Value of static venous pressure for predicting arteriovenous graft thrombosis

Background. Static venous pressure elevation has been shown to have both high sensitivity and high specificity for hemodialysis arteriovenous (AV) graft venous anastomosis stenosis. However, it is not known how well static venous pressure elevation predicts subsequent AV graft thrombosis. Methods. Monthly static venous pressure measurements were made during two consecutive dialysis sessions in all patients with a functioning upper extremity AV graft in two hemodialysis units during a 16-month period. Static venous pressure was normalized to systolic blood pressure and corrected for the height difference between the AV graft and the dialysis machine pressure transducer to yield the static venous pressure ratio (SVPR). Results. Fifty-four patients (38%) had a thrombotic event during the study period and thus were labeled as clotters. Among the clotters, SVPR just prior to thrombosis was 0.51 +/- 0.16 (mean +/- SD), and mean time to thrombosis following an elevated SVPR (greater than or equal to0.4) was 118 +/- 106 days. Receiver operating characteristic (ROC) curves were generated using the sensitivities and specificities of a range of SVPR values for access thrombosis within one, two, three and four months. The areas under the curve (AUCs) for the ROC curves ranged from 0.557 to 0.638, reflecting the absence of SVPR values with both high sensitivity and high specificity for access thrombosis. An increase in SVPR over time was not a better predictor of access thrombosis than absolute SVPR. Conclusion. Static venous pressure measurement is not an optimal screening test for identifying AV grafts at risk for thrombosis.