title: Cardiac magnetic resonance T1 mapping of left atrial myocardium.
abstract: BACKGROUND
  Cardiac magnetic resonance (CMR) T1 mapping is an emerging tool for objective quantification of myocardial fibrosis.
  
  
  OBJECTIVE
  To (a) establish the feasibility of left atrial (LA) T1 measurements, (b) determine the range of LA T1 values in patients with atrial fibrillation (AF) vs healthy volunteers, and (c) validate T1 mapping vs LA intracardiac electrogram voltage amplitude measures.
  
  
  METHODS
  CMR imaging at 1.5 T was performed in 51 consecutive patients before AF ablation and in 16 healthy volunteers. T1 measurements were obtained from the posterior LA myocardium by using the modified Look-Locker inversion-recovery sequence. Given the established association of reduced electrogram amplitude with fibrosis, intracardiac point-by-point bipolar LA voltage measures were recorded for the validation of T1 measurements.
  
  
  RESULTS
  The median LA T1 relaxation time was shorter in patients with AF (387 [interquartile range 364-428] ms) compared to healthy volunteers (459 [interquartile range 418-532] ms; P < .001) and was shorter in patients with AF with prior ablation compared to patients without prior ablation (P = .035). In a generalized estimating equations model, adjusting for data clusters per participant, age, rhythm during CMR, prior ablation, AF type, hypertension, and diabetes, each 100-ms increase in T1 relaxation time was associated with 0.1 mV increase in intracardiac bipolar LA voltage (P = .025).
  
  
  CONCLUSIONS
  Measurement of the LA myocardium T1 relaxation time is feasible and strongly associated with invasive voltage measures. This methodology may improve the quantification of fibrotic changes in thin-walled myocardial tissues.
authors: Division of Cardiology, Johns Hopkins University, Baltimore, Maryland MD 21287, USA. rbeiner1@jhmi.edu
authors: Roy
authors: R
authors: Beinart
authors: Irfan M
authors: IM
authors: Khurram
authors: Songtao
authors: S
authors: Liu
authors: Hirad
authors: H
authors: Yarmohammadi
authors: Henry R
authors: HR
authors: Halperin
authors: David A
authors: DA
authors: Bluemke
authors: Neville
authors: N
authors: Gai
authors: Rob J
authors: RJ
authors: van der Geest
authors: Joao A C
authors: JA
authors: Lima
authors: Hugh
authors: H
authors: Calkins
authors: Stefan L
authors: SL
authors: Zimmerman
authors: Saman
authors: S
authors: Nazarian
mesh_terms: D001281:Atrial Fibrillation / Q000175:diagnosis / Q000503:physiopathology* / Q000601:surgery; D016279:Atrial Function, Left / Q000502:physiology*; D009202:Cardiomyopathies / Q000175:diagnosis; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D005355:Fibrosis; D005682:Gadolinium; D006325:Heart Atria / Q000473:pathology*; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D007089:Image Enhancement; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000473:pathology*
chemical_list: D005682:Gadolinium
keywords: AF; Atrial fibrillation; CI; CMR; Cardiac magnetic resonance; GEE; IQR; LA; LGE-CMR; LV; Late gadolinium enhancement; Left atrial fibrosis; PVAI; ROI; T1 mapping; atrial fibrillation; cardiac magnetic resonance; confidence interval; generalized estimating equation; interquartile range; late gadolinium enhancement on cardiac magnetic resonance; left atrial; left ventricular; pulmonary vein antral isolation; region of interest
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