title: Assessment of FFR-negative intermediate coronary artery stenoses by spectral analysis of the radiofrequency intravascular ultrasound signal.
abstract: BACKGROUND
  Assessing the clinical importance of angiographically intermediate coronary artery stenoses at the time of cardiac catheterization remains a challenge. Spectral analysis of radiofrequency ultrasound backscatter signals, or virtual histology (VH), allows in vivo assessment of plaque composition. This study characterizes the VH composition of fractional flow reserve (FFR)-negative intermediate stenoses and adjacent vessel segments.
  
  
  METHODS
  Intermediate coronary artery stenoses (> 40% and < 70% diameter stenosis) were assessed by pressure wire. If the FFR was > or = 0.75, percutaneous coronary intervention was deferred and VH was performed on the lesion and adjacent segments using a commercially available system. The primary clinical endpoint was any adverse cardiac event.
  
  
  RESULTS
  Thirty-seven intermediate stenoses in 30 patients were studied. The reference vessel size was 3.02 +/- 0.71 mm, the QCA diameter stenosis was 52 +/- 6% and the FFR was 0.89 +/- 0.07. The target stenoses were characterized by VH as: thin-cap fibroatheroma (VH-TCFA; n = 22); fibrous cap atheroma (n = 5), fibrocalcific lesion (n = 7) and pathological intimal thickening (n = 3). The relative contribution of each stenosis plaque component was conserved across adjacent segments ("signature" plaque). Three patients, all with VH-TCFAs at index, had events in the clinical follow-up period of 12 +/- 2 months, but only 1 of these patients had an event related to the index stenosis.
  
  
  CONCLUSIONS
  FFR-negative intermediate stenoses have heterogeneous plaque by VH, but are enriched in VH-TCFAs. Relative plaque composition is conserved along adjacent vessel segments. Although the specificity of VH-TCFA for index stenosis-related events appears low, larger trials are needed to assess the prognostic value of VH in this lesion subset.
authors.affiliation: U.C. Davis Medical Center, Division of Cardiovascular Medicine, 4860 Y Street, Suite #2820, Sacramento, CA 95817, USA. jason.rogers@ucdmc.ucdavis.edu
authors.forename: Jason H
authors.initials: JH
authors.lastname: Rogers
authors.forename: Jacob
authors.initials: J
authors.lastname: Wegelin
authors.forename: Kori
authors.initials: K
authors.lastname: Harder
authors.forename: Richard
authors.initials: R
authors.lastname: Valente
authors.forename: Reginald
authors.initials: R
authors.lastname: Low
mesh_terms: D000368:Aged; D003326:Coronary Circulation; D023921:Coronary Stenosis / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D011846:Radio Waves; D012542:Scattering, Radiation; D018084:Ultrasonography, Interventional