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Relationship between vascular access flow and hemodynamically significant stenoses in arteriovenous grafts
Nikolai M Krivitski1, Swaroop Gantela
1Transonic Systems, Inc., Ithaca, New York, U.S.A. nikolai.krivitski@transonic.com
Insights
Vascular access flow monitoring for hemodialysis patients can be improved. A decrease of 20-30% in graft flow indicates significant stenosis, and higher thresholds may enhance surveillance accuracy for upper arm grafts.
Area of Science:
- Nephrology
- Vascular Surgery
- Biomedical Engineering
Background:
- Vascular access dysfunction is a significant cause of morbidity in hemodialysis patients.
- National Kidney Foundation K/DOQI Guidelines recommend access flow monitoring for surveillance.
- Established K/DOQI thresholds include an absolute 600 ml/min and a dynamic threshold of <1000 ml/min with >25% decrease over 4 months.
Purpose of the Study:
- To evaluate the application of NKF K/DOQI access flow guidelines.
- To assess the hemodynamic significance of stenosis based on flow criteria.
- To optimize surveillance strategies for hemodialysis access.
Main Methods:
- Analysis of human and animal experimental data.
- Development and application of a mathematical model for arteriovenous graft systems.
- Evaluation of K/DOQI thresholds against experimental and modeled data.
Main Results:
- A decrease of 20-30% or more in graft flow generally indicates hemodynamically significant stenosis.
- The mathematical model indicates that not all 50-60% stenoses are hemodynamically significant.
- Increasing the dynamic K/DOQI threshold to 1200 ml/min may improve surveillance for high-flow upper arm grafts.
Conclusions:
- Access flow monitoring is crucial for detecting hemodialysis vascular access dysfunction.
- The K/DOQI dynamic threshold may require adjustment for specific graft types and locations.
- Optimized surveillance thresholds can enhance the predictive value of access monitoring.
Background:
Vascular access dysfunction is a major source of hemodialysis patient morbidity. The NKF K/DOQI Guidelines promote access flow monitoring as the most preferred access surveillance method and have established access flow thresholds for fistulography: an absolute threshold of 600 ml/min and a dynamic threshold of flow less than 1000 ml/min that has decreased by more than 25% over 4 months. The Guidelines apply universally to accesses of different types, sizes, locations, and initial flow rates.
Methods:
This article studies the application of access flow guidelines with human experimental data, animal experimental data, and a mathematical model of the arteriovenous graft system.
Results And Conclusions:
Analysis of experimental data and the mathematical model shows that a 20 to 30% and greater decrease in graft flow generally suggests the appearance of hemodynamically significant stenosis as defined by flow criteria. The model suggests that not all 50 to 60% stenoses may be hemodynamically significant or the most flow limiting. The mathematical model also suggests that positive predictive value of access surveillance may be increased for high-flow upper arm grafts by increasing the dynamic K/DOQI threshold from 1000 ml/min to 1200 ml/min.
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