The Impact of Arteriovenous Fistulae for Hemodialysis on the Cardiovascular System

Pulmonary hypertension and chronic kidney disease: prevalence, pathophysiology and outcomes

Pulmonary hypertension (PH) is common in patients with chronic kidney disease (CKD) or kidney failure, with an estimated prevalence of up to 78% in those referred for right-heart catheterization. PH is independently associated with adverse outcomes in CKD, raising the possibility that early detection and appropriate management of PH might improve outcomes in at-risk patients. Among patients with PH, the prevalence of CKD stages 3 and 4 is estimated to be as high as 36%, and CKD is also independently associated with adverse outcomes. However, the complex, heterogenous pathophysiology and clinical profile of CKD-PH requires further characterization. CKD is often associated with elevated left ventricular filling pressure and volume overload, which presumably leads to pulmonary vascular stiffening and post-capillary PH. By contrast, a distinct subgroup of patients at high risk is characterized by elevated pulmonary vascular resistance and right ventricular dysfunction in the absence of pulmonary venous hypertension, which may represent a right-sided cardiorenal syndrome defined in principle by hypervolaemia, salt avidity, low cardiac output and normal left ventricular function. Current understanding of CKD-PH is limited, despite its potentially important ramifications for clinical decision making. In particular, whether PH should be considered when determining the suitability and timing of kidney replacement therapy or kidney transplantation is unclear. More research is urgently needed to address these knowledge gaps and improve the outcomes of patients with or at risk of CKD-PH.

Long-term impacts of different dialysis modalities on right ventricular function in patients with end-stage renal disease

BACKGROUND

Right ventricular dysfunction is a major cause of heart failure and mortality in end-stage renal disease patients. Scarce data is available regarding the comparison of echocardiographic right ventricular function in end-stage renal disease patients on hemodialysis (HD) and peritoneal dialysis (PD). The aim of the study was to evaluate the long-term impacts of different dialysis modalities on right ventricular function assessed by conventional echocardiography, in end-stage renal disease patients with preserved left ventricular function.

METHODS

The study included 120 patients grouped as follows: PD (n = 40), HD with arterio-venous fistula (n = 40), and healthy control subjects (n = 40). Conventional echocardiography was performed on all patients. A classification of right ventricular function was defined in HD patients by using tricuspid annular plane systolic excursion (TAPSE), right ventricular myocardial performance index (RV-MPI), fractional area change (FAC), and tricuspid lateral annulus systolic velocity (Sa) values. Correlation analysis was performed by using the right ventricular dysfunction score, clinical, and echocardiographic parameters.

RESULTS

The mean age of the study population was 51.9 ± 13.1 years and 47.5% were females. TAPSE and Sa velocity were found to be significantly lower and RV-MPI was significantly higher in patients undergoing HD, compared with control and PD patients. Logistic regression analysis showed that HD treatment was an independent risk factor for developing right ventricular dysfunction.

CONCLUSION

RV function was impaired in patients undergoing HD compared with patients on PD.

Hydraulic expansion facilitates remodeling of arteriovenous fistulas without increasing venous intimal hyperplasia in rabbits

Background

An arteriovenous fistula (AVF) is considered essential for chronic hemodialysis.

Objective

To determine the effects of hydraulic expansion on the intimal hyperplasia of an AVF.

Methods

We divided 12 healthy male New Zealand white rabbits into a control group (vein without special handling and direct anastomosis with an artery, n = 6) and a hydraulic expansion group (vein dilated by hydraulic pressure before anastomosis, n = 6). Histopathomorphology was examined with hematoxylin and eosin staining and immunohistochemistry. Analysis of covariance (ANCOVA) was used to compare the data between the groups.

Results

Immediately and 1 day after surgery, the diameter of the fistula vein in rabbits in the hydraulic expansion group was significantly larger than it was in the control group (P = 0.02 and 0.03 respectively), but not on subsequent days. After hydraulic expansion and before construction of the fistula, the wall of vein was noticeably thinner on macroscopic observation, and the anterior and posterior walls were indistinguishable. At 3 weeks after surgery in the hydraulic expansion group, cells in the vein wall were disordered, there were fewer elastic fibers, tissues from the endothelium to tunica externa were less dense, and there was less extracellular matrix than in the control group. Expression of connective tissue growth factor in the hydraulic expansion group was significantly less than that in the control group (P = 0.01). No differences were found in intimal thickness or immunohistochemistry scores for transforming growth factor-β1 between the groups.

Conclusion

Hydraulic expansion did not increase intimal hyperplasia of an AVF, but facilitates remodeling of AVFs in rabbits.

The Frailty Phenotype in Hemodialysis Patients and its Association with Biochemical Markers of Mineral Bone Disorder, Inflammation and Nutrition

INTRODUCTION

Frailty is a state of increased vulnerability to physical stressors. It is common in patients with end-stage renal disease (ESRD) who are on hemodialysis (HD).The aim of this study was to analyze the presence of frailty phenotype among HD patients and to evaluate their interrelationship with different biochemical markers.

METHODS

For the frailty assessment the Frailty Phenotype by Fried et al. was used, where frailty was reported if three of the following criteria were met: unintentional weight loss, self-reported exhaustion, weakness, slow walking speed and low physical activity. From 281 HD patients, 126 patients were frail, 58 were pre-frail (two criteria were met) and the rest of the study population were robust (97 patients). BMI was calculated for all patients and venous blood samples were taken to determine laboratory parameters for bone alkaline phosphatase (BAP), phosphate (P), potassium (K), C-reactive protein (CRP) and albumin.

RESULTS

Patients who were on HD longer than 60 months have more characters of frailty. (p=0.019). A statistically significant positive correlations between frailty score and BAP (rho = 0.189; p = 0.001), and CRP (rho = 0.233; p < 0.001) were observed, and significant negative correlations between frailty score and albumin (rho = - 0.218; p < 0.001) and K (rho = - 0.198; p = 0.001).

CONCLUSIONS

The associations of frailty with markers of mineral bone disorder, inflammation and nutrition indicate the importance of these parameters in the indirect assessment of the frailty phenotype in HD patients.

Vascular Access Perspectives in Patients After Kidney Transplantation

Introduction: More attention has been paid to the influence of arteriovenous fistula (AVF) on the cardiovascular system. In renal transplant recipients, some beneficial effect of an elective vascular access (VA) ligation was observed in patients with a high AVF flow. However, this strategy is not widely accepted and is in contradiction to the rule of vasculature preservation for possible future access. The aim of our study is to elucidate the vascular access function and VA perspective in the kidney transplantation (KTx) population.

Materials and Methods: KTx patients with a stable graft function were recruited to participate in this single center observational study (NCT04478968). The measurement of VA flow and vessel mapping for future vascular access was performed by a color Doppler ultrasound. The study group included 99 (63%) males and 58 (37%) females; the median age was 57 (IQR 48–64) years. The median time from the transplantation to the baseline visit was 94 (IQR 61–149) months. Median serum creatinine concentration was 1.36 (IQR 1.13–1.67) mg/dl.

Results: Functioning VA was found in 83 out of 157 (52.9%) patients. The sites were as follows: snuffbox in six (7.2%), wrist in 41 (49.4%), distal forearm in 18 (21.7%), middle or proximal forearm in eight (9.6%), upper-arm AV graft in one (1.2%), and upper-arm AVFs in nine (10.8%) patients, respectively. Blood flow ranged from 248 to 7,830 ml/min; the median was 1,134 ml/min. From the transplantation to the study visit, 66 (44.6%) patients experienced access loss. Spontaneous thrombosis was the most common, and it occurred in 60 (90.9%) patients. The surgical closure of VA was performed only in six (4%) patients of the study group with a functioning VA at the time of transplantation. Access loss occurred within the 1st year after KTx in 33 (50%) patients. Majority (50 out of 83, 60.2%) of the patients with an active VA had options to create a snuffbox or wrist AVF on the contralateral extremity. In a group of 74 patients without a functioning VA, the creation of a snuffbox or wrist AVF on the non-dominant and dominant extremity was possible in seven (9.2%) and 40 (52.6%) patients, respectively. In 10 (13.1%) patients, the possibilities were limited only to the upper-arm or proximal forearm VA on both sides. Access ligation was considered by 15 out of 83 (18.1%) patients with a patent VA.

Conclusions: In the majority of the patients, vascular access blood flow was below the threshold of the negative cardiovascular effect of vascular access. Creation of a distal AVF is a protective measure to avoid a high flow and preserve the vessels for future access. The approach to VA should be individualized and adjusted to the patient's profile.

Development of hyperacute high-output heart failure at access creation

High-output heart failure can occur in patients undergoing hemodialysis via permanent access. We have described two cases of hyperacute high-output heart failure. Two patients with multiple previous failed access attempts presented for redo access. Each patient experienced high-output heart failure in the operating room during access placement. A delay in the diagnosis led to the first patient's death, although early recognition led to successful treatment of the second patient. Hyperacute heart failure during access creation is uncommon. Early recognition of this complication is important because timely intervention can be life-saving.

Hemodynamic impact of VASQ device in vascular access creation

BACKGROUND

Native arteriovenous fistula is the preferred vascular access in term of functionality, efficiency and complication rate. Nevertheless, research continues to seek strategies to reduce the risk of neointimal hyperplasia and hemodynamic modification. The aim of the study was to evaluate the impact on hemodynamic of the VasQ device in arteriovenous fistulae creation.

METHODS

The analysis included patients who underwent to fistula creation with or without implantation of the VasQ device between May and September 2019. The hemodynamic parameters were evaluated pre-operatively and at a follow-up of 1, 3, 6 months. The patency and complication rate were evaluated.

RESULTS

Fifteen VasQ devices were implanted during 30 arteriovenous fistula surgery. The baseline patients features were similar between groups (VasQ treated/control). At baseline, preoperative arterial flow was similar; radial artery diameter at surgical site was 3.4 ± 0.8 mm in treated and 2.8 ± 0.5 mm in the control group. The mean arterial flow at 1 month was 480 ± 210 mL/min in treated and 561 ± 27 mL/min in the control group. At 3 months the mean arterial flow in treated was 645 ± 143 mL/min versus 824 ± 211 mL/min (p = 0.02) in the control group; at 6 months the arterial flow was 714 ± 146 mL/min versus 810 ± 194 mL/min (p = 0.05) in control group. The cardiac output flow at 6 months in the treated group was 4458 ± 928 mL/min versus 5599 ± 1355 mL/min (p = 0.05) in the control group. At 6 months the primary patency was 73% and 80% and the secondary patency 80% and 86% in treated compared to the control group, respectively. No VASQ device complications were recorded.

CONCLUSION

The analysis of these data suggested that using VasQ device could be protective against the hemodynamic modification that occur during arteriovenous fistulae creation.

Comparison of cardiovascular mortality in hemodialysis versus peritoneal dialysis

PURPOSE

Cardiovascular disease is a significant cause of morbidity and mortality in dialysis patients. With the increasing prevalence of dialysis patients, there is a need to systematically identify the epidemiology of cardiovascular disease in hemodialysis and peritoneal dialysis patients.

METHODS

A meta-analysis was conducted in reference to the MOOSE and PRISMA guidelines. Database searches were conducted on Medline and Embase on 17 March 2020. Meta-analysis of proportions was used to summarize the overall prevalence of events. Pairwise comparisons were used to compare between hemodialysis and peritoneal dialysis, and meta-regression was applied to identify the factors influencing disease.

RESULTS

A total of 28 studies were included in the review and prevalence of cardiovascular disease events including coronary artery disease, coronary artery complications, congestive heart failure, peripheral arterial disease, atrial fibrillation, and cardiovascular mortality were summarized. Atrial fibrillation (RR 1.287 CI 1.154-1.436, p < 0.001), congestive heart failure (RR 1.229 CI 1.074-1.407, p = 0.003), and peripheral arterial disease (RR 1.132 CI 1.021-1.255, p = 0.019) were more common in hemodialysis patients, but cardiovascular mortality was lower in hemodialysis relative to peritoneal dialysis patients. (RR 0.892 CI 0.828-0.960, p = 0.002).

CONCLUSION

The authors have found fewer cardiovascular events but higher cardiovascular mortality in patients on PD as compared to those on HD. Future research is required to establish the causality between dialysis modality and the cardiovascular outcomes described.

Multimodality Tachycardia-Induced Stress Testing Predicts a Low-Risk Group for Early Cardiovascular Mortality After Renal Transplantation

Background

Cardiovascular events remain a major cause of death in kidney transplant recipients. The optimal noninvasive workup to prevent peritransplant cardiac mortality remains contentious.

Methods

We conducted a retrospective analysis to assess the renal transplantation cardiovascular assessment protocol within a single-center population over a 5-year period. Asymptomatic patients aged less than 45 years with no history of cigarette smoking, without diabetes mellitus, and dialysis-dependent for less than 24 months did not undergo cardiac testing before listing. All other asymptomatic patients underwent a noninvasive, tachycardia-induced stress test, where a target heart rate of 85% predicted for age and gender was required. The primary endpoints were rates of acute myocardial infarction (AMI) and cardiovascular death at 30 days after renal transplantation.

Results

Between 2015 and 2019, 380 recipients underwent cardiac evaluation: 79 (20.8%) were deemed low cardiovascular risk and placed on the renal transplant waitlist without further assessment; 270 (71.1%) underwent a tachycardia-induced stress test; and 31 (8.1%) were deemed high risk and proceeded directly to invasive coronary angiography (ICA). In the 5-year follow-up, 3 patients (0.8%) experienced an AMI 30 days after renal transplantation, all of which occurred in the high-risk “direct to ICA” cohort. No events were documented in the low-risk cohort or in patients who had a negative tachycardia-induced stress test. There were no cardiovascular deaths within 30 days after transplantation.

Conclusion

A negative tachycardia-induced cardiac stress test, achieving 85% of predicted heart rate, was associated with a 0% AMI rate and no cardiovascular deaths at 30 days after renal transplantation.

Vascular access type and mortality in haemodialysis: a retrospective cohort study

Background

Haemodialysis patients have a high mortality rate. Part of this can be attributed to vascular access complications. Large retrospective studies have shown a higher mortality in patients dialysed with a catheter, which is mostly ascribed to infectious complications. Since we observe very little infectious complications in our haemodialysis patients, the aim of our study was to assess if we could still detect a difference in survival according to vascular access type.

Methods

Patients that started chronic haemodialysis treatment between 1/1/2007 and 31/12/2016 at the ‘Universitair Ziekenhuis Brussel’ were retrospectively studied. The time to death was studied as a function of the two main vascular access types using survival analysis, considering the type of vascular access at the initiation of dialysis or as time varying, and accounting for the available baseline characteristics.

Results

Of 374 patients 309 (82.6%) initiated haemodialysis with a catheter, while 65 patients initiated with an arteriovenous access. Vascular access type during follow-up did not change in 74% of all patients. A Kaplan Meier plot did not suggest a survival dependent on the vascular access type at start. An extended cox proportional hazard analysis showed that vascular access type was not independently correlated with mortality. However, age, history of congestive heart failure and active cancer at initiation of dialysis were independently associated with mortality.

Conclusions

In this retrospective cohort study, haemodialysis vascular access type was not independently correlated with patient survival, even after taking into account change of vascular access over time.

Lack of PCSK6 Increases Flow-Mediated Outward Arterial Remodeling in Mice

Proprotein convertases (PCSKs) process matrix metalloproteases and cytokines, but their function in the vasculature is largely unknown. Previously, we demonstrated upregulation of PCSK6 in atherosclerotic plaques from symptomatic patients, localization to smooth muscle cells (SMCs) in the fibrous cap and positive correlations with inflammation, extracellular matrix remodeling and cytokines. Here, we hypothesize that PCSK6 could be involved in flow-mediated vascular remodeling and aim to evaluate its role in the physiology of this process using knockout mice. Pcsk6^−/− and wild type mice were randomized into control and increased blood flow groups and induced in the right common carotid artery (CCA) by ligation of the left CCA. The animals underwent repeated ultrasound biomicroscopy (UBM) examinations followed by euthanization with subsequent evaluation using wire myography, transmission electron microscopy or histology. The Pcsk6^−/− mice displayed a flow-mediated increase in lumen circumference over time, assessed with UBM. Wire myography revealed differences in the flow-mediated remodeling response detected as an increase in lumen circumference at optimal stretch with concomitant reduction in active tension. Furthermore, a flow-mediated reduction in expression of SMC contractile markers SMA, MYH11 and LMOD1 was seen in the Pcsk6^−/− media. Absence of PCSK6 increases outward remodeling and reduces medial contractility in response to increased blood flow.

Effects of Arteriovenous Fistula on Blood Pressure in Patients With End-Stage Renal Disease: A Systematic Meta-Analysis

Background Central arteriovenous fistula ( AVF ) creation is under investigation for treatment of severe hypertension. We evaluated the effects of AVF for initiation of hemodialysis on systolic, diastolic, and mean arterial blood pressure in patients with end-stage renal disease. Methods and Results Data search included PubMed, Web of Science, and the Cochrane Library. A systematic review and meta-analysis of peer-reviewed studies reporting the effects of the creation/ligation of an AVF on blood pressure in patients with end-stage renal disease was performed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis), PRISMA -P (PRISMA for systematic review protocols), and ROBINS-I (Risk of Bias in Non-Randomized Studies) criteria by the Cochrane Bias Methods Group. All studies in which the results could have been biased by hemodialysis were excluded. A total of 14 trials including 412 patients with end-stage renal disease ( AVF creation, n=185; AVF ligation, n=227) fulfilled the criteria and were subsequently analyzed. Average blood pressure in patients with no/closed AVF was 140.5/77.6 mm Hg with a mean arterial blood pressure of 96.1 mm Hg. Following creation of AVF , systolic blood pressure significantly decreased by 8.7 mm Hg ( P<0.001), diastolic blood pressure by 5.9 mm Hg ( P<0.001), and mean arterial blood pressure by 6.6 mm Hg ( P=0.02), whereas after ligation systolic blood pressure increased by 5.2 mm Hg ( P=0.07), diastolic blood pressure by 3.8 mm Hg ( P=0.02), and mean arterial blood pressure by 3.7 mm Hg ( P=0.07) during short- to long-term follow-up. Conclusions Creation of AVF significantly decreases blood pressure in patients with end-stage renal disease, whereas blood pressure tends to increase after ligation. These findings illustrate the hemodynamic consequences of AVF which are under investigation for severe hypertension.

Cardiovascular Disease After Kidney Transplant

Renal transplantation is the preferred treatment for patients with end-stage kidney disease. However, despite successful kidney transplantation, cardiovascular disease (CVD) remains one of the major causes of patient death and hence graft loss. The antecedents of this increased risk reside within the development of end-stage kidney disease and dialysis. Risk factors for the development of CVD include diabetes, hypertension, and dyslipidemia. Other transplant-specific factors include the presence of a patent arteriovenous fistula and immunosuppressive therapy. Efforts to modify these factors should be strongly encouraged to improve long-term outcomes of transplant patients and reduce death from CVD in this at-risk patient population.

Spanish Clinical Guidelines on Vascular Access for Haemodialysis

Vascular access for haemodialysis is key in renal patients both due to its associated morbidity and mortality and due to its impact on quality of life. The process, from the creation and maintenance of vascular access to the treatment of its complications, represents a challenge when it comes to decision-making, due to the complexity of the existing disease and the diversity of the specialities involved. With a view to finding a common approach, the Spanish Multidisciplinary Group on Vascular Access (GEMAV), which includes experts from the five scientific societies involved (nephrology [S.E.N.], vascular surgery [SEACV], vascular and interventional radiology [SERAM-SERVEI], infectious diseases [SEIMC] and nephrology nursing [SEDEN]), along with the methodological support of the Cochrane Center, has updated the Guidelines on Vascular Access for Haemodialysis, published in 2005. These guidelines maintain a similar structure, in that they review the evidence without compromising the educational aspects. However, on one hand, they provide an update to methodology development following the guidelines of the GRADE system in order to translate this systematic review of evidence into recommendations that facilitate decision-making in routine clinical practice, and, on the other hand, the guidelines establish quality indicators which make it possible to monitor the quality of healthcare.

Application of a central iliac arteriovenous coupler device in severe treatment-resistant hypertension: a 3.5-year follow-up

OBJECTIVE

In patients with resistant hypertension, percutaneous placement of an iliac arteriovenous coupler device leads to a reduction of blood pressure (BP) via decreased total vascular resistance and improved arterial compliance. However, long-term efficacy and safety need to be further explored. We report on the first case of 3.5-year follow-up in a patient who underwent implantation of an iliac arteriovenous coupler device.

RESULTS

A patient with resistant hypertension was admitted to hospital. Despite treatment with six anti-hypertensive drugs, his BP was poorly controlled. Previously, he had undergone renal denervation, which did not cause a significant BP decrease. Therefore, an arteriovenous coupler device was implanted, leading to an immediate and significant BP decrease. The patient was discharged with an office BP of 122/71 mmHg. After 3 months, there was a sustained BP decrease (-14/9 mmHg), whereas later, it was fluctuant (office BP: 147-173/85-95 mmHg, ABPM: 153-166/81-94 mmHg) probably due to medication non-adherence confirmed by a urinary toxicological screening test. Follow-up right heart catheterization showed changes in hemodynamic parameters related to volume congestion, which were accompanied by progressive dyspnea and weight gain. This was controlled by an optimized diuretic therapy. Additionally, an invasive closure maneuver was performed, leading to an immediate BP increase after closure and a similar decrease after re-opening of the anastomosis, verifying its proper long-term function.

CONCLUSION

The implantation of an iliac arteriovenous coupler device appears to be a promising and effective method to decrease BP and therefore reduce cardiovascular risk in patients with severe, treatment-resistant hypertension.

Impact of Systemic Volume Status on Cardiac Magnetic Resonance T1 Mapping

Diffuse myocardial fibrosis is a key pathophysiologic feature in heart failure and can be quantified by cardiac magnetic resonance (CMR) T1 mapping. However, increases in myocardial free water also prolong native T1 times and may impact fibrosis quantification. Thus far, the impact of systemic patient volume status remains unclear. In this study, native T1 time by CMR was investigated in hemodialysis (HD) patients (n = 37) and compared with healthy controls (n = 35). Volume status was quantified by bioimpedance spectroscopy and correlated with CMR T1 time. While no differences between HD patients and controls were present with regard to age (p = 0.180), height (p = 0.535), weight (p = 0.559) and left ventricular (LV) ejection fraction (p = 0.273), cardiac size was significantly larger in HD patients (LV end-diastolic volume 164 ± 53 vs. 132 ± 26 ml, p = 0.002). Fluid overloaded HD patients had significantly longer native T1 times than normovolemic HD patients and healthy controls (1,042 ± 46 vs. 1,005 ± 49 vs. 998 ± 47 ms, p = 0.030). By regression analysis, T1 time was significantly associated with fluid status (r = 0.530, p = 0.009, post-HD fluid status). Our data strongly indicate that native CMR T1 time is significantly influenced by systemic volume status. As fluid overload is common in patients with cardiovascular diseases, this finding is important and requires further study.

Preoperative management of arteriovenous fistula (AVF) for hemodialysis

Native arteriovenous fistula (AVF) is the favorite access for hemodialysis (HD). The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) recommends its creation in most patients with renal failure. Unfortunately, intensive efforts to promote native AVF in patients with marginal vessels have increased the rate of primary fistula failure. A non-functioning fistula prompts the use of central venous catheter (CVC) that, unlike AVF, has been associated with an increased risk of morbidity and mortality among patients receiving HD. We believe that successful and timely AVF placement relies on the development of a multidisciplinary integrated preoperative program divided into five stages: (i) management of patients with advanced chronic kidney disease (CKD), (ii) management of preoperative risk factors for AVF failure, (iii) planning of native AVF, (iv) assessment of patient eligibility and (v) preoperative vascular mapping. Focusing specifically on native AVF, we review scientific evidence regarding preoperative management of this vascular access in order to favor construction of long-term functioning fistula minimizing development of severe complications.