title: Validation of the in vivo intravascular ultrasound measurement of in-stent neointimal hyperplasia volumes.
abstract: OBJECTIVE
  This study was undertaken to validate the in vivo intravascular ultrasound (IVUS) measurement of in-stent neointimal hyperplasia (IH) volumes.
  
  
  BACKGROUND
  Because stents reduce restenosis compared to balloon angioplasty, stent use has increased significantly. As a result, in-stent restenosis is now an important clinical problem. Serial IVUS studies have shown that in-stent restenosis is secondary to intimal hyperplasia. To evaluate strategies to reduce in-stent restenosis, accurate measurement of in-stent neointimal tissue is important.
  
  
  METHODS
  Using a porcine coronary artery model of in-stent restenosis, single Palmaz-Schatz stents were implanted into 16 animals with a stent:artery ratio of 1.3:1. Intravascular ultrasound imaging was performed at 1 month, immediately prior to animal sacrifice. In vivo IVUS and ex vivo histomorphometric measurements included stent, lumen and IH areas; IH volumes were calculated with Simpson's rule.
  
  
  RESULTS
  Intravascular ultrasound measurements of IH (30.4+/-11.0 mm3) volumes correlated strongly with histomorphometric measurements (26.7+/-8.5 mm3, r=0.965, p < 0.0001). The difference between the IVUS and the histomorphometric measurements of IVUS volume was 4.1+/-2.7 mm3 or 15.8+/-11% (standard error of the estimate=0.7). Both histomorphometry and IVUS showed that IH was concentric and uniformly distributed over the length of the stent. Intravascular ultrasound detected neointimal thickening of < or =0.2 mm in 5 of 16 stents. Sample size calculations based on the IVUS measurement of IH volumes showed that 12 stented lesions/arm would be required to show a 50% reduction in IVUS-measured IH volume and 44 stented lesions/arm would be required to show a 25% reduction in IH volume.
  
  
  CONCLUSIONS
  In vivo IVUS measurement of IH volumes correlated strongly with ex vivo histomorphometry. Using volumetric IVUS end points, small sample sizes should be necessary to demonstrate effectiveness of strategies to reduce in-stent restenosis.
authors.affiliation: Intravascular Ultrasound Imaging Laboratory, Washington Hospital Center, DC, USA.
authors.forename: R
authors.initials: R
authors.lastname: Mehran
authors.forename: G S
authors.initials: GS
authors.lastname: Mintz
authors.forename: M K
authors.initials: MK
authors.lastname: Hong
authors.forename: F O
authors.initials: FO
authors.lastname: Tio
authors.forename: O
authors.initials: O
authors.lastname: Bramwell
authors.forename: A
authors.initials: A
authors.lastname: Brahimi
authors.forename: K M
authors.initials: KM
authors.lastname: Kent
authors.forename: A D
authors.initials: AD
authors.lastname: Pichard
authors.forename: L F
authors.initials: LF
authors.lastname: Satler
authors.forename: J J
authors.initials: JJ
authors.lastname: Popma
authors.forename: M B
authors.initials: MB
authors.lastname: Leon
mesh_terms: D015906:Angioplasty, Balloon, Coronary / Q000295:instrumentation*; D000818:Animals; D003331:Coronary Vessels / Q000000981:diagnostic imaging; D005352:Fibromuscular Dysplasia / Q000000981:diagnostic imaging*; D012680:Sensitivity and Specificity; D015607:Stents; D013552:Swine; D017540:Tunica Media / Q000000981:diagnostic imaging; D018084:Ultrasonography, Interventional