title: Left atrial fibrosis quantification by late gadolinium-enhanced magnetic resonance: a new method to standardize the thresholds for reproducibility.
abstract: OBJECTIVE
  Identification of left atrial (LA) fibrosis through late gadolinium-enhanced cardiac magnetic resonance (LGE-CMR) remains controversial due to the heterogeneity and lack of reproducibility of proposed methods. Our aim is to describe a normalized, reproducible, standardized method to evaluate LA fibrosis through LGE-CMR.
  
  
  RESULTS
  Electrocardiogram- and respiratory-gated 3-Tesla LGE-CMR was performed in 10 healthy young volunteers and 30 patients with atrial fibrillation (AF): 10 with paroxysmal AF, 10 with persistent AF, and 10 with a previous AF ablation procedure. Local image intensity ratio (IIR) of the LA was calculated as the absolute pixel intensity to mean blood pool intensity ratio. The healthy atrial tissue threshold was defined in young healthy volunteers (upper limit of normality set at IIR tissue mean plus 2 SDs). Dense atrial scarring was characterized in patients with previous radiofrequency-induced scarring (post-AF ablation patients). Validation groups consisted of patients with paroxysmal and persistent AFs. The upper limit of normal IIR was 1.20; IIR values higher than 1.32 (60% of mean maximum pixel intensity in post-ablation patients) were considered dense scar. Image intensity ratio values between 1.2 and 1.32 identified interstitial fibrosis. Patients with paroxysmal and persistent AFs had less atrial fibrotic tissue compared with post-ablation patients. Endocardial bipolar voltage was correlated to IIR values.
  
  
  CONCLUSIONS
  An IIR of 1.2 identifies the upper limit of normality in healthy young individuals. An IIR of >1.32 defines dense atrial fibrosis in post-ablation patients. Our results provide a consistent, comparable, and normalized tool to assess atrial arrhythmogenic substrate.
authors.affiliation: Department of Cardiology, Unitat de Fibril·lació Auricular (UFA), Hospital Clinic, Universitat de Barcelona, Villarroel 170, 08036 Barcelona, Catalonia, Spain.|Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Catalonia, Spain.
authors.forename: Eva M
authors.initials: EM
authors.lastname: Benito
authors.affiliation: Department of Cardiology, Unitat de Fibril·lació Auricular (UFA), Hospital Clinic, Universitat de Barcelona, Villarroel 170, 08036 Barcelona, Catalonia, Spain.|Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Catalonia, Spain.
authors.forename: Alicia
authors.initials: A
authors.lastname: Carlosena-Remirez
authors.affiliation: Department of Cardiology, Unitat de Fibril·lació Auricular (UFA), Hospital Clinic, Universitat de Barcelona, Villarroel 170, 08036 Barcelona, Catalonia, Spain.|Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Catalonia, Spain.
authors.forename: Eduard
authors.initials: E
authors.lastname: Guasch
authors.affiliation: Department of Cardiology, Unitat de Fibril·lació Auricular (UFA), Hospital Clinic, Universitat de Barcelona, Villarroel 170, 08036 Barcelona, Catalonia, Spain.|Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Catalonia, Spain.
authors.forename: Susana
authors.initials: S
authors.lastname: Prat-González
authors.affiliation: Department of Cardiology, Unitat de Fibril·lació Auricular (UFA), Hospital Clinic, Universitat de Barcelona, Villarroel 170, 08036 Barcelona, Catalonia, Spain.|Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Catalonia, Spain.
authors.forename: Rosario J
authors.initials: RJ
authors.lastname: Perea
authors.affiliation: Department of Cardiology, Unitat de Fibril·lació Auricular (UFA), Hospital Clinic, Universitat de Barcelona, Villarroel 170, 08036 Barcelona, Catalonia, Spain.|Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Catalonia, Spain.
authors.forename: Rosa
authors.initials: R
authors.lastname: Figueras
authors.affiliation: Department of Cardiology, Unitat de Fibril·lació Auricular (UFA), Hospital Clinic, Universitat de Barcelona, Villarroel 170, 08036 Barcelona, Catalonia, Spain.|Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Catalonia, Spain.
authors.forename: Roger
authors.initials: R
authors.lastname: Borràs
authors.affiliation: Department of Cardiology, Unitat de Fibril·lació Auricular (UFA), Hospital Clinic, Universitat de Barcelona, Villarroel 170, 08036 Barcelona, Catalonia, Spain.|Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Catalonia, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Andreu
authors.affiliation: Department of Cardiology, Unitat de Fibril·lació Auricular (UFA), Hospital Clinic, Universitat de Barcelona, Villarroel 170, 08036 Barcelona, Catalonia, Spain.|Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Catalonia, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: Arbelo
authors.affiliation: Department of Cardiology, Unitat de Fibril·lació Auricular (UFA), Hospital Clinic, Universitat de Barcelona, Villarroel 170, 08036 Barcelona, Catalonia, Spain.|Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Catalonia, Spain.
authors.forename: J Maria
authors.initials: JM
authors.lastname: Tolosana
authors.affiliation: Department of Cardiology, Unitat de Fibril·lació Auricular (UFA), Hospital Clinic, Universitat de Barcelona, Villarroel 170, 08036 Barcelona, Catalonia, Spain.|Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Catalonia, Spain.
authors.forename: Felipe
authors.initials: F
authors.lastname: Bisbal
authors.affiliation: Department of Cardiology, Unitat de Fibril·lació Auricular (UFA), Hospital Clinic, Universitat de Barcelona, Villarroel 170, 08036 Barcelona, Catalonia, Spain.|Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Catalonia, Spain.
authors.forename: Josep
authors.initials: J
authors.lastname: Brugada
authors.affiliation: Department of Cardiology, Unitat de Fibril·lació Auricular (UFA), Hospital Clinic, Universitat de Barcelona, Villarroel 170, 08036 Barcelona, Catalonia, Spain.|Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Catalonia, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Berruezo
authors.affiliation: Department of Cardiology, Unitat de Fibril·lació Auricular (UFA), Hospital Clinic, Universitat de Barcelona, Villarroel 170, 08036 Barcelona, Catalonia, Spain.|Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Catalonia, Spain.
authors.forename: Lluis
authors.initials: L
authors.lastname: Mont
mesh_terms: D000200:Action Potentials; D000293:Adolescent; D000328:Adult; D000368:Aged; D001281:Atrial Fibrillation / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D064752:Atrial Remodeling; D055424:Cardiac-Gated Imaging Techniques; D016022:Case-Control Studies; D017115:Catheter Ablation; D003287:Contrast Media / Q000008:administration & dosage*; D004562:Electrocardiography; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D005355:Fibrosis; D006325:Heart Atria / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000592:standards*; D008297:Male; D008875:Middle Aged; D009942:Organometallic Compounds / Q000008:administration & dosage*; D011237:Predictive Value of Tests; D012016:Reference Values; D015203:Reproducibility of Results; D055815:Young Adult
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; C090600:gadobutrol
keywords: Atrial fibrillation; Atrial fibrosis; Catheter ablation; Late gadolinium enhancement; Magnetic resonance