Pharmacological approaches to preventing vascular access failure

Role of Antiplatelet Therapy in Hemodialysis Arteriovenous Graft Secondary Patency Following Successful Percutaneous Thrombectomy

PURPOSE

The purpose of this study was to elicit the relationship of antiplatelet therapy (AP) in maintaining arteriovenous graft (AVG) patency after successful percutaneous pharmacomechanical thrombectomy ("declot").

MATERIALS AND METHODS

This was an institutional review board-approved retrospective review of AVG declot procedures between July 2019 and August 2020. AVG characteristics, bleeding complications, anticoagulation and antiplatelet medication regimens, and thrombosis free survival were evaluated. Recurrent time-to-event analysis was performed using a Prentice-Williams-Peterson Gap time model was performed to evaluate AVG thrombosis free survival.

RESULTS

A total of 109 declots were technically successful and performed in 63 individual patients. The majority of procedures were performed in upper arm grafts (71%, n = 45). Dual antiplatelet (DAPT) was prescribed after 52 declots (48%), single antiplatelet was prescribed after 36 declots (33%), and anticoagulation was prescribed after 31 declots (28%). Median thrombosis free survival was 37 days (range 1-412 days) in the no antiplatelet group, 84 days (range 1-427 days) in the single antiplatelet group, and 93 days (range 3-407 days) in the DAPT group. Anti-platelet medications trended towards protective of AVG thrombosis in multivariate analysis (hazard ratio 0.84, 95% confidence interval 0.60-1.19); however, this did not reach statistical significance (P = 0.33). A total of 4 major and 5 minor bleeding events occurred.

CONCLUSION

The results of this study support further evaluation of AP therapy in preventing secondary rethrombosis of dialysis AVG.

Catheter-related atrial thrombus: tip of the iceberg?

Although guidelines recommend catheters as a last resort for establishing a vascular access in patients undergoing dialysis, they continue to be used widely for this purpose. Catheter-related atrial thrombus (CRAT) is rarely reported in this group of patients, and it can lead to serious complications. The aim of this study was to determine the incidence of CRAT in patients undergoing hemodialysis with permanent-tunneled catheters. A total of 50 patients undergoing hemodialysis with permanent catheters were included in this study. The diagnosis of CRAT was based on transthoracic echocardiography findings. Thrombus was present in nine patients (18%) and related to the tip of the catheter in all cases. Except for one patient with two foci of thrombus, all patients had a single focus. There were no significant associations between the development of thrombus and the duration of catheter use or the location of the catheter. Furthermore, catheter-related atrial thrombus did not appear to have a significant effect on mortality. The asymptomatic character of CRAT can be responsible for the low reporting rates, and its exact role in increased mortality and morbidity related with catheter use remains unknown. While planning management strategies, information on different options for vascular access routes and possible catheter-related complications should be provided to all patients who will undergo dialysis, together with a discussion involving other replacement alternatives for end-stage renal disease.

Differences in coagulation in clotting of vascular access in hemodialysis patients

Arteriovenous graft (AVG) thrombosis is a frequent cause of graft failure. We evaluated coagulation protein concentrations, platelet function, and viscoelasticity factors in 20 hemodialysis (HD) patients with AVGs. The goal was to determine whether significant differences in protein concentrations, platelet function, and viscoelasticity factors exist among dialysis patients requiring frequent AVG declot procedures vs. those who do not. Twenty HD patients were enrolled: 10 frequent clotters (>3 declots in the previous year) and 10 were nonclotters. Patients on antiplatelets or chronic anticoagulation were excluded. Laboratories were drawn pretreatment and heparinase was added to counteract any potential heparin effect. Coagulation protein concentrations including tissue factor (TF), thrombin/antithrombin III complex (TAT), and prothrombin fragment 1 + 2 (F(1+2)) were assayed. The time to clot onset was measured by force onset time (FOT). Platelet contractile force (PCF) measured the force produced by platelets during clot retraction, whereas clot rigidity was measured as clot elastic modulus (CEM). FOT, CEM, and PCF were measured by Hemodyne. Both groups had upregulation of the TF pathway, as TF, TAT, and F(1+2) levels were similarly increased over baseline levels. Hemodialysis patients with frequent AVG clotting had higher levels of both PCF and CEM compared with nonclotters. Additionally, the frequent clotters had a lower FOT relative to nonclotters, although both were considered in the normal range. Our study suggests that HD patients with recurrent AVG thrombotic events form clots with higher tensile strength compared with HD patients without recurrent graft thrombosis.

Aspirin resistance in patients undergoing hemodialysis and effect of hemodialysis on aspirin resistance

The aim of this study was to evaluate the prevalence of aspirin resistance (AR) in patients undergoing hemodialysis (HD) and to assess the effect of HD on the results of the Multiplate test. A total of 54 patients undergoing HD were included in this study. Blood samples were taken just before and after the HD session. To determine AR, we used Multiplate test. Platelet aggregation values of the study population were 363.01 ± 225.69 aggregation unit (AU) × minutes before and 375.33 ± 254.05 AU × minutes after the HD (P = .597). There was strong correlation between the values before and after HD (R = .755, P < .0001). The AR status was changed in 9 (16.6%) patients after HD. Agreement of AR status before and after HD was substantial (κ coefficient = .667, P < .0001). The prevalence of AR in patients undergoing HD seems higher than in most of the studied populations, and this study has shown that the AR statuses of a significant number of patients undergoing HD change after an HD session.