title: Magnetic resonance angiography in the follow-up of distal lower-extremity bypass surgery: comparison with duplex ultrasound and digital subtraction angiography.
abstract: OBJECTIVE
  The danger of limb loss as a consequence of acute occlusion of infrapopliteal bypasses underscores the requirement for careful patient follow-up. The objective of this study was to determine the agreement and accuracy of contrast material-enhanced moving-table magnetic resonance (MR) angiography and duplex ultrasonography (US) in the assessment of failing bypass grafts. In cases of discrepancy, digital subtraction angiography (DSA) served as the reference standard.
  
  
  METHODS
  MR angiography was performed in 24 consecutive patients with 26 femorotibial or femoropedal bypass grafts. Each revascularized limb was divided into five segments--(i) native arteries proximal to the graft; (ii) proximal anastomosis; (iii) graft course; (iv) distal anastomosis; and (v) native arteries distal to the graft-resulting in 130 vascular segments. Three readers evaluated all MR angiograms for image quality and the presence of failing grafts. The degree of stenosis was compared to the findings of duplex US, and in case of discrepancy, to DSA findings. Two separate analyses were performed with use of DSA only and a combined diagnostic endpoint as the reference standard.
  
  
  RESULTS
  Image quality was rated excellent or intermediate in 119 of 130 vascular segments (92%). Venous overlay was encountered in 26 of 130 segments (20%). In only two segments was evaluation of the outflow region not feasible. One hundred seventeen of 130 vascular segments were available for quantitative analysis. In 109 of 117 segments (93%), MR angiography and duplex US showed concordant findings. In the eight discordant segments in seven patients, duplex US overlooked four high-grade stenoses that were correctly identified by MR angiography and confirmed by DSA. Percutaneous transluminal angioplasty was performed in these cases. In no case did MR angiography miss an area of stenosis of sufficient severity to require treatment. Total accuracy for duplex US ranged from 0.90 to 0.97 depending on the reference standard used, whereas MR angiography was completely accurate (1.00) regardless of the standard definition.
  
  
  CONCLUSIONS
  Our data strongly suggest that the accuracy of MR angiography for identifying failing grafts in the infrapopliteal circulation is equal to that of duplex US and superior to that of duplex US in cases of complex revascularization. MR angiography should be included in routine follow-up of patients undergoing infrapopliteal bypass surgery.
authors.affiliation: Institute for Clinical Radiology, Ludwig-Maximilians-University, Marchioninistr. 15, 81377 Munich, Germany. oliver.meissner@med.uni-muenchen.de
authors.forename: Oliver A
authors.initials: OA
authors.lastname: Meissner
authors.forename: Frauke
authors.initials: F
authors.lastname: Verrel
authors.forename: Federico
authors.initials: F
authors.lastname: Tató
authors.forename: Uwe
authors.initials: U
authors.lastname: Siebert
authors.forename: Heldin
authors.initials: H
authors.lastname: Ramirez
authors.forename: Volker
authors.initials: V
authors.lastname: Ruppert
authors.forename: Stefan O
authors.initials: SO
authors.lastname: Schoenberg
authors.forename: Maximilian
authors.initials: M
authors.lastname: Reiser
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015901:Angiography, Digital Subtraction / Q000379:methods*; D001157:Arterial Occlusive Diseases / Q000601:surgery*; D019917:Blood Vessel Prosthesis Implantation / Q000009:adverse effects*; D003287:Contrast Media / Q000008:administration & dosage; D004868:Equipment Failure; D005260:Female; D005500:Follow-Up Studies; D006083:Graft Occlusion, Vascular / Q000175:diagnosis; D006801:Humans; D035002:Lower Extremity / Q000098:blood supply* / Q000601:surgery; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011446:Prospective Studies; D015203:Reproducibility of Results; D018616:Ultrasonography, Doppler, Duplex / Q000379:methods*; D014654:Vascular Patency / Q000502:physiology
chemical_list: D003287:Contrast Media