Duplex ultrasound of vascular access for hemodialysis thrombosis

Introduction. The most common complication of the vascular access for hemodialysis, that can lead to its loss, is thrombosis. The method of choice in diagnosing fistula thrombosis is duplex ultrasound. Purpose: to study the ultrasound signs and changes in hemodynamics data in thrombosed fistulas and to determine the risk factors contributing to its development. Materials and methods. Duplex ultrasound was performed in 550 patients with vascular access for hemodialysis. Access thrombosis was detected in 12,0%, non-occlusive thrombosis was observed in 60,6%, occlusive thrombosis — in 39,4%. Thrombosis was significantly more common in women than in men (p=0,025). In patients with graft, thrombosis was more common (24,2%) than in those with arteriovenous fistula (11,2%), p=0,026. A correlation was found between the presence of significant vascular access stenosis, aneurysm of the outflow vein or graft, and the development of thrombosis (p<0,02). Duplex ultrasound allows to diagnose vascular access thrombosis and to determine the causes of its development.

Feasibility of routine ultrasound-guided percutaneous transluminal angioplasty in the treatment of native arteriovenous fistula dysfunction

Background: Stenosis is the main cause of arteriovenous fistula failure and is due to neointimal hyperplasia. Percutaneous transluminal angioplasty is the gold standard for patients with vascular access stenosis. The aim of the study was to evaluate the efficacy and safety of ultrasound-guided percutaneous transluminal angioplasty in the treatment of native arteriovenous fistula venous stenosis. Methods: The need for intervention was determined by physical examination and duplex ultrasound in 162 patients. All patients with failing or not maturing arteriovenous fistula were treated in the outpatient setting under ultrasound guidance. Procedural success was assessed with repeated post-procedural ultrasound examinations. All procedures were performed under local anesthesia by a single nephrologist and were performed in a single vascular laboratory, while follow-up ultrasound was performed in the dialysis unit of destination. Results: Early technical success was obtained in 95.6% of cases (154 of 162). Complications occurred in 22 patients (13.5%) with no major complication requiring surgical or fluoroscopic endovascular intervention. Primary patency at 6 and 12 months was 84% and 69.8%, respectively. Risk factors for arteriovenous fistula failure/secondary percutaneous transluminal angioplasty were vascular access low blood flow rate and vintage, as well as the need for thrombolysis during the first percutaneous transluminal angioplasty. Conclusion: Ultrasound-guided percutaneous transluminal angioplasty is a valuable tool to treat vascular access stenosis.

Possible Roles of Periostin in the Formation of Hemodialysis Vascular Access Stenosis after Polytetrafluoroethylene Graft Implantation in Dogs

Periostin, a recently found matricellular protein, has been implicated in neointima formation after balloon injury. However, the relationship between periostin and hyperplastic intima formation after PTFE graft implantation is unclear. Under mixed anesthesia, PTFE grafts were implanted between the canine carotid artery and jugular vein, and PTFE graft samples were harvested 1, 2, and 4 months after implantation. Intima formation started on the luminal surface of PTFE grafts at the venous anastomotic region 1 month after implantation. Thereafter, the increase in intimal volume was not only observed in the venous and arterial anastomotic regions, but also in the middle region of the PTFE grafts. In accordance with the increased intimal formation, time-dependent increases in mRNA expressions of periostin and transforming growth factor beta 1 (TGF-β1), as well as a strong positive correlation between periostin and TGF-β1, were observed. These findings suggest that periostin may play a very important role in the pathogenesis of hemodialysis vascular access stenosis through the acceleration of intimal formation. Thus, periostin may be a very important therapeutic target for the treatment of vascular access graft dysfunction in hemodialysis patients.

Semiquantitative analysis of virtual histology derived from intravascular ultrasound images at vascular access stenosis

Vascular access failure, such as recurrent stenosis and thrombosis, is a major concern in patients with end-stage kidney disease. Neointimal hyperplasia development at the anastomosis site of outflow vessels is a primal cause for recurrent vascular access failure. We previously shed some lights into a role of vitamin D, which exerts a protective effect against neointimal hyperplasia formation. Virtual histology, derived from intravascular ultrasound technology, provides novel insights into plaque composition analysis in atherosclerotic diseases. However, there is so far a lack of evidence on the relation between virtual histology and pathophysiological findings. To elucidate this missing link, we comprehensively reviewed 10 chronic hemodialysis patients who underwent repeated intravascular ultrasound–guided balloon angioplasty. Their age, dialysis vintage, and follow-up period were 75.0 ± 4.24, 20.5 ± 2.12, and 11.5 ± 0.71 (mean ± standard deviation) years, respectively. Pathological cross-sectional analyses were performed using specimens from vascular access surgeries during the follow-up period. Interestingly, positive relation is found between virtual histology–constructed fibrous tissue and pathological neointimal hyperplasia. Strikingly, immunohistological analysis revealed that vitamin D receptor–positive myofibroblasts were abundantly distributed in the equivalent area to virtual histology fibrous tissue. Our 10-year follow-up data of resistant vascular access stenosis indicates strong correlation between vitamin D receptor–rich neointimal vessel hypertrophy and intravascular ultrasound–assisted virtual histological analysis. Intravascular ultrasound technology is one of the minimally invasive diagnostic tools to provide histologically relevant tissue structure information and help determine target vessel stenosis on vascular access.

Recent developments in endovascular interventions to sustain vascular access patency in haemodialysis patients

There is amassed evidence regarding the use of endovascular procedures for the treatment of vascular access stenosis and thrombosis. A review was conducted based on available randomized trials, cohort studies and retrospective analyses published after 2000 on endovascular treatment of dysfunctional and thrombosed vascular access, with an aim to illustrate the available device and procedural options. The use of paclitaxel-coated balloons, cutting balloons and covered stents is described in the field of vascular access stenosis. The broad spectrum of available devices and endovascular declotting procedures ranging from thrombolysis to thrombectomy is also discussed. Overall, in this review we demonstrate the increasing role of endovascular procedures in vascular access treatment and the improved patency outcomes provided by the implementation of novel endovascular devices. Moreover, the improvement of post-intervention primary patency rates after endovascular declotting procedures and the shift to more thrombectomy-dependent procedures over time is also highlighted. In conclusion, endovascular treatment of dialysis access stenosis and thrombosis has an established role, owing to the implementation of sophisticated devices, allowing, when needed, the simultaneous treatment of thrombosis and the underlying stenosis.