title: Characterization of rate and regularity of ventricular response during atrial tachyarrhythmias. Insight on atrial and nodal determinants.
abstract: OBJECTIVE
  Ventricular rate and regularity affect hemodynamic stability and are targets of rate control therapy in patients with atrial flutter (AFL) and atrial fibrillation (AF). Nevertheless, the characteristics and determinants of ventricular response during these atrial arrhythmias are poorly understood. This work aims to investigate the effects of changes in atrial activity and atrioventricular (AV) conduction patterns on ventricular response in patients with atrial tachyarrhythmias by a combined quantitative analysis of atrial and ventricular time series.
  
  
  METHODS
  Time series were determined in patients during 24 episodes of AFL and 13 episodes of AF. Ventricular response was characterized in terms of mean ventricular interval, time-domain variability parameters, and entropy-based irregularity measures (quadratic entropy rate, QSE, and coefficient of sample entropy, COSEn). Atrial activity was characterized in terms of mean atrial rate and variability. AV conduction was analyzed by AV synchrogram method, quantifying the stability of AV coupling and the average AV conduction ratio. The dependence of ventricular features on atrial/AV determinants was investigated by correlation analysis.
  
  
  RESULTS
  The analysis showed ventricular response to display a wide spectrum of variability and irregularity features at changing atrial and AV properties. The ventricular interval was significantly correlated with the AV conduction ratio (Spearman correlation coefficient ρ  =  -0.76, p  <  0.005), while it did not correlate with atrial rate. The variability and irregularity of ventricular response were influenced by both atrial and AV parameters. QSE and COSEn significantly increased at shorter atrial cycle lengths (ρ  =  -0.67 and  -0.71, p  <  0.005), at higher atrial variability (ρ  =  0.80 and 0.77, p  <  0.005), at reduced AV coupling (ρ  =  -0.91, p  <  0.005) and at smaller AV conduction ratios (ρ  =  -0.65 and  -0.52, p  <  0.005).
  
  
  CONCLUSIONS
  The identification of the determinants of ventricular rate and regularity may have significant implications in the development of efficacious rate control strategies in patients with atrial tachyarrhythmias.
authors.affiliation: Department of Physics, University of Trento, Trento, Italy.
authors.forename: Michela
authors.initials: M
authors.lastname: Masè
authors.forename: Marcello
authors.initials: M
authors.lastname: Disertori
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Marini
authors.forename: Flavia
authors.initials: F
authors.lastname: Ravelli
mesh_terms: D000368:Aged; D004562:Electrocardiography; D005260:Female; D006325:Heart Atria / Q000503:physiopathology*; D006329:Heart Conduction System / Q000503:physiopathology; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D008297:Male; D013610:Tachycardia / Q000503:physiopathology*; D013997:Time Factors