title: 4D flow MRI and T1 -Mapping: Assessment of altered cardiac hemodynamics and extracellular volume fraction in hypertrophic cardiomyopathy.
abstract: OBJECTIVE
  Hypertrophic cardiomyopathy (HCM) is associated with altered hemodynamics in the left ventricular outflow tract (LVOT) and myocardial tissue abnormalities such as fibrosis. The aim of this study was to quantify changes in LVOT 3D hemodynamics and myocardial extracellular volume fraction (ECV, measure of fibrosis) and to investigate relationships between elevated flow metrics and left ventricular (LV) tissue abnormalities.
  
  
  METHODS
  Cardiac magnetic resonance imaging (MRI) including 4D flow (field strength = 1.5T, resolution = 2.1-4.0 × 2.1-4.0 × 2.5-3.2 mm(3) ; venc = 150-250 cm/s; TE/TR/FA = 2.2-2.5msec/4.6-4.9msec/15°) for the in vivo assessment of 3D blood flow velocities with full coverage of the LVOT was applied in 35 patients with HCM (54 ± 15 years) and 10 age-matched healthy controls (45 ± 14 years). In addition, pre- and postcontrast myocardial T1 -mapping (resolution = 2.3 × 1.8 mm, slice thickness = 8 mm, TE/TR-FA = 1.0-1.1msec/2.0-2.2msec/35°) of the LV (basal, mid-ventricular, apical short axis) was performed in a subgroup of 23 HCM patients. Analysis included the segmentation of the LVOT and quantification of peak systolic LVOT pressure gradients and rate of viscous energy loss EL ' as well as left ventricular ECV.
  
  
  RESULTS
  HCM patients demonstrated significantly elevated peak systolic LVOT pressure gradients (21 ± 16 mmHg vs. 9 ± 2 mmHg) and energy loss EL ' (3.8 ± 2.5 mW vs. 1.5 ± 0.7 mW, P < 0.005) compared to controls. There was a significant relationship between increased LV fibrosis (ECV) with both elevated pressure gradients (R(2) = 0.44, P < 0.001) and energy loss EL ' (R(2) = 0.46, P < 0.001).
  
  
  CONCLUSIONS
  The integration of 4D-flow and T1 -mapping-MRI allowed for the evaluation of tissue and flow abnormalities in HCM patients. Our findings suggest a mechanistic link between abnormal LVOT flow, increased LV loading, and adverse myocardial remodeling in HCM.
authors.affiliation: Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
authors.forename: Pim
authors.initials: P
authors.lastname: van Ooij
authors.affiliation: Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
authors.forename: Bradley D
authors.initials: BD
authors.lastname: Allen
authors.affiliation: Department of Medicine-Cardiology, Northwestern University, Chicago, Illinois, USA.
authors.forename: Carla
authors.initials: C
authors.lastname: Contaldi
authors.affiliation: Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
authors.forename: Julio
authors.initials: J
authors.lastname: Garcia
authors.affiliation: Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Collins
authors.affiliation: Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
authors.forename: James
authors.initials: J
authors.lastname: Carr
authors.affiliation: Department of Medicine-Cardiology, Northwestern University, Chicago, Illinois, USA.
authors.forename: Lubna
authors.initials: L
authors.lastname: Choudhury
authors.affiliation: Department of Medicine-Cardiology, Northwestern University, Chicago, Illinois, USA.
authors.forename: Robert O
authors.initials: RO
authors.lastname: Bonow
authors.affiliation: Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
authors.forename: Alex J
authors.initials: AJ
authors.lastname: Barker
authors.affiliation: Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.|Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Chicago, Illinois, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Markl
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001810:Blood Volume; D001811:Blood Volume Determination / Q000379:methods; D055424:Cardiac-Gated Imaging Techniques / Q000379:methods*; D002312:Cardiomyopathy, Hypertrophic / Q000175:diagnosis* / Q000503:physiopathology*; D045604:Extracellular Fluid / Q000378:metabolism; D005260:Female; D006352:Heart Ventricles / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013318:Stroke Volume; D055815:Young Adult
keywords: 4D flow MRI; T1-mapping; extracellular volume fraction; fibrosis; hypertrophic cardiomyopathy; pressure gradient