Two patients were referred for venography by vascular surgery consultants for various indications independent of flow criteria (AV fistula aneurysm evaluation, pseudo aneurysm evaluation) independent of the study. In addition following completion of the study, seven patients (3 AVF and 4 AVG) were evaluated with biplanar venography for nonflow indications (access pain, bleeding post-needle removal, difficult fistula cannulation). There was one significant (50%) stenosis detected in these nine patients. PTA of this stenosis had no effect on access flow.
There was a total of 35 PTA (successful and unsuccessful) during the study. There were 15 primary, 11 secondary, and 2 tertiary PTAs in patients with AV grafts. There were six primary and one secondary PTA in the AVF group. Failure to increase flow by 20% post-PTA defined failure of PTA. This occurred in 14% of fistula PTA attempts (1 of 7 PTA) and in 21% of AV graft (6 of 28 PTA). Access flow results pre- and post-PTA are graphically represented in Figure 1. All PTA attempts are recorded in this figure, including those deemed successful and unsuccessful. Flow at the end of the study for all access that were still patent is also shown Figure 1. These end-study data represent all patients and include those with and without an intervention.
Mean time from first to second PTA was 5.8 months in AV grafts. This could not be calculated for AVFs because there was only one repeat intervention. Mean follow-up post-PTA for AVF stood at 11.4 months at study closure. Three patients (3 of 7 PTA failures) deferred surgical revision, as described later in this article. Elective surgical revisions occurred in four patients, all with AV grafts. Mean increase in flow post-surgical revision was 655 ± 88 to 891 ± 136 mL/min (P < 0.05).
During the study period that encompassed 64 patient-years of hemodialysis, there were 10 episodes of thrombosis Table 1; this calculates to a total thrombosis rate of 0.156 or on average 16% per patient-year. The thrombosis rate per patient-year of hemodialysis for AVF was considerable less than for AV grafts (0.216, AVG vs. 0.074, AVF; P < 0.05). Eight of the 10 thromboses were predicted in that they occurred in patients who had an unsuccessful PTA and who were unwilling to undergo elective surgical revision or in whom a fistulogram was recommended and who postponed or canceled their fistulogram appointment (AV grafts thrombosed within 4 months of diminished flow, AV fistulae within 1 year of diminished flow). Two thromboses occurred in patients in whom access flow did not detect a significant drop in flow. Their previous access history did not appear different from the group as a whole.