 interacts with a tyrosine kinase, Janus kinase (JAK2), which then activates a transcription factor, signal transducers and activators of transcription (STAT3), directly turning on several proinflammatory genes. The aim of this study is to evaluate gp130 expression and JAK2/STAT3 activation within stenotic AVFs.

METHODS

44 patients undergoing surgery for AVF creation were enrolled; 10 of them had AVF failure with histologically proven AVF stenosis (wall-lumen ratio > 1). A venous fragment of the AVFs was collected during creation and revision of the vascular access. gp130 and gp80 expression, as well as JAK/STAT activation, were evaluated by means of confocal microscopy. Peripheral-blood mononuclear cells were isolated at the time of AVF creation and revision.

RESULTS

gp130 protein expression, barely detectable in native AVFs, was strikingly increased within the venous branch of stenotic AVFs. The signaling subunit of the IL-6 receptor broadly colocalized with gp80, the IL-6-binding subunit. gp130-expressing cells were mainly CD34(+), suggesting that this receptor is expressed primarily by neovasculature endothelial cells. At the same time, a significant increase in phosphorylation of JAK2/STAT3 was observed in endothelial cells of stenotic AVFs. Interestingly, peripheral-blood mononuclear cells isolated at the time of AVF failure presented strikingly greater IL-6 expression compared with dialysis age-matched controls.

CONCLUSION

IL-6 receptor activation may have a role in the pathogenesis of AVF failure in hemodialysis patients and may represent a potential therapeutic target in this setting.

Gene polymorphism association studies in dialysis: vascular access

Complications of the vascular access site for hemodialysis are a major cause of morbidity, suboptimal dialysis, and hospitalization. Vascular access for dialysis that is achieved by central venous catheters is associated with complications such as infection and thrombosis. Arteriovenous fistulas and grafts are also at risk for infectious complications. Further, proliferation of the venous wall with secondary thrombosis is a common pathophysiological process that leads to vascular access dysfunction. Genetic polymorphisms that contribute to vascular access failure are found among factors of the coagulation cascade, and host mediators that induce endothelial dysfunction as well as vessel wall proliferation. The two most common mutations of coagulation factors seem to influence the risk of central venous catheter and fistula thrombosis. Indeed, both the single nucleotide polymorphism of the factor V gene at amino acid position 506 (factor V Leiden mutation) and the prothrombin 20210 polymorphism have been associated with thrombotic complications of the vascular access. Among the endothelium-directed factors, a polymorphism of the methylene tetrahydrofolate reductase gene coding for an enzyme that degrades the endothelium toxic product homocysteine, has been associated with fistula failure. While the angiotensin converting enzyme polymorphism does not seem to be associated with vascular access complications, polymorphisms of the profibrogenic cytokine transforming growth factor-beta1 are associated with the prognosis of native arteriovenous fistulae. The role of pro- and anti-inflammatory cytokine gene polymorphisms as prognostic factors for vascular access is yet to be clearly defined.

Vascular access thrombosis prophylaxis

Vascular access thrombosis in the hemodialysis patient leads to significant cost and morbidity. Fistula patency supersedes graft patency, therefore obtaining a mature functioning fistula in patients approaching end-stage renal disease (ESRD) by early patient education and referral needs to be practiced. Current methods to maintain vascular access patency rely on early detection and radiologic or surgical prevention of thrombosis. Study of thrombosis biology has elucidated other potential targets for the prophylaxis of vascular access thrombosis. The goal of this review is to examine the current available methods for vascular access thrombosis prophylaxis.

Anticardiolipin antibodies and vascular access thrombosis in Taiwanese haemodialysis patients with chronic hepatitis C: a retrospective study

Hepatitis C virus causes various extrahepatic immunologic abnormalities. Vascular access thrombosis (VAT) is a major cause of morbidity in chronic haemodialysis (HD) patients. Immunoglobulin-G anticardiolipin antibody (IgG-ACA) is strongly associated with venous and arterial thrombosis in patients with normal renal function. Previous investigations have reported the association of raised IgG-ACA titre recurrent with VAT in HD patient, and also few equivalent studies were reported the same in Taiwan. This study attempted to determine whether raised IgG-ACA titres are associated with increased risk of recurrent VAT in HD patients with chronic hepatitis C. This study enrolled 98 chronic hepatitis C patients undergoing HD. IgG-ACA titre and hepatitis C marker were measured for all subjects. Raised IgG-ACA titres were present in 29.6% (29/98) of patients. In both groups (raised and normal IgG-ACA), the type of shunt did not differ (p = 0.416). There was strong association between raised IgG-ACA titre and recurrent VAT (p = 0.0004). In predicting for more or one episodes of VAT using multiple logistic regression, synthetic graft (p < 0.0001), raised IgG-ACA titre (p = 0.039), presence of hepatitis B (p = 0.004) and haemodialysis duration (p = 0.039) were significant factors. The prevalence of raised IgG-ACA titres was 39.6% among chronic hepatitis C with HD patients. There was strong association between raised IgG-ACA titre and recurrent VAT, and this finding may be the consequence of pathogenetic role of raised IgG-ACA titres on the development of VAT status in HD patients with chronic hepatitis C.

Hyperhomocysteinaemia and vascular access thrombosis among chronic hemodialysis patients in Taiwan: a retrospective study

Vascular access thrombosis (VAT) is an important cause of morbidity for chronic haemodialysis (HD) patients. Some risk factors for VAT have been well-defined for chronic HD patients from western countries. However, only a few such factors have been confirmed for Taiwanese patients. This study attempted to determine the association between hyperhomocysteinaemia and the incidence of VAT for chronic HD patients in Taiwan. We retrospectively enrolled a total of 196 patients into this study during 2003. The patients were separated into VAT (n = 142) and control (n = 54) group. The participants of the VAT group were identified as those having one or more VAT, and the participants of the control group were those with no VAT in the past. The mean follow-up period was 48 months. The mean serum homocysteine levels were 29.5 +/- 9.6 and 29.1 +/- 9.5 micromol/l for the VAT (n = 142) and the control (n = 54) group, respectively. There was no significant difference in the level of homocysteine between the VAT and the control group (p = 0.70). Female chronic HD patients had significantly greater mean total homocysteine levels than male (30.89 micromol/l, 95% CI 28.84-32.94 vs. 28.06 micromol/l, 95% CI 26.32-29.82, respectively, p = 0.038). That synthetic graft was a significant risk factor for VAT was determined using multivariate logistic regression analysis. There was no association between serum total homocysteine levels and the incidence of VAT in chronic HD patients in Taiwan.

Hyperhomocysteinemia and arteriovenous fistula thrombosis in hemodialysis patients

BACKGROUND

To date, the relationship between vascular access (VA) failure and plasma total homocysteine level has been investigated only in mixed dialysis populations (ie, patients with a native arteriovenous [AV] fistula or arterial graft), whereas almost no data exist for hemodialysis patients with a native AV fistula.

METHODS

In this prospective cohort study, we examined the relationship between plasma total homocysteine level and the methylenetetrahydrofolate reductase (MTHFR) gene and VA-related incident morbidity in a cohort of 205 hemodialysis patients, all with a native AV fistula.

RESULTS

During follow-up, 78 patients experienced 1 or more VA thrombotic episodes. Patients with incident VA thrombosis had a significantly greater plasma total homocysteine level compared with patients without this event (P = 0.046). In Kaplan-Meier survival analysis, the hazard ratio for VA thrombosis increased in parallel with homocysteine level, such that patients in the third homocysteine level tertile had a relative risk for this outcome 1.72 times (95% CI, 1.21 to 2.24) greater than in those in the first tertile (log-rank test, 6.81; P = 0.009). In a multiple Cox regression model, plasma total homocysteine level was confirmed to be an independent predictor of AV fistula outcome. Plasma total homocysteine level was significantly greater (P < 0.001) in patients with the TT genotype of the MTHFR gene than in those with the CT or CC genotype.

CONCLUSION

VA thrombosis in dialysis patients is associated with hyperhomocysteinemia. Intervention studies are needed to clarify whether decreasing plasma homocysteine concentrations may prevent VA failure in hemodialysis patients.

In uremia, plasma levels of anti-protein C and anti-protein S antibodies are associated with thrombosis

BACKGROUND

Vascular access thrombosis is an important cause of morbidity in patients with end-stage renal failure on maintenance hemodialysis (MHD). However, little is known about its risk factors. The present study was undertaken to evaluate the role of coagulation factors, fibrinolytic factors, and anti-phospholipid antibodies (aPL). In particular, we have evaluated the role of anti-protein C and anti-protein S antibodies in patients on MHD with and without thrombosis because no data are available in the literature.

METHODS

The study group comprised 30 patients with thrombotic complications (TC), 40 patients matched for age, sex, and dialytic age with no thrombotic complications (NTC) and 400 controls. We have measured: anti-protein C antibodies, anti-protein S antibodies, anticardiolipin antibodies (ACA), anti-beta2-glycoprotein antibodies (beta2-GPI), and anti-prothrombin antibodies (aPT), along with prothrombin time, fibrinogen, plasminogen, protein C, protein S, anti-thrombin III, APC-resistance test, D-dimer, tissue-type plasminogen's activator, plasminogen activator inhibitor-1 (PAI-1), prothrombin fragment 1+2, factors of the intrinsic and extrinsic pathway, C-reactive protein, and homocysteine.

RESULTS

There were no significant differences between groups for prothrombin time, fibrinogen, plasminogen, protein C, protein S, anti-thrombin III, activated protein C (APC) resistance, D-dimer, tPA, C-reactive protein, Factors II, X, and VII. The anti-beta2-GP1 and aPT were elevated in both TC and NTC patients, compared to the control group. Significant differences between TC and NTC groups were found for anti-protein C and anti-protein S antibodies, ACA-IgM, PAI-1, Factor VIII, prothrombin fragments 1+2, and homocysteine.

CONCLUSION

The most novel finding was a significant elevation of anti-protein C antibodies and anti-protein S antibodies in the TC group (i.e., in patients on MHD with thrombosis of vascular access). It indicates that other pathogenetic mechanisms in addition to endothelial damage may cause hypercoagulability in uremia.

The relationship between anticardiolipin antibodies and vascular access occlusion in patients on hemodialysis

Vascular access occlusion is frequently seen in some patients on hemodialysis. There are different opinions about pathogenesis of recurrent access thrombosis. Anticardiolipin (aCL) antibodies have been suggested to be involved in thrombosis and can be found in a high proportion of patients with chronic renal failure. We investigated the relationship between vascular access occlusion and the level of aCL antibodies in hemodialysis patients. We measured serum IgG and IgM aCL antibodies and protein C levels in 50 patients on hemodialysis having no fistule thrombosis (group 1), in 33 patients on hemodialysis with fistule thrombosis (group 2), and 20 nondialyzed patients with chronic renal failure (group 3). There were no differences in age and duration on hemodialysis (p > 0.05). No significant correlation was found between protein C and platelet counts in all groups (p > 0.05). In group 1, aCL IgG and IgM were 2%. In group 2, aCL IgG and IgM were 6.06% and 0%, respectively. In group 3, aCL IgG and IgM were negative. We did not find any significant difference between aCL IgG and IgM in all groups (p > 0.05). No association was found between aCL antibodies and vascular access thrombosis in our patients on hemodialysis.

Anticardiolipin antibody and Taiwanese chronic haemodialysis patients with recurrent vascular access thrombosis

Vascular access failure is a major cause of morbidity in chronic haemodialysis (HD) patients. However, some factors (such as homocysteine levels) are known regarding the risk factors predisposing certain HD patients to vascular access thrombosis (VAT). Immunoglobulin-G anticardiolipin antibody (IgG-ACA) is strongly associated with venous and arterial thrombosis in patients with normal renal function. Previous investigations have reported the characteristics of patients with raised IgG-ACA titre and recurrent VAT of HD in Western countries, but few equivalent studies exist for Taiwan. This retrospective study attempts to determine whether raised IgG-ACA titres are associated with an increased risk of recurrent VAT in chronic HD patients. This study enrolled 483 patients undergoing HD. IgG-ACA titre and hepatitis B&C marker were measured for all patients. A history of recurrent (VAT more than one) and/or VAT was elicited by using information from the patient questionnaires and was verified by means of careful inpatient and outpatient chart review. Raised IgG-ACA titres were present in 21.7% (105/483) of patients. In both groups (raised IgG-ACA and normal IgG-ACA), the type of shunt differed significantly (p = 0.029). In predicting for more or one episodes of VAT by using multiple logistic regression with all significant factors, synthetic graft was also a significant factor (p < 0.0001). The 105 raised IgG-ACA titres and 378 normal IgG-ACA titres were associated between chronic HD patients and recurrent VAT (p = 0.034). In predicting for more or one episode of VAT by using multiple logistic regression with all significant factors, raised IgG-ACA titre was a non-significant factor (p = 0.336). The presence of hepatitis C had a higher percentage in group with raised IgG-ACA titres of HD patients (p = 0.042). In predicting for more or one episode of VAT by using multiple logistic regression with all significant factors, the presence of hepatitis C was also a significant factor (p = 0.022). In conclusion, the prevalence of raised IgG-ACA titres was 21.7% among HD patients. There was a weak association between raised IgG-ACA titre and recurrent VAT and this finding may be the consequence of pathogenetic role of raised IgG-ACA titres in the development of VAT status for chronic HD patients. The presence of hepatitis C was a cofactor.

Homocysteine and vascular access thrombosis in a cohort of end-stage renal disease patients

BACKGROUND

Maintaining successful hemodialysis services is dependent upon an access to circulation that is reliable and stable. Complications of vascular access such as dysfunction, thrombosis, or infection are major causes of hospitalization with thrombosis being the most common reoccurring problem. Initial prospective evidence supports an independent association between total homocysteine (tHcy) levels and access thrombosis. The purpose of this study was to determine if significant associations exist between tHcy, age, gender, and vascular access thrombosis in patients with end-stage renal disease (ESRD).

SUBJECTS AND METHODS

One hundred eighty-five (N=185) patients undergoing dialysis were selected as subjects. The retrospective sample was divided into a one or less vascular access thrombosis (VAT) (VAT) group (n= 133) and more than one (VAT II) VAT group (n= 52). The data was collected during a 16-month period (January 2000 to April 2002). Additional subgroup analyses included gender and age.

RESULTS

The Mann-Whitney U nonparametric t-Test for variance between groups revealed no significant difference in tHcy values between VAT groups (U=1841.50, p=0.284). A two-sample t-Test for variance between tHcy and age revealed no significant differences (F-ratio = 0.832, p = 0.32). A chi-square analysis revealed no significant differences in gender and VAT groups (chi2=0.246, p=0.62). A Kolmogorov-Smirnov test for normality was calculated for tHcy with a p-value of 0.859 revealing insufficient evidence that the distribution is not normal. Spearman Rank Correlations were calculated, revealing low to moderate associations among variables.

CONCLUSIONS

While some studies have demonstrated a relationship between tHcy and VAT, this study found that chronically high homocysteine levels in patients with ESRD were not associated with incidence of VAT. There were no significant differences in the number of VATs across additional variables of age and gender.

Comparison of hemodynamic changes associated with two different polytetraflouroethylene arteriovenous fistulae in hemodialysis patients

The aim of this prospective study was to identify hemodynamic factors associated with two different types of polytetrafluroethylene (PTFE) AV grafts. The study was conducted on 46 hemodialysis patients over a 3-year period. The subjects were randomly assigned to one of two study groups: Group 1 patients (n = 24) underwent a brachiocephalic loop PTFE fistula; Group 2 patients (n = 22), a brachioaxillary PTFE fistula. Preoperatively, we recorded each individual's subclavian catheter history, hemodialysis frequency, and serum levels of parathormone (PTH), calcium (Ca)-phosphorus (P) product, homocysteine, protein C, and protein S. Doppler ultrasonography was used to evaluate vascular hemodynamic changes in the proximal and distal portions of the AV fistula at 48 hours and 1 week postoperatively. Group 1 showed a significantly greater number of ipsilateral subclavian catheter interventions prior to AV graft surgery than Group 2 (14 versus 7, respectively; P = .05; chi-square). The mean peak systolic velocity in the brachial artery in Group 1 was significantly higher than that in Group 2 at 1-week postoperatively (P = .04, paired t-test). The mean radial artery diameter in Group 1 was greater than that of Group 2 at 1 week postoperatively (P = .05, Student t-test). At 48 hours postoperatively the observed change in cephalic vein diameter in Group 1 was significantly greater than the change in axillary vein diameter in Group 2 (P = .08, paired t-test). Preoperatively, the mean serum protein C and protein S levels in Group 1 were higher than those in Group 2 (P = .03 and P = .04, respectively; Mann-Whitney U test). The total numbers of dialysis sessions per week in each group were significantly different (P = .001, chi-square). Six Group 1 patients exhibited graft thrombosis at 48 hours after AV graft surgery. None of the patients in Group 2 exhibited thrombosis at 48 hours or 1 week postoperatively. The results indicate that patients with brachiocephalic PTFE AV grafts show more significant changes in the cephalic vein and brachial artery than patients with brachioaxillary PTFE AV grafts. The findings also suggest that more ipsilateral subclavian catheter interventions and a higher weekly frequency of hemodialysis prior to AV graft surgery are risk factors for early thrombosis of PTFE AV grafts.

Significance of anticardiolipin antibodies on short and long term allograft survival and function following kidney transplantation

The significance of anticardiolipin antibodies (ACAs) prior to renal transplantation is unclear. We studied a cohort of 337 patients who underwent renal transplantation from 1996 to 2001. Follow-up continued until allograft loss, patient death or 31 December 2002. The primary outcome was a composite endpoint of death-censored allograft loss or a 25% reduction in estimated glomerular filtration rate (GFR) from 1-month post-transplant. Secondary outcomes were allograft loss, a 25% reduction in GFR, acute rejection and creatinine at 1 year. IgG and IgM ACA titers were positive (> or =15) in 18.1% of recipients. There were no significant differences at baseline between recipients, except coumadin therapy in those with positive ACA titers (20% vs. 7.4%). Post-transplant, there was no increase in the primary outcome in ACA-positive patients, even after adjustment for anticoagulation with coumadin (HR = 1.42 [0.68, 2.96]). There was no difference in secondary outcomes between those with or without positive titers. Two of five patients with very high titers (>50) who were not anticoagulated had early graft loss. A positive ACA titer prior to kidney transplantation was not associated with inferior renal outcomes after transplantation, although more research is required to address the prognostic significance of very high ACA titers.

Medical factors affecting patency of arteriovenous access

Arteriovenous access failure is multifactorial in nature with contributions from both medical and surgical etiologies. Medical causes of arteriovenous access failure are rare, and therefore infrequently identified as a major contributing source of malfunction. Although they account for only 10-15% of all cases of access failure, their importance should not be underestimated, especially in cases where a surgical source cannot be identified. Most medical causes are derived from Virchow's triad of endothelial cell injury, stasis, and hypercoaguability. Endothelial cell injury occurs through oxidative stress, activated platelets, increased levels of circulating tumor necrosis factor-alpha, and preexisting intimal hyperplasia. Stasis can occur through prolonged access compression, hypotension, or hypoalbuminemia. Finally, patients with renal failure requiring hemodialysis are frequently at increased risk for hypercoaguable states, except for situations of platelet dysfunction, and therefore access failure. Potential treatments include identifying and removing the offending source, as well as innovative, new medications to prevent their reoccurrence. Treatment is aimed at improving quality of life, as well as decreasing morbidity and hospital admissions in this difficult patient population.

Hypercoagulability in renal transplant recipients. Identifying patients at risk of renal allograft thrombosis and evaluating strategies for prevention

Renal transplantation improves survival and quality of life for patients with end-stage renal disease (ESRD). Improvements in immunosuppressive therapy have reduced early allograft loss due to acute rejection to very low levels. Early allograft loss, due to acute thrombotic complications, remains a constant and proportionally increasing complication of renal transplantation. Identifying risk factor(s) for thrombosis amenable to preventive strategies has been elusive. Epidemiological studies have attempted to define risk in terms of modifiable (drugs, dialysis modality, surgical procedure) and non-modifiable (age, diabetes mellitus, vascular anomalies) factors, or identify changes in coagulation or fibrinolysis promoting a more thrombotic state. Most recently the evolution of thrombophilia research has established the potential for inherited hypercoagulability to predispose to acute allograft thrombosis. Inheritance of the factor V Leiden (FVL), prothrombin G20210A mutation, or the presence of antiphospholipid antibodies (APA) may increase the risk of renal allograft thrombosis approximately 3-fold in selected patients. Patients with ESRD due to systemic lupus erythematosus (SLE) appear at particularly high risk of thrombosis, especially if they have either APA or detectable beta(2)-glycoprotein-1. Data for other hypercoagulable states such as hyperhomocystinemia or the C677T polymorphism of the methylenetetrahydrofolate reductase gene are deficient. Patients with APA, FVL, or prothrombin G20210A mutation also appear to have greater graft loss due to vascular rejection, possibly reflecting immunological injury upon the vascular wall exacerbated or induced by the prothrombotic state. While substantial in vitro data suggest cyclosporine is prothrombotic, an independent clinical association with allograft thrombosis is unproven. Interventions to reduce thrombotic risk including heparin, warfarin, and aspirin have been evaluated in both selected high-risk groups (heparin and warfarin) and unselected populations (heparin and aspirin). In unselected patients at low clinical risk, aspirin (75-150 mg/day) with or without a short period of unfractionated heparin (5000U twice a day for 5 days) appears to reduce the risk of renal allograft thrombosis significantly with a low risk of bleeding, especially when compared with low molecular weight heparins which risk accumulation in renal failure. In high-risk groups (identified thrombophilic risk factor, previous thrombosis, or SLE) longer period of heparin, with or without aspirin and maintenance with warfarin, should be considered. Re-transplantation following graft loss due to vascular thrombosis can be undertaken with a low risk of recurrence. Further prospective studies evaluating both putative risk factors and intervention strategies are required to determine whether routine clinical screening for thrombophilic factors is justified.

Transforming growth factor beta1 genotype polymorphisms determine AV fistula patency in hemodialysis patients

BACKGROUND

In hemodialysis patients with an arteriovenous (AV) fistula, access failure is primarily due to fistula stenosis, which predisposes to thrombosis and subsequent access loss. The risk for access failure differs interindividually, an observation that is independent from vascular anatomy in a significant number of patients. Fistula stenosis is histologically characterized by intimal hyperplasia, which is induced by growth factors, among which transforming growth factor beta1 (TGF-beta1) is of major importance. The quantitative production of TGF-beta1 interindividually differs due to polymorphisms in the gene region encoding the signal sequence of the cytokine. We hypothesized that the TGF-beta1 genotype, by influencing the development of arteriovenous fistula stenosis, determines the risk for vascular access failure.

METHODS

One hundred twenty patients who had undergone placement of an AV fistula for initiation of hemodialysis treatment were genotyped for the polymorphic bases at position +869 and +915 of the TGF-beta1 gene. The primary end-point was time from fistula placement to access failure.

RESULTS

AV fistula patency was significantly associated with the TGF-beta1 genotype (P = 0.0046); patency was 62.4% and 81.2% after 12 months for TGF-beta1 high and intermediate producers, respectively. In contrast, AV fistula patency neither differed between diabetic and nondiabetic patients, nor between patients with and without manifest cardiovascular disease.

CONCLUSION

Polymorphisms in the gene region encoding the signal sequence of TGF-beta1 influence the risk for hemodialysis access failure. By inducing synthesis of extracellular matrix proteins, overproduction of TGF-beta1 may accelerate the development of intimal hyperplasia, resulting in fistula stenosis and subsequent access failure.

Thrombosis in end-stage renal disease

Although renal failure has classically been associated with a bleeding tendency, thrombotic events are common among patients with end-stage renal disease (ESRD). A variety of thrombosis-favoring hematologic alterations have been demonstrated in these patients. In addition, "nontraditional" risk factors for thrombosis, such as hyperhomocysteinemia, endothelial dysfunction, inflammation, and malnutrition, are present in a significant proportion of chronic dialysis patients. Hemodialysis (HD) vascular access thrombosis, ischemic heart disease, and renal allograft thrombosis are well-recognized complications in these patients. Deep venous thrombosis and pulmonary embolism are viewed as rare in chronic dialysis patients, but recent studies suggest that this perception should be reconsidered. Several ESRD treatment factors such as recombinant erythropoietin (EPO) administration, dialyzer bioincompatibility, and calcineurin inhibitor administration may have prothrombotic effects. In this article we review the pathogenesis and clinical manifestations of thrombosis in ESRD and evaluate the evidence that chronic renal failure or its management predisposes to thrombotic events.

The methylentetrahydrofolate reductase C677T point mutation is a risk factor for vascular access thrombosis in hemodialysis patients

BACKGROUND

Many reports indicate that a high homocysteine (Hcy) level is a potential risk factor for such thrombotic diseases as arteriosclerosis, myocardial infarction, and cerebral infarction in healthy individuals or hemodialysis (HD) patients. The methylentetrahydrofolate reductase (MTHFR) C677T polymorphism has been reported to be closely related to plasma Hcy level.

METHODS

Using a cross-sectional design in this study, the relationship between arteriovenous fistula (AVF) obstruction and the MTHFR C677T point mutation was examined in 337 HD patients.

RESULTS

Results of multivariate analysis showed no significant influence of age, HD therapy duration, sex, or the presence of diabetes mellitus, cerebral infarction, or myocardial infarction. Only the presence of the MTHFR C677T polymorphism yielded a significant difference. Percentages of patients who experienced AVF obstruction were as follows: CC (12.6%), CT (20.3%), and TT (31.8%). The number of those who experienced obstruction was significantly larger with the TT than CC (P < 0.01). Moreover, total obstruction episode ratios were as follows: CC, 1 in 107.21 episodes/patient-month; CT, 1 in 74.08 episodes/patient-month; and TT, 1 in 50.33 episodes/patient-month. Episode percentages tended to be greater when the degree of mutation was greater, and a significant difference was observed between the CC and TT alleles (P < 0.01).

CONCLUSION

Although AVF obstruction is affected by numerous factors, there was a strong relationship between MTHFR C677T mutation and AVF obstruction. These findings suggest that the MTHFR C677T point mutation could serve as an important indicator in identifying susceptibility to AVF obstruction.

No Association between Hyperhomocysteinemia and Vascular Access Thrombosis in Chronic Hemodialysis

Purpose

Hyperhomocysteinemia, recognized as a risk factor for cardiovascular diseases, has also been related with controversy to vascular access thrombosis in hemodialysis. Our objective was to determine if such an association could be found in our hemodialysis population.

Methods

The survey was conducted in a cohort of 165 chronic hemodialysis patients. Their vascular access history was considered from hemodialysis initiation until November 1999, including the number of vascular accesses created (either native or synthetic fistulae), focussing on vascular access thrombotic events, and excluding primary vascular access dysfunction. Diabetes, hemoglobin, erythropoietin dose, anticoagulation, and methyltetrahydrofolate reductase (MTHFR) status were considered. Serum total homocysteine (tHcy) measures were sampled for all patients in June 1998 and repeated yearly. Patients had not been supplemented routinely with hydrosoluble vitamins until June 1998, after which all received DiaVite® (R&D Laboratories, CA, USA) daily.

Results

Median survival of native fistulae was significantly longer (81 months, 95%CI 35–127) than for synthetic fistulae (31 months, 95%CI 27–51). Median vascular access survival was reduced for diabetics vs non diabetics (28 vs 57 months) (P<0.05), whereas sex, age and smoking had no impact. No correlation was found between tHcy concentration and the number of vascular access thrombotic events; homozygotes for MTHFR had higher tHcy but no more vascular access thrombotic events. The 38 patients with a mean vascular access survival of less than 12 months (6±3 months) were compared to the 127 patients with a mean vascular access survival of ≥ 12 months (39±25 months) (P<0.05): no difference in their respective tHcy concentrations before and after DiaVite® introduction was found (31±13 and 20±8 vs 34±17 and 22±6 μmol/L), but the first group presented more numerous synthetic fistulae (p<0.0001), lower hemoglobin levels, and higher erythropoietin doses.

Conclusions

No significant association between hyperhomocysteinemia and vascular access thrombosis could be found in our population. DiaVite® introduction allowed a significant reduction in tHcy, but had no impact on vascular access survival, except for a slight but not significant reduction in the prevalence of vascular access thrombotic events during the year on DiaVite®. Potential benefits of approaches to reduce tHcy for vascular access time-life prolongation remain to be demonstrated.

Homocysteine and vascular access thrombosis in hemodialysis patients

BACKGROUND

Vascular access remains the Achilles' heel of successful hemodialysis, and thrombosis is the leading cause of vascular access failure. Hyperhomocystinemia is common in hemodialysis patients and is associated with venous and arterial thrombosis in patients without end-stage renal disease.

SUBJECTS AND METHODS

In the study, 65 hemodialysis patients with native arteriovenous fistula were included. Two groups of patients were defined: group A including 45 patients with their vascular access either never or only once thrombosed, and group B including 20 patients with two or more thromboses of their vascular access. We determined serum concentrations of total homocysteine (immunoassay, Abbott) in our patients.

RESULTS

In 63 (96.9%) patients, hyperhomocystinemia was presented. There was no statistically significant difference between group A and B regarding age, gender and duration of hemodialysis treatment. Total homocysteine concentrations were higher in group A (42.1 +/- 18.6 micromol/l) than in group B (36.1 +/- 18.1 micromol/l) patients but the difference was small and not statistically significant.

CONCLUSION

We found no significant differences in total homocysteine concentrations between group A (thrombosis non-prone) and group B (thrombosis prone) patients. Our results suggest that thrombosis of native arteriovenous fistulas may not be caused by hyperhomocystinemia in these patients.

Coronary artery disease in uremia: Etiology, diagnosis, and therapy

Cardiovascular disease is a major challenge to nephrologists, whether we deal with patients with pre-end-stage renal failure, on dialysis or after successful renal transplantation. It is the most common cause for death in patients with a functional allograft, and prevents many dialysis patients from being engrafted. Coronary artery disease is a diagnostic and therapeutic challenge, as it differs in some respects from that seen in non-uremic cohorts, and lacks much of the evidence-base on which therapeutic intervention rests. This review examines the experimental and clinical literature on cardiovascular disease in uremia, focusing on coronary artery disease. We focus on the incidence, presenting syndromes, screening tools, and interventions in the context of acute and chronic coronary syndromes. Recent evidence comparing coronary angioplasty, coronary artery stenting, and bypass surgery in subjects with renal failure is also reviewed. Coronary artery disease is more prevalent in uremia, more difficult to diagnose and less rewarding to treat compared to non-uremic subjects. Many more randomized trials are needed. In the absence of information from such trials, we advocate aggressive control of conventional and novel cardiovascular risk factors, and early intervention for symptomatic coronary disease.

Impaired T cell proliferation, increased soluble death-inducing receptors and activation-induced T cell death in patients undergoing haemodialysis

Haemodialysis is a widespread option for end-stage renal disease (ESRD). Long-term success of dialysis is, however, limited by a high rate of serious bacterial and viral infections. We compared T cell functions in ESRD patients undergoing haemodialysis (n = 20), or were not dialysed and received conventional medical treatment (n = 20). Healthy volunteers (n = 15) served as controls. The T cell phenotype was examined by immunofluorescence using fluorochrome-labelled monoclonal antibodies and FACS analysis. The concentration of soluble CD95/Fas and of tumour necrosis factor-alpha receptor type 1 (sTNFR1) in the sera was quantified by ELISA. Activation-induced programmed T cell death was triggered by anti-CD3/CD28 antibodies and measured by 7-AAD staining. All immunological tests were performed at least 1 month after dialysis initiation. T cell proliferation in response to phytohaemagglutinin or anti-CD3 monoclonal antibodies was moderately diminished in non-dialysed patients and markedly reduced in haemodialysis patients compared to healthy controls (P < 0.01 and P < 0.001, respectively). In a mixed lymphocyte culture the proliferative response of T cells from dialysed patients was significantly diminished (P < 0.001). T cells of both non-dialysed and dialysed patients have augmented CD95/Fas and CD45RO expression, increased sCD95/Fas and sTNFR1 release and spontaneously undergo apoptosis. Culture of T cells from haemodialysis patients with anti-CD3/CD28 antibodies increased the proportion of CD4(+) T cells committing activation-induced cell death by a mean 7.5-fold compared to T-helper cells from non-dialysed patients (P < 0.001). Renal failure and initiation of haemodialysis results in a reduced proliferative T cell response, an aberrant state of T cell activation and heightened susceptibility of CD4(+) T cells to activation-induced cell death.

Severe atherosclerotic changes, including aortic occlusion, associated with hyperhomocysteinaemia and antiphospholipid antibodies

Three patients are described with severe systemic atherosclerosis, including aortic occlusion, in the presence of a spectrum of risk factors, including hypercholesterolaemia, hypertension, a positive family history of cardiovascular problems, and hyperhomocysteinaemia. In all three patients high levels of anticardiolipin antibodies were found. The possible pathogenic role of antiphospholipid antibodies in atherosclerosis in the context of hyperhomocysteinaemia in these patients is discussed.

Associations of homocysteine, C-reactive protein and cardiovascular disease in patients with renal disease

In the past year, evidence from epidemiological studies in patients with renal disease has confirmed associations between both elevated plasma total homocysteine concentrations and the inflammatory marker C-reactive protein with an increased risk of arteriosclerotic vascular disease. However, it remains to be determined whether lowering total homocysteine or reducing inflammation will prevent 'hard' clinical outcome events such as stroke, myocardial infarction, and vascular death. Randomized trials of homocysteine lowering are currently ongoing and should further clarify the nature of the observed association between elevated total homocysteine and cardiovascular risk in patients with or without renal disease, and whether it is causal and modifiable. There are currently no known therapeutic interventions that specifically lower C-reactive protein levels in individuals or the prevalence of elevated C-reactive protein in the population but randomized trials of anti-inflammatory therapy (e.g. using selective cyclo-oxygenase-2 inhibitors) aimed at preventing cardiovascular disease are currently being planned.

Role of homocysteine, cystathionine and methylmalonic acid measurement for diagnosis of vitamin deficiency in high-aged subjects

BACKGROUND

Intracellular B-vitamin and folate deficiency indicated by hyperhomocysteinemia is very frequent in the elderly population. Hyperhomocysteinemia increases the risk of atherothrombotic diseases and neuropsychiatric complications. Our aim was to evaluate the prevalence of increased serum metabolite concentrations in subjects of a higher age, and whether the measurement of metabolite concentrations is more effective in diagnosing B-vitamin deficiency than mere homocysteine.

MATERIALS AND METHODS

Homocysteine (HCY), cystathionine (CYS) and methylmalonic acid (MMA) were investigated in serum together with vitamin B-12, B-6 and folate in 90 high-aged subjects (85-102 years), 92 seniors (65-75 years), and in 50 younger subjects (19-50 years).

RESULTS

Elderly subjects (high-aged and senior) had elevated serum concentrations of metabolites. High-aged subjects had a higher frequency of pathological increases than seniors: HCY 62% vs. 24%; MMA 62% vs. 23%; CYS 81% vs. 36%. Folate and vitamin B-6 concentrations were significantly decreased in both elderly groups; vitamin B-12 was only decreased in high-aged subjects. Utilising vitamin B-6, B-12 and folate for diagnosis of intracellular vitamin deficiency, the rate was 30% in seniors and 55% in high aged subjects. However, utilising the metabolites (HCY, MMA and CYS) for the diagnosis of intracellular vitamin deficiency, there was a distinctly increased rate of 55% in seniors respective to 90% in high-aged subjects. Backward multiple regression analysis revealed that only folate, MMA, creatinine and age were independent variables influencing the HCY concentration. Furthermore, the MMA concentration was significantly and independently influenced by folate, vitamin B-12, HCY and creatinine, and the serum concentration of CYS by vitamin B-12, creatinine and age.

CONCLUSION

The metabolites HCY, MMA and CYS are sensitive indicators diagnosing impaired remethylation of homocysteine to methionine with parallel activation of catabolic pathway. Compared to mere HCY or B-vitamins in serum, the efficiency of diagnosing a disturbed HCY metabolism increases very much in utilising the metabolites HCY, MMA and CYS. For differential diagnosis, parallel measurement of folate and creatinine is recommended. The early and correct diagnosis of B-vitamin deficiency in elderly subjects is of high clinical relevance.

C-reactive protein, oxidative stress, homocysteine, and troponin as inflammatory and metabolic predictors of atherosclerosis in ESRD

Mortality in patients with end-stage renal disease remains high, with cardiovascular disease accounting for half of these deaths. Novel risk factors such as inflammation, oxidative stress, hyperhomocysteinemia, and high troponin levels are associated with cardiovascular risk in the general population. While there are substantial epidemiologic data confirming that these novel risk factors are associated with cardiovascular risk in end-stage renal disease patients, a causal relationship has not been established. Inflammation is readily identified by the presence of high levels of C-reactive protein, while studies of oxidative stress are hampered by the lack of a standardized test. The cause of both is unknown. Hyperhomocysteinemia results from decreased remethylation to methionine, although vitamin supplementation only partially corrects the defect, suggesting that uremic inhibition of the enzymatic process may be important. The most promising strategies for correcting oxidative stress and hyperhomocysteinemia are vitamin E and folinic acid therapy, respectively. Troponin I appears to be a more specific marker of myocardial injury than Troponin T, but troponin T retains its ability to predict cardiovascular mortality as well as all-cause mortality. Sorting out the role of each of these risk factors may be difficult since the factors may influence each other, may increase oxidative stress, and may mediate atherosclerosis through oxidative modification of lipids.

Renal allograft thrombosis: can thrombophilia explain the inexplicable?

Renal allograft thrombosis remains a preventable cause of early allograft thrombosis. It should not be considered simply an unpredictable and poorly understood consequence of surgery. Extrapolated data from the general population and early data from renal patients supports the concept that the interplay of non-inherited hypercoagulability of renal disease with inherited thrombophilia, and the altered environmental milieu of transplantation predisposes to thrombosis (summarized in Figure 2). We should not accept the inevitability of a constant attrition of grafts to thrombosis and need to continue to identify risk factors and confirm appropriate screening and interventions for its prevention, almost certainly requiring collaborative multicentre trials. In the future, just as we now expand the specificity of HLA gene typing with molecular biology, genotyping for recognized thrombophilia genes in patients at risk will expand our ability to recognize and prevent thrombosis with targeted interventions drawn from the increasing array of anticoagulants now available. The contribution of thrombophilia to non-immune mechanisms of chronic allograft loss is also a potentially important but neglected area of research.