Stenosis detection in forearm hemodialysis arteriovenous fistulae by multiphase contrast-enhanced magnetic resonance angiography: preliminary experience

Abstract

Purpose: To assess the feasibility and accuracy of multiphase contrast-enhanced magnetic resonance angiography (CE-MRA) in patients with dysfunctioning hemodialysis arteriovenous fistulae (AVF), using digital subtraction angiography (DSA) as the standard of reference.

Materials and methods: Fifteen patients with dysfunctioning AVF (eight radiocephalic and seven graft AVF) underwent CE-MRA. Dysfunction was defined as a flow decline of more than 25% in 1 month measured by dilutional flow measurements. CE-MRA was performed during injection of 35 mL of gadolinium-DTPA. The CE-MRA sequence consisted of a time-resolved series of 10 scans, each lasting approximately 10 seconds. The technical parameters were TR/TE/FA/voxel = 5.4/1.6/40/3.1 mm(3), and a rectangular surface reception coil was used. All patients were scheduled to undergo DSA at which an intervention was carried out when a stenosis >or=50% was seen. Two observers, unaware of each other's findings and the findings at DSA, quantified the number and degree of stenosis in the failing AVF. Image quality for CE-MRA and DSA was scored on a 3-point scale. The diagnostic performance of CE-MRA was analyzed with receiver-operator characteristic (ROC) analysis.

Results: CE-MRA and DSA examinations were performed without side effects in all 15 patients. Image quality was scored significantly better on CE-MRA (observer 1: CE-MRA, 2.0; DSA, 1.3; P =.001; observer 2: CE-MRA, 2.0; DSA, 1.4; P =.002). Interobserver agreement for detection of >or=50% stenosis was 0.81 (95% confidence interval (CI) = 0.71-0.92) for CE-MRA and 0.69 (95% CI = 0.55-0.84) for DSA. ROC analysis revealed a mean area under the curve of 0.78. On the patient level, at the >or=50% threshold, mean sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 100% (95% CI = 69%-100%), 10% (95% CI = 0%-78%), 70% (95% CI = 38%-92%), and 100% (95% CI = 50%-100%), respectively. At the >or=75% threshold, mean sensitivity, specificity, PPV, and NPV were 75% (95% CI = 20%-99%), 78% (95% CI = 39%-98%), 55% (95% CI = 12%-96%), and 89% (95% CI = 52%-100%), respectively.

Conclusion: CE-MRA is a useful diagnostic tool for detecting stenoses in flow-declined hemodialysis AVF prior to interventional DSA.