title: Left ventricular beat-to-beat performance in atrial fibrillation: contribution of Frank-Starling mechanism after short rather than long RR intervals.
abstract: OBJECTIVE
  This study sought to evaluate control mechanism of the varying left ventricular performance in atrial fibrillation.
  
  
  BACKGROUND
  Atrial fibrillation is characterized by a randomly irregular ventricular response, resulting in continuous variation in left ventricular beat-to-beat mechanical behavior and hemodynamic variables.
  
  
  METHODS
  Fourteen patients with chronic nonvalvular atrial fibrillation were studied, using a nonimaging computerized nuclear probe linked to a personal computer. Left ventricular ejection fraction, end-diastolic and end-systolic volume counts, stroke volume counts and filling time were calculated on a beat-to-beat basis during 500 consecutive RR intervals. Multiple regression analysis was used to assess how ejection fraction was predicted by these variables.
  
  
  RESULTS
  The preceding RR interval and end-diastolic volume showed a positive relation, and prepreceding interval and end-systolic volume an inverse relation, with ejection fraction (all p < 0.001). Sensitivity analysis suggested that the preceding interval and the end-diastolic volume were equally important in predicting ejection fraction. There was a relatively strong interaction between the preceding interval and end-diastolic volume, indicating that the influence of the end-diastolic volume on ejection fraction was diminished after long intervals. A second interaction showed that the effect of end-diastolic volume on ejection fraction was attenuated after short prepreceding cycles.
  
  
  CONCLUSIONS
  Cycle length-dependent contractile mechanisms, including postextrasystolic potentiation and mechanical restitution, determine the varying left ventricular systolic performance during atrial fibrillation over the entire range of intervals. Beat-to-beat changes in preload, consistent with the Frank-Starling mechanism, also play a role, but their influence is diminished after long preceding and short prepreceding intervals.
authors.affiliation: Department of Cardiology, University Hospital Groningen, The Netherlands.
authors.forename: A T
authors.initials: AT
authors.lastname: Gosselink
authors.forename: P K
authors.initials: PK
authors.lastname: Blanksma
authors.forename: H J
authors.initials: HJ
authors.lastname: Crijns
authors.forename: I C
authors.initials: IC
authors.lastname: Van Gelder
authors.forename: P J
authors.initials: PJ
authors.lastname: de Kam
authors.forename: H L
authors.initials: HL
authors.lastname: Hillege
authors.forename: M G
authors.initials: MG
authors.lastname: Niemeijer
authors.forename: K I
authors.initials: KI
authors.lastname: Lie
authors.forename: F L
authors.initials: FL
authors.lastname: Meijler
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D013318:Stroke Volume / Q000502:physiology*; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology*