title: Applying harmonic optical microscopy for spatial alignment of atrial collagen fibers.
abstract: BACKGROUND
  Atrial fibrosis creates a vulnerable tissue for atrial fibrillation (AF), but the spatial disarray of collagen fibers underlying atrial fibrosis is not fully elucidated.
  
  
  OBJECTIVE
  This study hypothesizes that harmonics optical microscopy can illuminate the spatial mal-alignment of collagen fibers in AF via a layer-by-layer approach.
  
  
  METHODS
  Atrial tissues taken from patients who underwent open-heart surgery were examined by harmonics optical microscopy. Using the two-dimensional Fourier transformation method, a spectral-energy description of image texture was constituted and its entropy was used to quantify the mal-alignment of collagen fibers. The amount of collagen fiber was derived from its area ratio to total atrial tissue in each image. Serum C-terminal pro-collagen pro-peptide (CICP), pro-matrix metalloproteinase-1 (pro-MMP-1), and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) were also evaluated.
  
  
  RESULTS
  46 patients were evaluated, including 20 with normal sinus rhythm and 26 with AF. The entropy of spectral-energy distribution of collagen alignment was significantly higher in AF than that in sinus rhythm (3.97 ± 0.33 vs. 2.80 ± 0.18, p<0.005). This difference was more significant in the permanent AF group. The amount of collagen was also significantly higher in AF patients (0.39 ± 0.13 vs. 0.18 ± 0.06, p<0.005) but serum markers of cardiac fibrosis were not significantly different between the two groups.
  
  
  CONCLUSIONS
  Harmonics optical microscopy can quantify the spatial mal-alignment of collagen fibers in AF. The entropy of spectral-energy distribution of collagen alignment is a potential tool for research in atrial remodeling.
authors.affiliation: Division of Cardiology, Department of Internal Medicine, Far-Eastern Memorial Hospital, Taipei, Taiwan.
authors.forename: Yu-Wei
authors.initials: YW
authors.lastname: Chiu
authors.forename: Men Tzung
authors.initials: MT
authors.lastname: Lo
authors.forename: Ming-Rung
authors.initials: MR
authors.lastname: Tsai
authors.forename: Yi-Chung
authors.initials: YC
authors.lastname: Chang
authors.forename: Rong-Bin
authors.initials: RB
authors.lastname: Hsu
authors.forename: Hsu-Yu
authors.initials: HY
authors.lastname: Yu
authors.forename: Chi-Kuang
authors.initials: CK
authors.lastname: Sun
authors.forename: Yi-Lwun
authors.initials: YL
authors.lastname: Ho
mesh_terms: D000368:Aged; D000465:Algorithms; D001281:Atrial Fibrillation / Q000097:blood / Q000378:metabolism* / Q000473:pathology; D015415:Biomarkers / Q000097:blood; D024042:Collagen Type I / Q000097:blood / Q000737:chemistry / Q000378:metabolism*; D019277:Entropy; D005260:Female; D005355:Fibrosis; D006325:Heart Atria / Q000378:metabolism / Q000473:pathology; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D020781:Matrix Metalloproteinase 1 / Q000097:blood; D008853:Microscopy / Q000295:instrumentation / Q000379:methods*; D018613:Microscopy, Confocal / Q000295:instrumentation / Q000379:methods; D008875:Middle Aged; D010446:Peptide Fragments / Q000097:blood; D011347:Procollagen / Q000097:blood; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000097:blood
chemical_list: D015415:Biomarkers; D024042:Collagen Type I; D010446:Peptide Fragments; D011347:Procollagen; D019715:Tissue Inhibitor of Metalloproteinase-1; C042813:procollagen type I carboxy terminal peptide; D020781:Matrix Metalloproteinase 1