title: SPY technology as an adjunctive measure for lower extremity perfusion.
abstract: OBJECTIVE
  Lack of a reliable outcome measure often leads to excessive or insufficient interventions for critical limb ischemia (CLI). SPY technology (Novadaq Technologies Inc, Bonita Springs, Fla), widely adapted by plastic and general surgeons, uses laser-assisted fluorescence angiography (LAFA) to assess tissue perfusion. We sought to determine the role of SPY as an alternative, perhaps more reliable outcome measure for vascular interventions.
  
  
  METHODS
  All patients undergoing elective or urgent revascularization for claudication and CLI were prospectively recruited from June 2012 to August 2014. LAFA using SPY technology was performed before and after revascularization procedures under a standard Institutional Review Board-approved protocol. Quantitative measures of perfusion at plantar surfaces were analyzed and compared with ankle-brachial index.
  
  
  RESULTS
  A total of 93 patients with claudication or CLI underwent LAFA before and after a revascularization procedure in the study period. The mean preoperative ankle-brachial index increased from 0.60 to 0.84 (P < .001) after a revascularization procedure. Plantar perfusion as measured by LAFA also improved significantly after intervention. Ingress, defined as the rate at which fluorescence intensity increases on the plantar surface during LAFA, increased from 7.1 to 12.4 units/s (P < .001). Peak perfusion, defined as the difference between the baseline and the peak of fluorescence intensity, increased from 97.1 and 143.9 units (P < .001). Egress, defined as the rate at which intensity diminishes after reaching peak perfusion, increased from 1.0 to 1.9 units/s (P = .035). Procedure-related digital embolization was also observed in several patients despite lack of an angiographic finding.
  
  
  CONCLUSIONS
  This is the largest prospective study evaluating SPY technology in peripheral vascular interventions. Our study shows that SPY is a valuable tool in visualizing real-time procedural outcomes and providing additionally useful information on regional tissue perfusion. Further investigation is warranted to standardize outpatient use and to determine threshold values that predict wound healing.
authors.affiliation: Division of Vascular Surgery, Stanford University, Palo Alto, Calif.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Colvard
authors.affiliation: Division of Vascular Surgery, Stanford University, Palo Alto, Calif.
authors.forename: Nathan K
authors.initials: NK
authors.lastname: Itoga
authors.affiliation: Section of Vascular Surgery, VA Palo Alto Health Care System, Palo Alto, Calif.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Hitchner
authors.affiliation: Department of Vascular Surgery, The First Affiliated Hospital, Harbin Medical University, Harbin, China.
authors.forename: Qingfeng
authors.initials: Q
authors.lastname: Sun
authors.affiliation: Division of Vascular Surgery, Stanford University, Palo Alto, Calif; Section of Vascular Surgery, VA Palo Alto Health Care System, Palo Alto, Calif.
authors.forename: Becky
authors.initials: B
authors.lastname: Long
authors.affiliation: Division of Vascular Surgery, Stanford University, Palo Alto, Calif; Section of Vascular Surgery, VA Palo Alto Health Care System, Palo Alto, Calif.
authors.forename: George
authors.initials: G
authors.lastname: Lee
authors.affiliation: Division of Vascular Surgery, Stanford University, Palo Alto, Calif.
authors.forename: Venita
authors.initials: V
authors.lastname: Chandra
authors.affiliation: Division of Vascular Surgery, Stanford University, Palo Alto, Calif; Section of Vascular Surgery, VA Palo Alto Health Care System, Palo Alto, Calif. Electronic address: weizhou@stanford.edu.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhou
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D055109:Ankle Brachial Index; D001783:Blood Flow Velocity; D016638:Critical Illness; D004617:Embolism / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D005260:Female; D005451:Fluorescein Angiography / Q000295:instrumentation*; D005456:Fluorescent Dyes / Q000008:administration & dosage*; D006801:Humans; D007208:Indocyanine Green / Q000008:administration & dosage*; D007275:Injections, Intravenous; D007383:Intermittent Claudication / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy; D007511:Ischemia / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy; D007834:Lasers; D035002:Lower Extremity / Q000098:blood supply*; D008297:Male; D008875:Middle Aged; D055420:Perfusion Imaging / Q000295:instrumentation* / Q000379:methods*; D058729:Peripheral Arterial Disease / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012039:Regional Blood Flow; D015203:Reproducibility of Results; D013997:Time Factors; D016896:Treatment Outcome; D014654:Vascular Patency
chemical_list: D005456:Fluorescent Dyes; D007208:Indocyanine Green