New Study Shows Vasc-Alert Surveillance Technology Successfully Predicts Vascular Access Blockages in Dialysis Patients
Backgrounds: Clinical monitoring is the recommended standard for identifying dialysis access dysfunction; however, clinical monitoring requires skill and training, which is challenging for understaffed clinics and overburdened healthcare personnel. A vascular access risk stratification score was recently proposed to assist in detecting dialysis access dysfunction.
Purpose: Our objective was to evaluate the utility of using vascular access risk scores to assess venous stenosis in hemodialysis vascular accesses.
Methods: We prospectively enrolled adult patients who were receiving hemodialysis through an arteriovenous access and who had a risk score ⩽3 (low-risk) or ⩾8 (high-risk). We compared the occurrence of access stenosis (>50% on ultrasonography or angiography) between low-risk and high-risk groups and assessed clinical monitoring results for each group.
Results: Of the 38 patients analyzed (18 low-risk; 20 high-risk), 16 (42%) had significant stenosis. Clinical monitoring results were positive in 39% of the low-risk and 60% of the high-risk group (p = 0.19). The high-risk group had significantly higher occurrence of stenosis than the low-risk group (65% vs 17%; p = 0.003). Sensitivity and specificity of a high score for identifying stenosis were 81% and 68%, respectively. The positive predictive value of a high-risk score was 65%, and the negative predictive value was 80%. Only 11 (58%) of 19 subjects with positive clinical monitoring had significant stenosis. In a multivariable model, the high-risk group had seven-fold higher odds of stenosis than the low-risk group (aOR = 7.38; 95% CI, 1.44–37.82; p = 0.02). Positive clinical monitoring results and previous stenotic history were not associated with stenosis. Every unit increase in the score was associated with 34% higher odds of stenosis (aOR = 1.34; 95% CI, 1.05–1.70; p = 0.02).
A calculated risk score may help predict the development of hemodialysis vascular access stenosis and may provide a simple and reliable objective measure for risk stratification.
Lalathaksha Kumbar , Brad C Astor, Anatole Besarab, Robert Provenzano, Jerry Yee
- The Journal of Vascular Access, 2022
Development and validation of a risk score to prioritize patients for evaluation of access stenosis
Background: Access flow dysfunction, often associated with stenosis, is a common problem in hemodialysis access and may result in progression to thrombosis. Timely identification of accesses in need of evaluation is critical to preserving a functioning access. We hypothesized that a risk score using measurements obtained from the Vasc-Alert surveillance device could be used to predict subsequent interventions.
Methods: Measurement of five factors over the preceding 28 days from 1.46 million hemodialysis treatments (6163 patients) were used to develop a score associated with interventions over the subsequent 60 days. The score was validated in a separate dataset of 298,620 treatments (2641 patients). Results: Interventions in arteriovenous fistulae (AVF; n = 4125) were much more common in those with the highest score (36.2%) than in those with the lowest score (11.0). The score also was strongly associated with interventions in patients with an arteriovenous graft (AVG; n = 2,038; 43.2% vs. 21.1%). There was excellent agreement in the Validation datasets for AVF (OR = 2.67 comparing the highest to lowest score) and good agreement for AVG (OR = 1.92).
This simple risk score based on surveillance data may be useful for prioritizing patients for physical examination and potentially early referral for intervention.
Astor BC, Hirschman K, Kennedy J, Frinak S, Besarab A.
—Semin Dial., October 12, 2021
Sentinel Vascular Access Monitoring after Endovascular Intervention Predicts Access Outcome
Analysis of 138 subjects (females 51%; Black 87%) included 64 arteriovenous fistulas with 104 angioplasties and 74 arteriovenous grafts with 134 angioplasties. The area under the receiver operating characteristic curve for fistula failure at 3 months was 0.59, with optimal screening characteristics of 33.3%, sensitivity of 56.1%, and specificity of 63.2%. Arteriovenous fistula with <33.3% decline compared to >33.3% required earlier subsequent procedure (136 vs 231 days), lower survival on Kaplan–Meier analysis (P = 0.01), and twofold greater risk of failure (P = .006). Area under the receiver operating characteristic for arteriovenous graft failure at 3 months had a sensitivity of 52.3% and specificity of 67.4%. Arteriovenous graft with a post-intervention vascular access pressure ratio decline of <28.8% also required earlier subsequent procedure (144 vs 189 days), lower survival on Kaplan–Meier (P = 0.04), and a 59% higher risk for failure. The area under the receiver operating characteristic curve for combined access failure (arteriovenous fistula + arteriovenous graft) at 3 months had an optimal cut-point value of 31.2%, a sensitivity of 54.6%, and a specificity of 63.1%. Access with a <31.2% drop had a 62% increase in the risk of failure (hazard ratio 1.62; confidence interval 1.16, 2.27; P = 0.005).
The magnitude of post-intervention reduction in vascular access pressure ratio provides a novel predictive measure of access outcomes.
Lalathaksha Kumbar, Ed Peterson, Matthew Zaborowicz, Anatole Besarab, Jerry Yee, Gerard Zasuwa
—The Journal of Vascular Access, 2018
The “Unappreciated” Other Half of Vascular Access Success
Extending the life of an AV access (survival) is the goal of an access maintenance program. To determine if the use of Vasc-Alert extended the life of accesses, treatment data was examined at 15 facilities that were considered to have good vascular access maintenance programs. 494 Pts were identified to have started on a new access (389 AVF, 105 AVG). These accesses were then followed forward in time for 4-years until they either transitioned to a new access or the end of the 4-year period, with the results being entered into a Kaplan-Meier survival curve. For comparison, 13 published studies (2,508 Pts) using Kaplan-Meier analysis for AV access patients were examined and combined into a median result. The Kaplan-Meier survival rate for 389 AVF accesses at facilities using Vasc-Alert was 79% at 48 months compared to an expected benchmark survival of 44%. The survival of 105 AVG was 67% at 36 months compared to the benchmark of 35%.
The results of the survival analysis indicate that Vasc-Alert, in concert with a vascular access management program, extending the patency of both AVF and AVG.
Anatole Besarab, John Kennedy, Chaim Charytan, Kim Hirschman, Farhanah Yousaf
—Poster presented at NIH meeting on vascular access, 2015
The Usefulness of Vasc-Alert to Identify Significant Dialysis Access Stenosis
One hundred twenty-nine (129) patients were sent for diagnostic angiography. All but five (5) patients (3.8%) had a significant stenosis and were successfully treated with angioplasty. No patients had a thrombosis episode in the study period. None missed any dialysis treatments and the stenosis pre-procedure was significantly less than those sent from other methods of surveillance (71% stenosis for study patients vs. 89% for patients referred from other surveillance methods).
Vasc-Alert is an effective tool to detect VA stenosis.
Gerald A. Beathard, MD, PhD, FASN, Aris Q. Urbanes, MD, Terry Litchfield
—ASN Conference poster, 2012
Automated Intravascular Access Pressure Surveillance Reduces Thrombosis Rates
Thrombosis rates declined progressively for arteriovenous grafts (AVG) during the 18-month intervention period compared with the 6-month baseline period. Arteriovenous fistula (AVF) thrombosis rates decreased during post-intervention months 13-18 during employment of the Vasc-Alert. Combined AVG and AVF thrombosis rates declined from 0.297 events per person-yr to 0.133 at the completion of the 18 intervention period, a decline of 55%.
The use of Vasc-Alert can reduce thrombosis rates in vascular accesses, and the magnitude of the effect is larger and more consistent in arteriovenous grafts (AVGs) than autologous AVFs.
Gerard Zasuwa, Stanley Frinak, Anatole Besarab, Edward Peterson, Jerry Yee
—Semin Dial., Sep-Oct 2010
Mathematical Model Demonstrates Influence of Luminal Diameters on Venous Pressure Surveillance
It was found that there is an approximate one-to-one relation between MAP and VP, so VP/MAP is a valid adjustment. Also, the 0.50 threshold successfully identifies most grafts with stenosis of 65% or more. However, the ratio of artery/vein diameters varied widely between patients, and the ratio independently influences VP/MAP. When the inflow artery is relatively narrow, the VP/MAP increase is delayed followed by a more rapid increase as critical stenosis is reached.
VP/MAP is a valid adjustment for the influence of MAP on VP, and the standard VP/MAP threshold of 0.50 warns of the transition to critical stenosis. However, relatively narrow arteries cause a delay followed by a rapid increase in VP/MAP that may not be detected before thrombosis unless measurements are very frequent.
John J. White, Steven A. Jones, Sunanda J. Ram, Steve J. Schwab, and William D. Paulson
—Clin J Am Soc Nephrol 2: 681-687, 2007
Vasc-Alert is an Effective Tool to Predict Venous Stenosis
110 subjects were sent for 133 venograms. 20 patients had a thrombotic event. The events were analyzed and sensitivity and specificity were found to be 90%. The positive predictive value was 93%, with a negative predictive value of 88%. The false-positive rate was 10%. Fistulas showed more central lesions than grafts.
Vasc-Alert is a clinically useful tool to predict venous stenosis.
Mary Hammes, D.O., Brian Funaki, MD, Kim Hirschman, M.A., John Kennedy, MBA, Ogbannaya Aneziokoro, MD
—ASN Conference poster, 2005
Dynamic venous access pressure ratio test for hemodialysis access monitoring.
During a 3-month interval, 120 HD patients with AVGs were assessed by Vasc-Alert while access outcomes were monitored for another 3 months. Sensitivity and specificity for detection of a graft event were 70% +/- 8% and 88% +/- 2% and increased to 74% +/- 5% and 92% +/- 3% at 6 months, respectively.
The Vasc-Alert test is a valuable tool to prospectively monitor for adverse AVG events.
Stanley Frinak,, Gerard Zasuwa, Thomas Dunfee, Anatole Besarab, Jerry Yee
—Am J Kidney Dis., Oct 2002