title: Atrial fibrillation in patients admitted to coronary care units in western Sweden - focus on obesity and lipotoxicity.
abstract: BACKGROUND
  Atrial fibrillation (AF) is the most common form of arrhythmia in humans and is associated with substantial morbidity and mortality. Obesity and diabetes have been linked to myocardial lipotoxicity - a condition where the heart accumulates and produces toxic lipid species. We hypothesized that obesity and diabetes were involved in the pathophysiology of AF by means of promoting a lipotoxic phenotype in atrial muscle, and that AF predicts mortality in cardiac care patients.
  
  
  METHODS
  Our study consists of two parts. The first part is a registry study based on prospective data obtained through the Register of Information and Knowledge about Swedish Heart Intensive Care Admissions (RIKS-HIA) from hospitals in western Sweden. All consecutive patients between 2006 and 2011 admitted to coronary care unit (CCU) with sinus rhythm (SR) or AF were included in the analysis. Multivariate logistic regression and Cox proportional-hazards regression were used to test whether diabetes and obesity were independent predictors of AF at admission to CCU and whether AF was associated with increased one-year mortality. In the second part we obtained atrial biopsies from 54 patients undergoing cardiac surgery and performed lipidomic analysis for a detailed qualitative and quantitative analysis of lipid species including triglycerides (TAG), ceramides (CER), phosphatidylcholine (PC), lysophosphatidylcholine (LPC), phosphatidylethanolamine (PE), sphyngomyelins (SM), free cholesterol (FC), cholesterol esters (CEs) and diacylglycerols (DAGs).
  
  
  RESULTS
  Between 2006 and 2011, 35232 patients were admitted to CCUs in western Sweden, mostly due to ischemic heart disease, heart failure, arrhythmia, syncope and chest pain. The mean age was 66years and 58.7% were male. There was a high prevalence of obesity (20.3%) and diabetes (16.8%). Obesity (OR 1.35, 95% CI 1.17-1.56, P<0.001) and severe obesity (1.6, 95% CI 1.29-1.99, P<0.001) were independent predictors of AF but diabetes was not (OR=0.92, 95% CI=0.82-1.04). AF increased one-year mortality (HR 1.32, 95% CI 1.16-1.50, P<0.001). Lipidomic analysis revealed that atrial TAG content was substantially lower in the AF patients (P<0.05). No quantitative difference was found in the content of CER, PC, LPC, PE, SM, FC, CE and DAG, between the patients who had AF or sinus rhythm at admission to the CCU. AF patients had greater proportion of polyunsaturated DAG (P<0.05) while no difference was found in saturated DAG.
  
  
  CONCLUSIONS
  Obesity but not diabetes is an independent predictor of AF and AF is associated with increased one-year mortality in this CCU population. AF is associated with quantitative and qualitative alterations in atrial lipid content but not with lipotoxicity.
authors: Department of Molecular and Clinical Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors: Sigfus
authors: S
authors: Gizurarson
authors: Department of Molecular and Clinical Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors: Marcus
authors: M
authors: Ståhlman
authors: Department of Molecular and Clinical Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors: Anders
authors: A
authors: Jeppsson
authors: Department of Molecular and Clinical Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors: Yangzhen
authors: Y
authors: Shao
authors: Department of Molecular and Clinical Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors: Björn
authors: B
authors: Redfors
authors: Department of Molecular and Clinical Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors: Lennart
authors: L
authors: Bergfeldt
authors: Department of Molecular and Clinical Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors: Jan
authors: J
authors: Borén
authors: Department of Molecular and Clinical Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. Electronic address: elmir@wlab.gu.se.
authors: Elmir
authors: E
authors: Omerovic
mesh_terms: D017677:Age Distribution; D000368:Aged; D001281:Atrial Fibrillation / Q000453:epidemiology* / Q000378:metabolism; D015984:Causality; D015897:Comorbidity; D003325:Coronary Care Units / Q000706:statistics & numerical data; D058065:Diabetic Cardiomyopathies / Q000453:epidemiology* / Q000378:metabolism; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D050356:Lipid Metabolism; D052439:Lipid Metabolism Disorders / Q000453:epidemiology* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000453:epidemiology* / Q000378:metabolism; D012042:Registries; D018570:Risk Assessment; D017678:Sex Distribution; D013548:Sweden / Q000453:epidemiology
keywords: Atrial biopsy; Atrial fibrillation; Diabetes; Lipotoxicity; Obesity