Abstract 4104: Organization of Atrial Signals is Critical Prior to Cardioversion of Atrial Fibrillation with Intravenous Flecainide: Insight from Spectral Analysis of Intracardiac Electrograms

Abstract

Introduction & Hypothesis: Studies in catheter ablation of atrial fibrillation (AF) show that an increase in cycle length (CL) and higher organization index (OI) is associated with termination of AF. We hypothesize that similar changes can be seen in chemical cardioversion with Flecainide Methods: Patients who were still in AF at the end of catheter ablation for AF were given intravenous flecainide. OI and dominant frequency (DF) were obtained by Fast Fourier Transform of coronary sinus electrograms over 10s in AF, before and after flecainide infusion. Mean CL was also calculated. Results: 28 patients were identified (18 paroxysmal AF and 10 persistent AF). 8 cardioverted to sinus rhythm (SR) with flecainide. In all patients, mean CL increased from 211 ± 44 ms to 321 ± 85 ms (p <0.001). Mean DF decreased from 5.2 ± 1.03 Hz to 3.6 ± 1.04 Hz (p <0.001). Mean OI was 0.33 ± 0.13 before and 0.32 ± 0.11 after flecainide (p = 0.90). Comparing patients who cardioverted to SR with those who did not, OI post-flecainide was 0.41 ± 0.12 vs 0.29 ± 0.10 (p=0.013) and relative change in OI was 29 ± 33% vs −3.9 ± 27% (p=0.016) respectively. No significant difference was noted in the change in CL and DF in the 2 groups. Logistic regression showed that a greater relative increase in OI (p=0.04), a higher OI post-flecainide (p=0.03) and SR at start of procedure (p=0.03) are independently associated with cardioversion to SR with flecainide. Conclusion: Increase in OI, independent of changes to the CL and DF, appears critical to AF termination with flecainide. The increase in OI may reflect an increase in size and reduction in the number of re-entrant circuits, which together with slowing of atrial activation, result in return to SR.