Quantification of phase recurrences in atrioventricular (AV) conduction during atrial arrhythmias

In this study we propose a new method to characterize atrioventricular (AV) coupling during atrial arrhythmias, based on the quantification of the recurrences of the AV phase series, which represents the timing of atrial beats with respect to subsequent ventricular beats. Recurrences are quantified in terms of autocorrelation function maximum (R), Shannon Entropy (SE) and synchrogram features (locking ratio LR, presence p and length k of phase-locked epochs). AV phase series obtained during type I and II atrial flutter (AFL1 and AFL2) and atrial fibrillation (AF) showed the existence of significant phase-locked segments, whose presence, length and locking ratios decreased at increasing atrial frequency and complexity (AFL1: R=0.99±0.01, SE=1.13±0.52, p=99.5±0.9%, k=96.3±30.4, LR=0.37±0.15; AFL2: R=0.75±0.01, SE=2.99±0.01, p=57.3±8.8%, k=2.42±0.54, LR=0.23±0.02; AF: R=0.77±0.06, SE=2.90±0.25, p=70.8±18.9%, k=2.24±0.29, LR=0.34±0.06). The quantification of AV phase recurrences could have basic as well as clinical applications for understanding AV node dynamics during atrial arrhythmias and characterizing AV pharmacological control.