Modification of Atrioventricular Node Conduction Increases RR Variability but not RR Irregularity in Atrial Fibrillation Patients

The aim of the present study was to evaluate the effect of rate-control drugs on variability and irregularity of RR series in patients with AF. We analyzed data of 30 patients (age 72 +/- 8 years, 23 men) with permanent AF, from the RATAF (RATe control in Atrial Fibrillation) study. Three 20-min segments were selected at baseline, during beta-blocker (carvedilol) and calcium channel blocker (diltiazem) administration. For every 20-min segment, heart rate (HR) was estimated as well as variability (SDNN, rMSSD, pNN50) and irregularity (regularity index, approximate (ApEn) and sample (SampEn) entropy) of RR intervals. A significant lower HR is obtained with both drugs. Both drugs also increased the variability of ventricular response compared to baseline. On the contrary, only carvedilol increased the irregularity of the RR series. Modification of AV node conduction using beta-blockers or calcium-channel-blockers seems different: both classes of rate-control reduce HR and increase time-domain measures of heart rate variability, but only beta-blockers increase the irregularity measures.