Long-Term Effects of Box Isolation on Sympathovagal Balance in Atrial Fibrillation

Abstract

Background: Complete isolation of the posterior left atrium, including all pulmonary veins (box isolation), is a feasible and safe atrial fibrillation (AF) treatment method. Data on long-term effects of box isolation on autonomic function, however, remain limited. Methods and Results:A total of 92 patients (paroxysmal AF, n=76; persistent AF, n=16) undergoing box isolation with non-contact mapping were studied. Twenty-four-hours ambulatory electrocardiograms and transthoracic echocardiography were done at baseline and after 2 days, and at 3, 6 and 12 months. Autonomic functions were evaluated by means of heart rate variability (HRV). During a mean follow up of 16±5 months, no AF episodes were detected in 76 patients while AF recurred in 16. Significant long-term HRV attenuations were observed in all patients without AF recurrence, but not in those with AF recurrence. In patients without AF recurrence, the natural logarithm (Ln) high-frequency (HF) decreased significantly from 5.5±1.3 ms 2 (before) to 4.2±0.9 ms 2 (after 12 months, P<0.001) and the ratio of the low-frequency to HF power increased significantly from 2.4±2.0 (before) to 3.4±2.3 (after 12 months, P=0.05). LnHF was significantly lower in patients without than in those with AF recurrence during the 12-month period after ablation. Cardiac function improved significantly in patients without AF recurrence after box isolation. Conclusions:Changes in the sympathovagal balance with box isolation may contribute to AF prevention. (Circ J 2010; 74: 1096 - 1103

Denervation as a Common Mechanism Underlying Different Pulmonary Vein Isolation Strategies for Paroxysmal Atrial Fibrillation: Evidenced by Heart Rate Variability after Ablation

“…Multivariate analysis revealed that HF and LF/HF were independent predictors of PAF recurrence. Yamaguchi et al [19] performed box isolation on AF patients, which is a procedure characterized by the complete isolation of four PVs and a larger LA area compared with routine CPVI. After a followup of 16 ± 5 months, significant HRV attenuation was associated with a greater suppression of AF recurrence.…”

Recent Insights Into the Role of the Autonomic Nervous System in the Creation of Substrate for Atrial Fibrillation

“…PV ectopic foci appear to be at least partially modulated by autonomic signaling, with sympathetic stimulation with isoproterenol being frequently utilized to “bring out” these triggers in patients undergoing ablation for AF. Clinical studies have demonstrated a change in heart rate variability after PV ablation 25 . Several investigators have also noted Bezold-Jarisch-like or ‘vagal’ reflexes during radiofrequency ablation of the PVs.…”

“…As alluded to earlier, much of the data supporting the involvement of the autonomic nervous system in patients with AF comes from noninvasive measures of autonomic tone such as heart rate variability (HRV) 25 . It must be remembered, however, that HRV is a measure of autonomic modulation on the sinus node, and does not reliably quantify sympathetic and parasympathetic activity.…”

Left atrial posterior wall isolation affects complex fractionated atrial electrograms in persistent atrial fibrillation

“…Furthermore, parasympathetic denervation may have contributed to a decrease in CFAE areas. Since parasympathetic fibers and muscarinic receptors are preferentially located in the posterior wall of the left atrium, LAPWI attenuates parasympathetic nerve activities and increases sympathovagal balance . Parasympathetic activity causes the release of acetylcholine, which acts predominantly on M2 receptors to activate the G‐protein‐activated potassium current (I KACh ) and shorten the duration of the action potential and effective refractory period .…”