Nerve sprouting induced by radiofrequency catheter ablation in dogs

OBJECTIVES The purpose of this study was to test the hypothesis that radiofrequency (RF) catheter ablation results in cardiac nerve sprouting. BACKGROUND Nerve sprouting plays a role in cardiac arrhythmogenesis. Whether or not nerve sprouting occurs after RF catheter ablation is unclear. METHODS We performed RF catheter ablation in the right atrium (RA) and right ventricle (RV) in 10 dogs, which then were sacrificed in 2 hours (acute group, n = 5) or 1 month (chronic group, n = 5). Seven normal dogs were used as control. Immunohistochemical staining for growth-associated protein 43 (GAP-43) was performed to measure growing (sprouting) nerves. RESULTS A significant increase of GAP-43 immunoreactive nerve fiber density was observed at the RA ablation sites in 2 hours (4,410 +/- 1,379 mum(2)/ mm(2)) and in 1 month (2,948 +/- 666 mum(2)/Mm(2)) after ablation compared to controls (1,377 +/- 471 mu/mm(2), P = .0001). At remote sites (>2 cm away from ablation sites) of RA, RF ablation also resulted in robust nerve sprouting in both the acute group (5,846 +/- 3241 mum(2)/mm(2)) and the chronic group (6,030 +/- 2226 mum(2) /mm(2)). RF ablation in the RV did not increase nerve density at the ablation sites, but nerve density was increased at remote sites in 2 hours (1,345 +/- 451 mum(2)/mm(2,) P = .0136) that was reduced down to the normal control level (722 +/- 337 mum(2)/mm(2)) in 1 month. CONCLUSIONS Nerve sprouting occurred within 2 hours after RF ablation in both the RA and RV and persisted for at least 1 month in the RA but not the RV. The increased GAP-43(+) nerve densities developed at both the ablation and the remote sites. (C) 2004 Heart Rhythm Society. All rights reserved.