title: Insight into hypertrophied hearts: a cardiovascular magnetic resonance study of papillary muscle mass and T1 mapping.
abstract: OBJECTIVE
  Left ventricular papillary muscles (LVPM) can appear disproportionately hypertrophied, particularly in Fabry disease (FD) where storage appears detectable by cardiovascular magnetic resonance (CMR) T1 mapping. The aim of the study was to measure LVPM mass in heart diseases with left ventricular hypertrophy (LVH) and to gain insight into the mechanisms of LVPM hypertrophy in FD.
  
  
  RESULTS
  Four hundred and seventy-eight cases were retrospectively recruited: 125 FD, 85 hypertrophic cardiomyopathy (HCM), 67 amyloid, 82 aortic stenosis (AS), 40 hypertension, 79 controls. LVPM contribution to LVM was manually contoured on CMR short axis cines. T1 values (septal, LVPM) were measured using ShMOLLI sequences in FD and controls. LVPM contribution to LVM was highest in LVH+ve FD and significantly increased compared to all other LVH+ve groups (FD 13 ± 3%, HCM 10 ± 3%, amyloid 8 ± 2%, AS 7 ± 3%, hypertension 7 ± 2%, controls 7 ± 1%; P < 0.001). LVH+ve HCM also had significantly increased LVPM. In LVH-ve cohorts, only FD had significantly increased LVPM (11 ± 3%; P < 0.001). In FD there was concordant septal and LVPM T1. LVH+ve FD: when septal T1 was low, LVPM T1 was low in 90%. LVH-ve FD: when septal T1 was normal, LVPM T1 was normal in 70% (indicating no detectable storage); when septal T1 was low, 75% had low LVPM T1 (indicating storage). LVPM hypertrophy was similar between the low and normal septal T1 groups (11 ± 3% vs. 10 ± 3%, P = 0.08).
  
  
  CONCLUSIONS
  Disproportionate hypertrophy of LVPMs in LVH+ve hearts occurred in FD and HCM. This phenomenon also occurred in LVH-ve FD. Low T1 was not always present in FD LVPM hypertrophy, implying additional mechanisms activating hypertrophy signalling pathways.
authors: Barts Heart Centre, London, UK.|Sydney Medical School, University of Sydney, Sydney, Australia.
authors: Rebecca
authors: R
authors: Kozor
authors: Barts Heart Centre, London, UK.|Institute of Cardiovascular Science, University College London, London, UK.
authors: Sabrina
authors: S
authors: Nordin
authors: Barts Heart Centre, London, UK.|Institute of Cardiovascular Science, University College London, London, UK.
authors: Thomas A
authors: TA
authors: Treibel
authors: Barts Heart Centre, London, UK.
authors: Stefania
authors: S
authors: Rosmini
authors: Barts Heart Centre, London, UK.
authors: Silvia
authors: S
authors: Castelletti
authors: National Amyloidosis Centre, Royal Free Hospital, University College London, London, UK.
authors: Marianna
authors: M
authors: Fontana
authors: Barts Heart Centre, London, UK.
authors: Gabriella
authors: G
authors: Captur
authors: University Hospitals Birmingham, Birmingham, UK.
authors: Shanat
authors: S
authors: Baig
authors: University Hospitals Birmingham, Birmingham, UK.
authors: Richard P
authors: RP
authors: Steeds
authors: Lysosomal Storage Disorders Unit, Royal Free Hospital, University College London, London, UK.
authors: Derralynn
authors: D
authors: Hughes
authors: Barts Heart Centre, London, UK.|National Amyloidosis Centre, Royal Free Hospital, University College London, London, UK.
authors: Charlotte
authors: C
authors: Manisty
authors: Sydney Medical School, University of Sydney, Sydney, Australia.
authors: Stuart M
authors: SM
authors: Grieve
authors: Sydney Medical School, University of Sydney, Sydney, Australia.
authors: Gemma A
authors: GA
authors: Figtree
authors: Barts Heart Centre, London, UK.|Institute of Cardiovascular Science, University College London, London, UK.
authors: James C
authors: JC
authors: Moon
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D016022:Case-Control Studies; D000795:Fabry Disease / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D006801:Humans; D017379:Hypertrophy, Left Ventricular / Q000000981:diagnostic imaging* / Q000473:pathology*; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010210:Papillary Muscles / Q000473:pathology; D011379:Prognosis; D011856:Radiographic Image Enhancement; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D006113:United Kingdom
keywords: cardiovascular magnetic resonance; fabry disease; hypertrophy; papillary muscle