Vagal denervation and reinnervation after ablation of ganglionated plexi

Abstract

Objective: Surgical ablation of ganglionated plexi has been proposed to increase efficacy of surgery for atrial fibrillation. This experimental canine study examined electrophysiologic attenuation and recovery of atrial vagal effects after ganglionated plexi ablation alone or with standard surgical lesion sets for atrial fibrillation.

Methods: Dogs were divided into 3 groups: group 1 (n = 6) had focal ablation of the 4 major epicardial ganglionated plexi fat pads, group 2 (n = 6) had pulmonary vein isolation with ablation, and group 3 (n = 6) had posterior left atrial isolation with ablation. All fat pads were ablated. Sinus and atrioventricular interval changes during bilateral vagosympathetic trunk stimulation were examined before and both immediately and 4 weeks after ablation. Vagally induced effective refractory period changes and mean QRST area changes (index of local innervation) were examined in 5 atrial regions.

Results: Sinus and atrioventricular interval changes and heart rate variability decreased immediately after ablation, but only sinus interval changes were restored significantly after 4 weeks in all groups. Ablation-modified vagal effects on effective refractory period or QRST area changed heterogeneously in groups 1 and 2. In group 3, regional vagal effects were attenuated extensively postablation in both atria. Posterior left atrial isolation with ablation incrementally denervated the atria. In the long term, vagal stimulation increased QRST area changes relative to control values in all groups. Heart rate variability was also assessed.

Conclusions: Ganglionated plexi ablation significantly reduced atrial vagal innervation. Restoration of vagal effects at 4 weeks suggests early atrial reinnervation.

2010 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.

Figures

Figure 1

Surgical ablation sets in each group. RAA, right atrial appendage; SVC, superior vena cavae; IVC, inferior vena cavae; LAA left atrial appendage.

Figure 2

A: Calculation of change in QRST area for unipolar electrographic analysis. Stim, Stimulation. B: Five atrial regions in QRST analysis. RAA, right atrial appendage; LAA, left atrial appendage; SVC, superior vena cavae; IVC, inferior vena cavae; SRA, superior right atrium; IRA, inferior right atrium; SLA, superior left atrium, ILA, inferior left atrium, PLA, posterior left atrium.

Figure 3

Change in sinus and atrioventricular (AV) interval in Group A, B, and C. *P < 0.05 (for control vs VST stimulation)

Figure 4

Change in heart rate variability. SDNN, standard deviation of normal RR intervals; rMSSD, root mean square of standard deviation; HF, high frequency power; LF, low frequency power.

Figure 5

Upper panel represents the atrial activation maps constructed from sinus rhythm without vagal stimulation (A), with vagal stimulation (B) pre-ablation, and sinus rhythm with vagal stimulation immediately post-ablation. Lower panel represents sinus activation maps without vagal stimulation (D) and with vagal stimulation (E) at 4 weeks in the same animal. The maps represent the lateral view in the right atrium. The asterisks indicate the earliest activation site in the right atrium. The atrial activation is shown with color coding at 10 ms increments. The numbers below the figure indicate the sinus interval time (ms) in the each activation. RAA, right atrial appendage; SVC, superior vena cavae; IVC, inferior vena cavae; TV, tricuspid valve; RPV, right pulmonary vein.

Figure 6

Mean QRST area change at 5 atrial regions pre-ablation, immediately post-ablation, and 4 weeks post-ablation. Significant increased area changes against control values was indicated by shading. (P<0.05)

Figure 7

Change in effective refractory period (ERP) at 5 atrial regions in Group 1, 2, and 3. RAA, right atrial appendage; RIA, right inferior atrium; LAA, left atrial appendage; LIA, left inferior atrium; LPA, left posterior atrium. *P<0.05.