Background: Early detection with elective intervention of malfunctioning arteriovenous (AV) grafts improves access viability. Herein, we evaluated outlet venous pressure (OP), normalized by mean arterial blood pressure (MABP), at varying blood flow (Qb) rates in the detection of venous outlet stenosis.
Methods: This single-center, observational study included stable dialysis patients with polytetrafluoroethylene (PTFE) AV grafts. Phase I involved the determination of the optimal Qb (0, 50, 250, or 400 mL/min) and threshold OP/MABP. Sixty-one patients were followed up for 6 months. The primary end point was graft thrombosis. Phase II assessed serial slow-flow pressure (SFpr = OP/MABP at Qb of 50 mL/min) in a larger sample size (N = 152). The primary end point was graft thrombosis. Phase III implemented the use of SFpr monitoring in the detection and correction of outlet lesion(s).
Results: In phase I, 21 patients developed graft thrombosis. The most significant difference in pressure between the functioning and thrombosed grafts was at Qb of 0 mL/min and SFpr. The threshold of OP/MABP at Qb 0 (>0.53) and SFpr (>0.6) were predictive of graft thrombosis. In phase II, 37 of 42 patients with graft thrombosis had SFpr>0.6 (sensitivity 88.1%; specificity 97.2%; positive and negative predictive values were 90.2% and 95.5%, respectively). In phase III, 13 patients with SFpr>0.6 had outlet lesions on angiography.
Conclusion: Serial SFpr used in conjunction with angiography and angioplasty provides a strategy for reducing the incidence of thrombosis. This technique has comparable sensitivity and specificity to other existing methods. This technique is both time-efficient and cost-effective.