title: Computational fluid dynamics modelling of left valvular heart diseases during atrial fibrillation.
abstract: BACKGROUND
  Although atrial fibrillation (AF), a common arrhythmia, frequently presents in patients with underlying valvular disease, its hemodynamic contributions are not fully understood. The present work aimed to computationally study how physical conditions imposed by pathologic valvular anatomy act on AF hemodynamics.
  
  
  METHODS
  We simulated AF with different severity grades of left-sided valvular diseases and compared the cardiovascular effects that they exert during AF, compared to lone AF. The fluid dynamics model used here has been recently validated for lone AF and relies on a lumped parameterization of the four heart chambers, together with the systemic and pulmonary circulation. The AF modelling involves: (i) irregular, uncorrelated and faster heart rate; (ii) atrial contractility dysfunction. Three different grades of severity (mild, moderate, severe) were analyzed for each of the four valvulopathies (AS, aortic stenosis, MS, mitral stenosis, AR, aortic regurgitation, MR, mitral regurgitation), by varying-through the valve opening angle-the valve area.
  
  
  RESULTS
  Regurgitation was hemodynamically more relevant than stenosis, as the latter led to inefficient cardiac flow, while the former introduced more drastic fluid dynamics variation. Moreover, mitral valvulopathies were more significant than aortic ones. In case of aortic valve diseases, proper mitral functioning damps out changes at atrial and pulmonary levels. In the case of mitral valvulopathy, the mitral valve lost its regulating capability, thus hemodynamic variations almost equally affected regions upstream and downstream of the valve. In particular, the present study revealed that both mitral and aortic regurgitation strongly affect hemodynamics, followed by mitral stenosis, while aortic stenosis has the least impact among the analyzed valvular diseases.
  
  
  CONCLUSIONS
  The proposed approach can provide new mechanistic insights as to which valvular pathologies merit more aggressive treatment of AF. Present findings, if clinically confirmed, hold the potential to impact AF management (e.g., adoption of a rhythm control strategy) in specific valvular diseases.
authors.affiliation: Department of Mechanical and Aerospace Engineering, Politecnico di Torino , Torino , Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Scarsoglio
authors.affiliation: Division of Cardiology, Department of Medical Sciences, "Città della Salute e della Scienza" Hospital, University of Turin , Torino , Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Saglietto
authors.affiliation: Division of Cardiology, Department of Medical Sciences, "Città della Salute e della Scienza" Hospital, University of Turin , Torino , Italy.
authors.forename: Fiorenzo
authors.initials: F
authors.lastname: Gaita
authors.affiliation: Department of Environmental, Land and Infrastructure Engineering, Politecnico di Torino , Torino , Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Ridolfi
authors.affiliation: Division of Cardiology, Department of Medical Sciences, "Città della Salute e della Scienza" Hospital, University of Turin , Torino , Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Anselmino
keywords: Atrial fibrillation; Cardiovascular system; Computational hemodynamics; Fluid dynamics; Heart valve diseases; Lumped parameter modelling