title: A new method of intraoperative hydraulic impedance measurement provides valuable prognostic information about infrainguinal graft patency.
abstract: OBJECTIVE
  Prognostic information about graft outcome, obtained by using a new method for intraoperative measurement of vascular impedance, was evaluated.
  
  
  METHODS
  Hydraulic impedance was measured in 136 infrainguinal bypass grafts that were entered into a multicenter trial. Seventy femoropopliteal and 66 femorocrural polytetrafluoroethylene (PTFE) grafts were used. The arterial impedance measurement involved a silicon bypass graft temporarily inserted between the proximal and distal anastomoses sites. A flowmeter probe and a pressure transducer were incorporated into the tube. The digitally stored waveforms were subjected to a fast Fourier transformation and both input (Z(x)) and characteristic (Z(0)) impedances, as well as phase relations, were computed and related to graft outcome after 3 years.
  
  
  RESULTS
  Significant prognostic information for both popliteal and crural grafts was provided by means of the phase angle of the first harmonic. Primary and secondary patency rates for popliteal bypasses were 45% +/- 1% and 65% +/- 2% for phase angles greater than -40 degrees (n = 57) and 37% +/- 1% and 40% +/- 1% for phase angles less than -40 degrees (n = 13, p(prim ) = not significant, p(sec) < 0.01). For crural grafts, the secondary patency rates were 49% +/- 1% and 61% +/- 2% for phase angles greater than -40 degrees (n = 53) and 15% +/- 1% and 0% for phase angles less than -40 degrees (n = 13, P <.01). All crural bypass grafts with phase angles less than -40 degrees occluded within 16 months. Steady flow resistance, as well as Z(x) and Z(0), failed to indicate a significant relation to graft prognosis.
  
  
  CONCLUSIONS
  This method provides reliable prognostic information regarding graft patency and opens hydraulic impedance measurement to clinical surgery. The phase lag between flow and pressure curves, as expressed by the phase angle of the first harmonic, provides significant prognostic information.
authors.affiliation: Department of Surgery, Charité, Humboldt-University Berlin, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Heise
authors.forename: U
authors.initials: U
authors.lastname: Krüger
authors.forename: U
authors.initials: U
authors.lastname: Settmacher
authors.forename: S
authors.initials: S
authors.lastname: Sklenar
authors.forename: P
authors.initials: P
authors.lastname: Neuhaus
authors.forename: H
authors.initials: H
authors.lastname: Scholz
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001157:Arterial Occlusive Diseases / Q000503:physiopathology / Q000601:surgery*; D001807:Blood Vessel Prosthesis; D019917:Blood Vessel Prosthesis Implantation; D005112:Extracorporeal Circulation; D005260:Female; D005263:Femoral Artery / Q000601:surgery; D006439:Hemodynamics; D006801:Humans; D007264:Inguinal Canal; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D010992:Plethysmography, Impedance / Q000295:instrumentation / Q000379:methods*; D011138:Polytetrafluoroethylene; D011150:Popliteal Artery / Q000601:surgery; D011379:Prognosis; D013997:Time Factors; D016896:Treatment Outcome; D014654:Vascular Patency; D014655:Vascular Resistance
chemical_list: D011138:Polytetrafluoroethylene