Relationship between vascular access flow and hemodynamically significant stenoses in arteriovenous grafts

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.

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.

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.