title: Quantitative analysis of intraventricular dyssynchrony using wall thickness by multidetector computed tomography.
abstract: OBJECTIVE
  We sought to determine the feasibility of cardiac computed tomography (CT) to detect significant differences in the extent of left ventricular dyssynchrony in heart failure (HF) patients with wide QRS, HF patients with narrow QRS, and age-matched controls.
  
  
  BACKGROUND
  The degree of mechanical dyssynchrony has been suggested as a predictor of response to cardiac resynchronization therapy. There have been no published reports of dyssynchrony assessment with the use of CT.
  
  
  METHODS
  Thirty-eight subjects underwent electrocardiogram-gated contrast-enhanced 64-slice multidetector CT. The left ventricular endocardial and epicardial boundaries were delineated from short-axis images reconstructed at 10% phase increments of the cardiac cycle. Global and segmental CT dyssynchrony metrics that used changes in wall thickness, wall motion, and volume over time were assessed for reproducibility. We defined a global metric using changes in wall thickness as the dyssynchrony index (DI).
  
  
  RESULTS
  The DI was the most reproducible metric (interobserver and intraobserver intraclass correlation coefficients >/=0.94, p < 0.0001) and was used to determine differences between the 3 groups: HF-wide QRS group (ejection fraction [EF] 22 +/- 8%, QRS 163 +/- 28 ms), HF-narrow QRS (EF 26 +/- 7%, QRS 96 +/- 11 ms), and age-matched control subjects (EF 64 +/- 5%, QRS 87 +/- 9 ms). Mean DI was significantly different between the 3 groups (HF-wide QRS: 152 +/- 44 ms, HF-narrow QRS: 121 +/- 58 ms, and control subjects: 65 +/- 12 ms; p < 0.0001) and greater in the HF-wide QRS (p < 0.0001) and HF-narrow QRS (p = 0.005) groups compared with control subjects. We found that DI had a good correlation with 2-dimensional (r = 0.65, p = 0.012) and 3-dimensional (r = 0.68, p = 0.008) echocardiographic dyssynchrony.
  
  
  CONCLUSIONS
  Quantitative assessment of global CT-derived DI, based on changes in wall thickness over time, is highly reproducible and renders significant differences between subjects most likely to have dyssynchrony and age-matched control subjects.
authors.affiliation: Cardiac MR PET CT Program, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA. qtruong@partners.org
authors.forename: Quynh A
authors.initials: QA
authors.lastname: Truong
authors.forename: Jagmeet P
authors.initials: JP
authors.lastname: Singh
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Cannon
authors.forename: Ammar
authors.initials: A
authors.lastname: Sarwar
authors.forename: Khurram
authors.initials: K
authors.lastname: Nasir
authors.forename: Angelo
authors.initials: A
authors.lastname: Auricchio
authors.forename: Francesco F
authors.initials: FF
authors.lastname: Faletra
authors.forename: Antonio
authors.initials: A
authors.lastname: Sorgente
authors.forename: Cristina
authors.initials: C
authors.lastname: Conca
authors.forename: Tiziano
authors.initials: T
authors.lastname: Moccetti
authors.forename: Mark
authors.initials: M
authors.lastname: Handschumacher
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Brady
authors.forename: Udo
authors.initials: U
authors.lastname: Hoffmann
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D019560:Echocardiography, Three-Dimensional; D004562:Electrocardiography; D005240:Feasibility Studies; D005260:Female; D006333:Heart Failure / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011237:Predictive Value of Tests; D011857:Radiographic Image Interpretation, Computer-Assisted; D015203:Reproducibility of Results; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000503:physiopathology; D016277:Ventricular Function, Left