Diagnostic accuracy of ultrasound dilution access blood flow measurement in detecting stenosis and predicting thrombosis in native forearm arteriovenous fistulae for hemodialysis.

BACKGROUND: Vascular access surveillance by ultrasound dilution blood flow rate (Qa) measurement is widely recommended; however, optimal criteria for detecting stenosis and predicting thrombosis in arteriovenous fistulae (AVFs) are still not clearly defined. METHODS: In a blinded trial, we evaluated the accuracy of single Qa measurement, Qa adjusted for mean arterial pressure (Qa/MAP), and decrease in Qa over time (dQa) in detecting stenosis and predicting thrombosis in an unselected population of 120 hemodialysis subjects with native forearm AVFs (91 AVFs, located at the wrist; 29 AVFs, located at the midforearm). All AVFs underwent fistulography, which identified greater than 50% stenosis in 54 cases. RESULTS: Receiver operating characteristic curve analysis showed that dQa, Qa, and Qa/MAP have a high stenosis discriminative ability with similar areas under the curve (AUCs), ie, 0.961 +/- 0.025, 0.946 +/- 0.021, and 0.912 +/- 0.032, respectively. In the population as a whole, optimal thresholds for stenosis were Qa less than 750 mL/min alone and in combination with dQa greater than 25% (efficiency, 90%); however, the best threshold depended on anastomotic site; it was Qa less than 750 mL/min for an AVF at the wrist and Qa less than 1,000 mL/min for an AVF in the midforearm. Qa was the best predictor of incipient thrombosis (AUC, 0.981 +/- 0.013) with an optimal threshold at less than 300 mL/min (efficiency, 94%). Pooled intra-assay and interassay variation coefficients were 8.2% for MAP, 7.9% for Qa, and 11.2% for Qa/MAP. CONCLUSION: Our study shows that ultrasound dilution Qa measurement is a reproducible and highly accurate tool for detecting stenosis and predicting thrombosis in forearm AVFs. Neither Qa/MAP nor dQa improve the diagnostic performance of Qa alone, although its combination with dQa increases the test's sensitivity for stenosis

A prospective controlled trial on effect of percutaneous transluminal angioplast on functioning arteriovenous fistulae survival

Balloon angioplasty (PTA) is an established treatment modality for stenosis in dysfunctional arteriovenous fistulae (AVF), although most studies showing efficacy have been retrospective, uncontrolled, and nonrandomized. In addition, it is unknown whether correction of stenosis not associated with significant hemodynamic, functional, and clinical abnormality may improve survival in AVF. This study was a prospective controlled open trial to evaluate whether prophylactic PTA of stenosis not associated with access dysfunction improves survival in native, virgin, radiocephalic forearm AVF. Sixty-two stenotic, functioning AVF, i.e., able to provide adequate dialysis, were enrolled in the study: 30 were allocated to control and 32 to PTA. End points of the study were either AVF thrombosis or surgical revision due to reduction in delivered dialysis dose. Kaplan-Meier analysis showed that PTA improved AVF functional failure-free survival rates (P = 0.012) with a fourfold increase in median survival and a 2.87-fold decrease in risk of failure. Cox proportional hazard model identified PTA as the only variable associated with outcome (P = 0.012). PTA induced an increase in access blood flow rate (Qa) by 323 (236 to 445) ml/min (P < 0.001), suggesting that improved AVF survival is the result of increased Qa. PTA was also associated with a significant decrease in access-related morbidity by approximately halving the risk of hospitalization, central venous catheterization, and thrombectomy (P < 0.05). This study shows that prophylactic PTA of stenosis in functioning forearm AVF improves access survival and decreases access-related morbidity, supporting the usefulness of preventive correction of stenosis before the development of access dysfunction. It also strongly supports surveillance program for early detection of stenosis

The role of surveillance in mature arteriovenous fistula management.

The existing guidelines recommend arteriovenous fistulae (AVF) surveillance by access blood flow (Qa) measurement and the correction of hemodynamically significant stenoses to prolong access survival. Unfortunately, many studies supporting these recommendations are inadequate methodologically; therefore, both the optimal criteria for surveillance and the value of preventive stenosis repair in AVF remain controversial. Recent literature confirms that Qa measurement allows an accurate identification of both stenosis (area under the curve (AUC) ranging from 0.80-0.93) and access at risk of failure (AUC ranging from 0.82-0.98) in AVFs and suggests a Qa 25% as optimal predictors for stenosis and a Qa <400 ml/min for incipient thrombosis. Recent prospective studies evaluated whether Qa surveillance could improve AVF patency rates compared to monitoring based on clinical and dialysis-related criteria alone. The majority of studies have historical, rather than concurrent, control groups and provide conflicting results, some showing a reduction and some showing no change in thrombosis rates by Qa monitoring. On the other hand, the few randomized controlled studies available show that Qa surveillance, when coupled with preemptive intervention, reduces the already low thrombosis rate in AVF and suggest that the functional access life can be prolonged. However, there is still the need for additional methodologically adequate studies to understand fully the role of surveillance in AVF management

Stenosis of Brescia-Cimino fistula (AVF): Early diagnosis and results of angioplasty (PTA)

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Outcomes of the surgical revision of stenosed and thrombosed forearm arteriovenous fistulae for hemodialysis

Surgery is an established treatment for stenosed and thrombosed forearm arteriovenous fistulae (AVFs), but the literature concerning its outcome is limited. We report a 6-yr experience of the surgical repair of stenosis in patent and thrombosed forearm AVFs, and compare the outcome of two techniques, proximal neo-anastomosis (NEO) vs. replacement of the stenosed segment with a short PTFE interposition graft (Jump graft (JG))

Adding access blood flow surveillance to clinical monitoring reduces thrombosis rates and costs, and improves fistula patency in the short term: a controlled cohort study.

BACKGROUND: Access blood flow (Qa) measurement is the recommended method for fistula (AVF) surveillance for stenosis, but whether it may be beneficial and cost-effective is controversial. METHODS: We conducted a 5-year controlled cohort study to evaluate whether adding Qa surveillance to unsystematic clinical monitoring (combined with elective stenosis repair) reduces thrombosis and access loss rates, and costs in mature AVFs. We prospectively collected data in 159 haemodialysis patients with mature AVFs, 97 followed by unsystematic clinical monitoring (Control) and 62 by adding Qa surveillance to monitoring (Flow). Indications for imaging and stenosis repair were clinically evident access dysfunction in both groups and a Qa 20% in Flow. RESULTS: Adding Qa surveillance prompted an increase in access imaging (HR 2.96, 95% CI 1.79-4.91, P < 0.001), stenosis detection (HR 2.55, 95% CI 1.48-4.42, P = 0.001) and elective repair (HR 2.26, 95% CI 1.16-4.43, P = 0.017), and a reduction in thromboses (HR 0.27, 95% CI 0.09-0.79, P = 0.017), central venous catheter placements (HR 0.14, 95% CI 0.03-0.42, P = 0.010) and access losses (HR 0.35, 95% CI 0.11-1.09, P = 0.071). In the Kaplan-Meier analysis, adding Qa surveillance only extended short-term cumulative patency (P = 0.037 in the Breslow test). Mean access-related costs were 1213 Euro/AVF-year in Control and 743 in Flow (P < 0.001). CONCLUSIONS: Our controlled cohort study shows that adding Qa surveillance to monitoring in mature AVFs is associated with a better detection and elective treatment of stenosis, and lower thrombosis rates and access-related costs, although the cumulative access patency was only extended in the first 3 years after fistula maturation. We are aware of the limitations of our study (non-randomization and the possible centre effect) and that further, better-designed trials are needed to arrive at a definitive answer concerning the role of Qa surveillance for fistulae