title: Reproducibility of in-vivo diffusion tensor cardiovascular magnetic resonance in hypertrophic cardiomyopathy.
abstract: BACKGROUND
  Myocardial disarray is an important histological feature of hypertrophic cardiomyopathy (HCM) which has been studied post-mortem, but its in-vivo prevalence and extent is unknown. Cardiac Diffusion Tensor Imaging (cDTI) provides information on mean intravoxel myocyte orientation and potentially myocardial disarray. Recent technical advances have improved in-vivo cDTI, and the aim of this study was to assess the interstudy reproducibility of quantitative in-vivo cDTI in patients with HCM.
  
  
  RESULTS
  A stimulated-echo single-shot-EPI sequence with zonal excitation and parallel imaging was implemented. Ten patients with HCM were each scanned on 2 different days. For each scan 3 short axis mid-ventricular slices were acquired with cDTI at end systole. Fractional anisotropy (FA), mean diffusivity (MD), and helix angle (HA) maps were created using a cDTI post-processing platform developed in-house. The mean ± SD global FA was 0.613 ± 0.044, MD was 0.750 ± 0.154 × 10-3 mm2/s and HA was epicardium -34.3 ± 7.6°, mesocardium 3.5 ± 6.9° and endocardium 38.9 ± 8.1°. Comparison of initial and repeat studies showed global interstudy reproducibility for FA (SD = ± 0.045, Coefficient of Variation (CoV) = 7.2%), MD (SD = ± 0.135 × 10-3 mm2/s, CoV = 18.6%) and HA (epicardium SD = ± 4.8°; mesocardium SD = ± 3.4°; endocardium SD = ± 2.9°). Reproducibility of FA was superior to MD (p = 0.003). MD was significantly higher in the septum than the reference lateral wall (0.784 ±0.188 vs 0.714 ±0.155 ×10-3 mm2/s, p <0.001) [corrected]. Septal HA was significantly lower than the reference lateral wall in all 3 transmural layers (from -8.3° to -10.4°, all p < 0.001).
  
  
  CONCLUSIONS
  To the best of our knowledge, this is the first study to assess the interstudy reproducibility of DTI in the human HCM heart in-vivo and the largest cDTI study in HCM to date. Our results show good reproducibility of FA, MD and HA which indicates that current technology yields robust in-vivo measurements that have potential clinical value. The interpretation of regional differences in the septum requires further investigation.
authors.affiliation: Cardiovascular Magnetic Resonance Unit, Royal Brompton Hospital, Sydney Street, London SW3 6NP, United Kingdom.
authors.forename: Laura-Ann
authors.initials: LA
authors.lastname: McGill
authors.forename: Tevfik F
authors.initials: TF
authors.lastname: Ismail
authors.forename: Sonia
authors.initials: S
authors.lastname: Nielles-Vallespin
authors.forename: Pedro
authors.initials: P
authors.lastname: Ferreira
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Scott
authors.forename: Michael
authors.initials: M
authors.lastname: Roughton
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Kilner
authors.forename: S Yen
authors.initials: SY
authors.lastname: Ho
authors.forename: Karen P
authors.initials: KP
authors.lastname: McCarthy
authors.forename: Peter D
authors.initials: PD
authors.lastname: Gatehouse
authors.forename: Ranil
authors.initials: R
authors.lastname: de Silva
authors.forename: Peter
authors.initials: P
authors.lastname: Speier
authors.forename: Thorsten
authors.initials: T
authors.lastname: Feiweier
authors.forename: Choukkri
authors.initials: C
authors.lastname: Mekkaoui
authors.forename: David E
authors.initials: DE
authors.lastname: Sosnovik
authors.forename: Sanjay K
authors.initials: SK
authors.lastname: Prasad
authors.forename: David N
authors.initials: DN
authors.lastname: Firmin
authors.forename: Dudley J
authors.initials: DJ
authors.lastname: Pennell
mesh_terms: D000368:Aged; D002312:Cardiomyopathy, Hypertrophic / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D003287:Contrast Media; D056324:Diffusion Tensor Imaging; D005260:Female; D005355:Fibrosis; D006801:Humans; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000473:pathology*; D015588:Observer Variation; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D013318:Stroke Volume; D016277:Ventricular Function, Left
chemical_list: D003287:Contrast Media