Aims: Low access flow and the diagnosis of high degrees of venous stenosis have been recommended as indications for prophylactic angioplasty. However, recent studies have shown that prophylactic angioplasty for > 50% stenosis did not prolong graft patency, and that a single flow measurement may not accurately predict graft failure. In this study we compared the value of monthly measurement of access flow and of the maximal degree of stenosis in the detection of graft failure over a three-month period.
Methods: Thirty-nine hemodialysis patients with polytetrafluoroethylene (PTFE) grafts were evaluated by Doppler ultrasound at monthly intervals for three months. Graft failures were defined as thrombosis, or surgical and angioplastic revisions required because of the presence of access recirculation, and patients with graft failure were followed within the subsequent one-month periods of observation.
Results: Twelve graft failures occurred during the three-month period of observation. The risk for subsequent graft failure significantly increased at flows < 300 ml/min. Nine (20%) graft failures occurred with stenoses of 30 to 50%, and three (13%) with stenoses of> 50%. The grafts that failed in the second and the third study months had a 25.8% (380 +/- 62 vs. 287 +/- 190 ml/min, p < 0.05) and a 36.5% (393 +/- 142 vs. 226 +/- 41 ml/min, p < 0.05) decrease in access flow, respectively. There was no significant change in access flow for the grafts patent throughout the study (911 +/- 333, 794 +/- 302, and 919 +/383 ml/min, p = ns). No significant increases in maximal stenosis were found for the grafts that failed in the second month (44 +/- 6.1 vs. 48 +/- 15%, p = ns) and the third month (48 +/- 9 vs. 51 +/- 16%, p = ns). There were no significant changes in the maximum stenosis for the grafts patent throughout the three-month study periods (37 +/- 15,43 +/- 11, and 44 +/- 15%, p = ns).
Conclusions: Access flow is a more sensitive predictor of graft failure than stenosis. Examination of trend in decline of access flow is a more powerful indicator to detect graft dysfunction than an individual single flow value.