Original-clinicalVagal responses induced by endocardial left atrial autonomic ganglion stimulation before and after pulmonary vein antrum isolation for atrial fibrillation
Introduction
Ever since Armour et al1 reported on the anatomy of the intrinsic cardiac nervous system in humans, it has been suggested that autonomic inputs from ganglionated plexi that surround the heart may contribute to both the initiation and maintenance of atrial fibrillation (AF). High-frequency stimulation of epicardial autonomic plexi can induce triggered activity from the pulmonary veins (PVs)2 and also affect atrial refractory periods to provide a substrate for the conversion of PV firing into sustained AF.3, 4 More specifically, increased vagal tone has been shown to be a trigger for AF in a subset of patients.5 Enhanced vagal tone can increase the inducibility of AF,6 and elimination of vagal inputs may prevent AF recurrence in both animal and patient models of vagal AF.7, 8
Radiofrequency (RF) ablation has emerged as an effective therapy for patients with symptomatic AF. The traditional approach of ablation has been to eliminate all of the triggers for AF by isolating the PVs.9 Recent data has suggested that identification and ablation of autonomic ganglia (AG) during PV isolation may improve long-term success.10 However, it is unknown whether these regions are already modified during standard PV antrum isolation (PVAI). AG responses are also unknown in patients who have AF recurrence postablation. Thus, the purpose of this study was (1) to assess the effects of standard PVAI guided by intracardiac echocardiography (ICE) on vagal responses induced by AG stimulation and (2) to assess vagal responses induced by AG stimulation in patients with AF recurrence after failed PVAI.
Section snippets
Patient population
Twenty consecutive patients undergoing first-time PVAI for symptomatic, drug-refractory AF (group 1) and twenty consecutive patients undergoing repeat-PVAI for late AF recurrences beyond 2 months (group 2) were studied. Only patients with symptomatic paroxysmal or persistent AF were included. All patients had AF that was refractory to at least one antiarrhythmic medication. Patients with prior open-heart cardiac surgery or permanent AF were excluded from the study. All patients gave written
Baseline characteristics
Of the 40 patients studied in groups 1 and 2, most were male (n = 2, 70%) with an average age of 54 ± 11 years. AF was paroxysmal in 30 (75%) patients and persistent in 10 (25%)—14/20 (70%) of group 1 patients and 16/20 (80%) group 2 patients had paroxysmal AF. Mean AF duration preablation was 5.9 ± 4.0 years. Patients had failed 2.2 ± 0.6 antiarrhythmic medications before ablation. Structural heart disease was present in 14 (35%) patients and included hypertensive heart disease (n = 8),
Main findings
This study demonstrates that in patients undergoing a first-time, ICE-guided PVAI procedure, vagal responses can be easily and reliably induced by AG stimulation in predictable anatomical locations in the LA. More importantly, these vagal responses are always eliminated by the standard PVAI lesion set, without specifically targeting these sites. This observation suggests that the success of PVAI in curing AF may, in part, be due to the elimination of these AG inputs in the LA. Alternatively,
Conclusions
Standard ICE-guided PVAI eliminates vagal responses induced by AG stimulation. Vagal responses during ablation do not correlate with vagal responses induced by AG stimulation. Vagal responses with AG stimulation are not seen in patients presenting for repeat PVAI despite clinical recurrence of AF.
References (17)
- et al.
Triggered firing in pulmonary veins initiated by in vitro autonomic nerve stimulation
Heart Rhythm
(2005) - et al.
Rapid and stable re-entry within the pulmonary vein as a mechanism initiating paroxysmal atrial fibrillation
J Am Coll Cardiol
(2005) - et al.
Feasibility study of endocardial mapping of ganglionated plexuses during catheter ablation of atrial fibrillation
Heart Rhythm
(2006) - et al.
Shortening of fibrillatory cycle length in the pulmonary vein during vagal excitation
J Am Coll Cardiol
(2006) - et al.
Gross and microscopic anatomy of the human intrinsic cardiac nervous system
Anat Rec
(1997) - et al.
Differing sympathetic and vagal effects on atrial fibrillation in dogs: role of refractoriness heterogeneity
Am J Physiol
(1997) - et al.
The atrial arrhythmia syndrome of vagal origin
Archives des maladies du coeur et des vaisseaux
(1978) - et al.
Spatial distribution and frequency dependence of arrhythmogenic vagal effects in canine atria
J Cardiovasc Electrophys
(2000)
Cited by (0)
- a
Atul Verma is supported by a fellowship award from the Heart and Stroke Foundation of Canada and is currently with Southlake Regional Health Centre, Newmarket, Ontario, Canada.