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Pulmonary Vein Isolation and Cox-Maze IV Only Partially Denervate the Atria
S. C. Lall, K. V. Foyil, S. Sakamoto, R. K. Voeller, R. B. Schuessler, R. J. Damiano. Washington University School of Medicine, Saint Louis, MO,
Background
Bipolar radiofrequency ablation (RFA) has recently been used to replace the incisions and simplify the Cox-Maze procedure to surgically treat atrial fibrillation. In addition, pulmonary vein isolation using RFA has been proposed as an alternative to the complete Cox-Maze lesion set. The autonomic nervous system affects the electrophysiologic substrates responsible for atrial fibrillation. It is unclear what effect ablations lines used for pulmonary vein isolation and the Cox-Maze procedure have on the innervation of the myocardium and its response to autonomic stimuli. The aim of this study was to examine the effect of RFA on atrial sympathetic and parasympathetic innervation comparing pulmonary vein isolation and the complete Cox-Maze lesion set.
Methods
In twelve acute canine models, right and left vagosympathetic trunks (VST) and right and left stellate ganglia were isolated and decentralized. Each nerve was stimulated before any bipolar RFA lesions, after pulmonary vein isolation, and after completion of the Cox-Maze IV lesion set. Atropine (0.08 mg/kg IV bolus, 0.04 mg/kg IV each hour) was given to block the parasympathetic response in six dogs and nadolol (1 mg/kg IV bolus) was given to block the sympathetic response in the remaining six dogs. Changes in heart rate (HR) and atrial ventricular (AV) interval were compared. Results are reported as mean values ± standard error, with (*) denoting significant changes (p<0.05.)
Results
In controls, parasympathetic effects were seen with right and left VST stimulation (see Table.) In the sympathetic control model, effects on HR were seen with all nerves except the left stellate and effects on AV interval were seen with stimulation of all four nerves. Upon pulmonary vein isolation, parasympathetic effects on HR with left VST stimulation and on AV conduction with right VST stimulation were eliminated. After pulmonary vein isolation, sympathetic effects on HR and AV interval seen with stimulation of the left VST and left stellate were eliminated, as well as the effects on HR with stimulation of the right VST. Parasympathetic effects with stimulation of the left VST were eliminated after completing the Cox-Maze lesion set, but stimulation of the right VST still had parasympathetic effects on HR. The sympathetic effects after the Cox-Maze seen with stimulation of the right stellate were eliminated, but the right VST sympathetic effects were still seen.
Change in HR and AV Interval with Nerve Stimulation | Control Change in HR (bpm) | Control Change in AV Interval (ms) | Post Pulmonary Vein Isolation Change in HR (bpm) | Post Pulmonary Vein Isolation Change in AV Interval (ms) | Post Cox-Maze IV Change in HR (bpm) | Post Cox-Maze IV Change in AV Interval (ms) | | Parasympathetic Right VST | 22 ± 8.4* | 46 ± 9.9* | 15 ± 4.9* | 32 ± 14.4 | 4 ± 1.4* | 20 ± 10.4 | | Parasympathetic Right Stellate | 1 ± 0.8 | 1 ± 6.3 | 1 ± 1.2 | 7 ± 2.7 | 2 ± 0.7 | 3 ± 3.5 | | Parasympathetic Left VST | 25 ± 4.8* | 28 ± 9.2* | 6 ± 3.5 | 33 ± 11.3* | 3 ± 0.9 | 31 ± 15.8 | | Parasympathetic Left Stellate | 2 ± 0.9 | 13 ± 8.6 | 2 ± 1.0 | 10 ± 4.6 | 3 ± 0.9 | 8 ± 3.7 | | Sympathetic Right VST | 69 ± 15.2* | 35 ± 3.1* | 37 ± 13.7 | 27 ± 9.2* | 43 ± 6.0* | 31 ± 7.1* | | Sympathetic Right Stellate | 60 ± 9.4* | 20 ± 6.9* | 40 ± 12.1* | 22 ± 7.1* | 18 ± 14.0 | 9 ± 5.7 | Sympathetic
Left VST | 38 ± 7.1* | 14 ± 5.6* | 9 ± 6.4 | 12 ± 6.0 | 6 ± 9.4 | 8 ± 4.8 | Sympathetic
Left Stellate | 38 ± 20.1 | 20 ± 7.7* | 24 ± 17.0 | 16 ± 8.1 | 32 ± 23.3 | 6 ± 4.2 |
Conclusions
Sympathetic and parasympathetic innervation to the canine myocardium was disrupted by RFA lines. Although pulmonary vein isolation disrupted some sympathetic and parasympathetic innervation, the Cox-Maze lesion set shows more complete disruption of autonomic innervation. However, even after the complete Cox-Maze lesion set, residual effects on HR and AV conduction were seen with sympathetic and parasympathetic stimulation.
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