High-density mapping of atrial fibrillation in humans: relationship between high-frequency activation and electrogram fractionation

Characteristics and distribution of complex fractionated atrial electrograms in patients with paroxysmal and persistent atrial fibrillation

INTRODUCTION

Substrate-based radiofrequency ablation for treatment of atrial fibrillation (AF) is still under development. The purpose of this study was to investigate the different characteristics and distribution of complex fractionated atrial electrograms (CFAE) in both atria in patients with paroxysmal and persistent AF.

METHODS AND RESULTS

The NavX system was used to map the left and right atria and the coronary sinus in 20 AF patients (ten persistent). An automated algorithm calculates the average time interval between consecutive deflections (complex fractionated electrogram (CFE) mean). All recordings were visually inspected off-line and interpreted either as continuous, fragmented, mixed CFAE, or non-CFAE, and their locations were determined. Electrograms with intermittent CFAE characteristics were also regarded as non-CFAEs. There were more CFAEs in persistent AF than in paroxysmal AF (52% vs. 44% of total registrations, p < 0.05), and CFAEs were more widespread in both atria in persistent AF patients. There were also more continuous CFAEs (70% vs. 59% of total CFAEs, p < 0.05), and less mixed and intermittent CFAEs (22% vs. 30% and 16% vs. 21% of total CFAEs, respectively, p < 0.05) in persistent AF. Fragmented CFAEs had more high-voltage signals than other groups. Employing the automated algorithm for CFAE mapping, a CFE mean cut-off value of < or =80 ms provides a sensitivity and specificity of 87.4% and 81.2%, respectively.

CONCLUSIONS

CFAEs distribute in preferential areas and arrange in different patterns in both atria. Patients with persistent AF have more continuous CFAEs and higher temporal signal stability than patients with paroxysmal AF.

Impact of pharmacological autonomic blockade on complex fractionated atrial electrograms

INTRODUCTION

The influence of the autonomic nervous system on the pathogenesis of complex fractionated atrial electrograms (CFAE) during atrial fibrillation (AF) is incompletely understood. This study evaluated the impact of pharmacological autonomic blockade on CFAE characteristics.

METHODS AND RESULTS

Autonomic blockade was achieved with propanolol and atropine in 29 patients during AF. Three-dimensional maps of the fractionation degree were made before and after autonomic blockade using the Ensite Navx system. In 2 patients, AF terminated following autonomic blockade. In the remaining 27 patients, 20,113 electrogram samples of 5 seconds duration were collected randomly throughout the left atrium (10,054 at baseline and 10,059 after autonomic blockade). The impact of autonomic blockade on fractionation was assessed by blinded investigators and related to the type of AF and AF cycle length. Globally, CFAE as a proportion of all atrial electrogram samples were reduced after autonomic blockade: 61.6 +/- 20.3% versus 57.9 +/- 23.7%, P = 0.027. This was true/significant for paroxysmal AF (47 +/- 23% vs 40 +/- 22%, P = 0.003), but not for persistent AF (65 +/- 22% vs 62 +/- 25%, respectively, P = 0.166). Left atrial AF cycle length prolonged with autonomic blockade from 170 +/- 33 ms to 180 +/- 40 ms (P = 0.001). Fractionation decreases only in the 14 of 27 patients with a significant (>6 ms) prolongation of the AF cycle length (64 +/- 20% vs 59 +/- 24%, P = 0.027), whereas fractionation did not reduce when autonomic blockade did not affect the AF cycle length (58 +/- 21% vs 56 +/- 25%, P = 0.419).

CONCLUSIONS

Pharmacological autonomic blockade reduces CFAE in paroxysmal AF, but not persistent AF. This effect appears to be mediated by prolongation of the AF cycle length.

Paroxysmal atrial fibrillation maintained by nonpulmonary vein sources can be predicted by dominant frequency analysis of atriopulmonary electrograms

INTRODUCTION

Increasing evidence suggests that high-frequency excitation in the pulmonary vein (PV) plays a dominant role in the maintenance of paroxysmal atrial fibrillation (AF). However, in a certain population of patients, AF remains inducible after PV isolation (PVI). We sought to clarify whether dominant frequency (DF) analysis of atriopulmonary electrograms can predict paroxysmal AF maintained by non-PV sources.

METHODS AND RESULTS

Sixty-one patients with paroxysmal AF (aged 59 +/- 12 years) were studied. Before PVI, bipolar electrograms during AF were recorded simultaneously from three PV ostia, the coronary sinus (CS), and the septum and free wall of the right atrium (RA). DF was obtained by fast Fourier transform (FFT) analysis. AF was rendered noninducible after PVI in 39 of the 61 patients (noninducible group), but was still inducible in the remaining 22 (inducible group). Among the six recording sites, the highest DF was documented in the PV in all of the patients in the noninducible group; the maximum DF among the three PVs (PV-DF(max)) was higher than that among the CS and two RA sites (atrial DF(max); 7.2 +/- 1.0 Hz vs 5.8 +/- 0.7 Hz, P < 0.0001). In contrast, the highest DF was documented in the CS or RA in 45.5% of the patients in the inducible group; PV-DF(max) was comparable with atrial DF(max) (6.6 +/- 0.8 Hz vs 6.6 +/- 0.6 Hz). AF inducibility after PVI was predicted by a PV-to-atrial DF(max) gradient of <0.5 Hz, with a sensitivity of 90.9% and a specificity of 89.7%.

CONCLUSION

Paroxysmal AF maintained by non-PV sources can be predicted by the PV-to-atrial DF gradient.

Differences in atrial fibrillation properties under vagal nerve stimulation versus atrial tachycardia remodeling

BACKGROUND

There are many similarities between atrial effects of atrial tachycardia remodeling (ATR) and vagal nerve stimulation (VS): both promote atrial fibrillation (AF), reduce atrial effective refractory period (AERP) and AERP rate accommodation, enhance AERP heterogeneity, and increase inward-rectifier K+ current.

OBJECTIVE

This study sought to compare the consequences of ATR and VS at similar levels of AERP abbreviation in dogs.

METHODS

ATR dogs (n = 6) were subjected to 7-day atrial tachypacing at 400 beats/min, with radiofrequency-induced atrioventricular block and ventricular demand pacing (80 beats/min) to control ventricular response. VS was applied in 6 matched dogs with stimulation parameters selected to produce similar mean AERP values to ATR dogs.

RESULTS

ATR and VS produced similarly short AERPs (79 +/- 12 and 80 +/- 12 ms, respectively), AERP rate-adaptation loss, and AERP heterogeneity increases. Although both ATR and VS increased AF duration, VS was significantly more effective in AF promotion, with mean AF duration of 992 +/- 134 seconds, versus 440 +/- 240 seconds (P <.05) under ATR. The greater AF-promoting effect of VS was associated with greater mean dominant frequency values during AF (11.7 +/- 1.8 versus 10.0 +/- 1.3 Hz ATR, P <.05). VS greatly enhanced the spatial dominant frequency variability, increasing the coefficient of variation to 15.2 +/- 1.9 Hz, versus 8.9 +/- 1.5 Hz for ATR (P <.05), primarily by increasing the per-dog maximum dominant frequency (15.4 +/- 0.6 Hz versus 12.5 +/- 0.6 for ATR, P <.01).

CONCLUSION

For matched AERP values, VS promotes AF more strongly than ATR. Despite similar AERP changes, VS produces considerably greater increases in dominant frequencies, particularly maximum values, consistent with previous suggestions that inward-rectifier K+ current enhancement is particularly effective at accelerating and stabilizing spiral wave rotors that maintain AF.