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Screening for hemodialysis graft stenosis and short-term thrombosis risk: A comparison of the available tools
Nicola Tessitore1, Giovanni Lipari2, Alberto Contro3
1Hemodialysis Borgo Roma, Nephrology and Dialysis Unit, Department of Medicine, Azienda Ospedaliera Universitaria Integrata Verona, Verona, Italy.
Insights
Hemodialysis graft screening can effectively monitor access blood flow (Qa) to detect stenosis and predict thrombosis risk. Avoiding acute hypotension and intervening at specific Qa thresholds can help prevent graft thrombosis.
Area of Science:
- Nephrology
- Vascular Surgery
- Radiology
Background:
- Current guidelines recommend hemodialysis graft screening for significant stenosis (>50%) to prevent thrombosis.
- However, insufficient evidence exists to favor one screening tool over others due to a lack of comparative studies.
Purpose of the Study:
- To compare the diagnostic performance of all available screening tools for hemodialysis grafts.
- To identify the optimal screening approach for detecting significant stenosis and predicting short-term thrombosis.
Main Methods:
- A comparative study involving 62 grafts.
- Performance evaluation of duplex ultrasound (stenosis detection - StD, access blood flow - QaD), ultrasound dilution access blood flow (QaU), venous intra-access pressure ratio (VAPR), and dynamic pressure measurements.
- Diagnosis of significant stenosis (StA) via angiography and prediction of thrombosis within 4 months.
- Recording of thrombotic events and symptomatic acute hypotension.
Main Results:
- VAPR > 0.70 and QaU < 1600 mL/min best identified significant stenosis (91% sensitivity).
- QaU < 1000 mL/min or StD offered high positive predictive values (95%-93%) for avoiding unnecessary angiograms.
- Significant thrombosis predictors included acute hypotension episodes and reduced access blood flow (QaU or QaD).
- Thrombosis risk increased significantly at QaU < 1000 mL/min or QaD < 1300 mL/min, even after adjusting for hypotension.
Conclusions:
- Access blood flow (Qa) surveillance alone is effective for screening hemodialysis graft stenosis and short-term thrombosis risk.
- Avoiding acute hypotension and correcting stenosis at specific Qa thresholds (QaU < 1000 mL/min or QaD < 1300 mL/min) can mitigate thrombosis risk.
Introduction:
Guidelines recommend hemodialysis graft screening to identify and repair significant (>50%) stenosis at high risk of thrombosis, but there is insufficient evidence to prefer one or other screening tool due to the lack of studies comparing all available options.
Methods:
Seeking an optimal screening approach, we compared the performance of all currently used tools (duplex ultrasound to detect significant stenosis (StD) and measure access blood flow (QaD), ultrasound dilution access blood flow (QaU), static venous intra-access pressure ratio (VAPR), dynamic arterial and venous pressures measurement, and monitoring) for diagnosing significant angiography-proven stenosis (StA) and predicting incipient thrombosis (occurring within 4 months) in 62 grafts. All thrombotic and symptomatic acute hypotension episodes were recorded during follow-up.
Results:
VAPR > 0.70 and QaU < 1600 mL/min were the best indicators to angiography for those aiming to identify the majority of StA (91% sensitivity) and QaU < 1000 mL/min or StD for those aiming to avoid unnecessary angiograms (95%-93% positive predictive value). At Cox's analysis, the only significant thrombosis predictors were acute hypotension episodes (relative risk = 4.4 (95% confidence interval = 2.2-8.8), p < 0.0001) and QaU or QaD (14% (95% confidence interval = 8-21) or 16% (95% confidence interval = 6-25) increased risk per 100 mL/min drop in Qa, p < 0.003). Thrombosis risk (adjusted for acute hypotension) became significantly higher at QaU = 1000-700 mL/min (relative risk = 3.6 (95% confidence interval = 1.6-8.2), p < 0.001) and QaD = 1300-1000 mL/min (relative risk = 3.1 (95% confidence interval = 1.1-12.8), p = 0.031). The proportion of thromboses attributable to acute hypotension was 40% (95% confidence interval = 24-57).
Conclusions:
Our comparative study showed that an effective screening for graft stenosis and short-term thrombosis risk can rely on Qa surveillance alone, and suggested that avoiding acute hypotension and correcting stenosis at QaU < 1000 mL/min or QaD < 1300 mL/min can contain thrombosis risk.
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