The effect of high-flow arteriovenous fistulas on systemic haemodynamics and brain oxygenation.

Aims: High-flow arteriovenous fistula (AVF) for haemodialysis leads to profound haemodynamic changes and sometimes to heart failure (HF). Cardiac output (CO) is divided between the AVF and body tissues. The term effective CO (COef) represents the difference between CO and AVF flow volume (Qa) and better characterizes the altered haemodynamics that may result in organ hypoxia.

Treatment of failing arterio-venous dialysis graft by angioplasty, stent, and stent graft: Two-years analysis of patency rates and cost-effectiveness.

The objective of this prospective randomized single-center study was to compare primary and secondary patency rates, number of percutaneous transluminal angioplasty (PTA) interventions and cost-effectiveness among PTA, deployment of a stent, or a stent graft in the treatment of failing arteriovenous dialysis grafts (AVG) due to restenosis in the venous anastomosis or the outflow vein. Altogether 60 patients with failing AVG and restenosis in the venous anastomosis or the outflow vein were randomly assigned to either PTA, placement of a stent (E-Luminexx) or stent graft (Fluency Plus). After the procedure, patients with stent or stent graft received dual antiplatelet therapy for the next three months.

Basilic Vein Transposition Used as a Tertiary Vascular Access for Hemodialysis: 15 Years of Experience.

Introduction: The quality of the life in patients requiring long term hemodialysis is directly proportional to the long-term patency of their vascular access. Basilic vein transposition for vascular access (BAVA) represents a suitable option for creating a tertiary native vascular access for hemodialysis on the upper extremities for patients requiring long term hemodialysis. The purpose of the study is to compare BAVAs with arteriovenous grafts (AVG).

Arteriovenous grafts: early ultrasonography tells their fortune.

Background: The patency of arteriovenous grafts (AVG) for hemodialysis is mostly limited by growing stenoses that lead to decreasing of blood flow, thromboses and finally to access failure. The aim of this study was to find out if detection of any pathology by duplex Doppler ultrasonography (DDU) early after creation of AVG could identify those with lower survival.

Methods: We retrospectively enrolled AVG examined by DDU in our center within 40 days after their creation during the last 10 years.

Long-term arterial adaptation to high blood flow in the feeding artery of vascular access for hemodialysis.

Purpose: Arteries continuously respond to changing tissue demands and to hemodynamic conditions by altering their diameter and wall structure. The relatively slow dilatation of the feeding artery of vascular accesses continues at least two years after access creation with a continuous decrease in wall shear rate (WSR), which however, remains highly supra-physiological. The aim of this study was to test the hypothesis that after a longer time period the WSR returns to its baseline value.

Low-flow polytetrafluoroethylene accesses: ultrasound surveillance and preemptive interventions ensure long-term patency.

Background: Vascular accesses (especially polytetrafluoroethylene grafts) with a permanently low flow (Qa <600 ml/min) are prone to thrombosis and thus have short patency. The reason for a permanently low flow is usually medial calcinosis of the inflow artery in diabetics. We retrospectively studied the long-term patency of low-flow grafts with careful ultrasound surveillance and preemptive interventions.

Short-term outcomes of borderline stenoses in vascular accesses with PTFE grafts.

Background: There are controversial data about vascular access stenosis surveillance by ultrasonography. The definition of stenosis significance varies among centres. We performed a retrospective study to describe short-term outcomes of borderline asymptomatic stenoses defined by precise criteria and to determine possible risk factors of stenosis progression.

Creation of dialysis vascular access with normal flow increases brain natriuretic peptide levels.

Background: Chronic heart failure is very common in hemodialyzed patients due to several factors such as intermittent volume overload, anemia, and hypertension. Dialysis access flow is usually considered to have a minor effect. We hypothesized that creation of dialysis access with "normal" flow would lead to elevation of B-type natriuretic peptide (BNP), which is a sensitive marker of heart failure.

Factors associated with impaired arterial adaptation to chronically high wall shear rate in the feeding artery of PTFE grafts.

Background/aims: The feeding artery of dialysis vascular access is subjected to unusually high wall shear stress (WSS), a hemodynamic factor leading to vasodilatation, for at least several months after access creation. Physiologically, high WSS leads to compensatory endothelium-dependent vasodilatation. We supposed that the dilatation of the feeding artery continues to lower WSS during longer time period after access creation and that this process is limited by risk factors of endothelial dysfunction.

Diabetes and distal access location are associated with higher wall shear rate in feeding artery of PTFE grafts.

Background: Surgical creation of permanent vascular access for haemodialysis leads to considerable haemodynamic changes. They could be implicated in the pathogenesis of access complications, which limit access survival, especially in diabetics. Physiologically, the relation between arterial diameter and blood velocity is maintained by wall shear stress (WSS), which is directly related to both blood viscosity and wall shear rate (WSR = blood velocity/internal diameter).

Regular ultrasonographic screening significantly prolongs patency of PTFE grafts.

Background: Polytetrafluoroethylene (PTFE) dialysis grafts have considerably shorter patency than native arteriovenous fistulas, despite the use of a complex of screening monitoring methods (venous pressure, access flow). PTFE grafts are used often in subjects with depleted subcutaneous veins after previous abandoned accesses, so keeping the access patent is crucial. We hypothesized that regular duplex Doppler ultrasound screening for access stenoses, together with their sooner treatment, would prolong PTFE graft patency.

Dialysis access-associated steal syndrome: the role of ultrasonography.

Background: Ischemic steal syndrome is an infrequent, but potentially disabling complication of hemodialysis (HD) access creation. We analyzed the ability of duplex Doppler ultrasonography to reveal potential causes of ischemic steal syndrome in antebrachial accesses.

Methods: We performed 212 examinations on 121 patients.

Many clinically silent access stenoses can be identified by ultrasonography.

Background: Stenoses of vascular accesses are leading factors limiting access survival. Besides physical examination, screening of access stenoses is based mainly on the "dysfunction hypothesis", which states that progressive stenosis causes graft dysfunction, such as decreased flow. We tested whether Doppler ultrasonography could detect a number of clinically hidden access stenoses in otherwise well-managed patients.

Endovascular treatment of central vein stenoses and/or occlusions in hemodialysis patients.

Purpose: To report our experience and results with the endovascular treatment of central vein stenoses and occlusions in hemodialysis patients.

Methods: Between October 1999 and August 2001 (22 months) we performed 22 interventional procedures in 14 hemodialysis patients (8 women, 6 men) ranging in age from 38 to 87 years (mean 76 years). The indication for intervention was stenosis (n = 10) or occlusion (n = 4) of a central vein in the upper arm used for dialysis in patients with arm swelling and/or shunt malfunction.