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.
Methods and 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). Global MD was significantly higher in the septum than the reference lateral
wall (0.784 ± 0.188 vs 0.750 ± 0.154 x10-3 mm2
/s, p < 0.001). 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