Autonomic neural remodeling of the pulmonary vein-left atrium junction in a prolonged right atrial pacing canine model.

BACKGROUND

No evidence has been presented to show whether autonomic neural remodeling occurs in pulmonary vein-left atrium (PV-LA) junction and what an important role it may play in AF. This study aims to find out these issues in a prolonged rapid atrial pacing canine model.

METHODS

Twelve healthy mongrel dogs were randomly divided into two groups, six in each: the paced group underwent rapid right atrial pacing at 400 beats per minute for 4 weeks, and the control group was not paced. The effective refractory period (ERP) of left superior pulmonary vein-left atrium (LSPV-LA) junction in all animals was determined immediately after 4 weeks. Tissues were removed from 1 cm around all PV-LA junctions. Immunohistochemical staining and western blotting were performed to examine the expression of tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT).

RESULTS

Compared with the control group, ERP of LSPV-LA junction of the paced group was significantly shortened ([83.33 ± 16.33] ms vs [111.67 ± 20.41] ms, P < 0.05). Spontaneous atrial fibrillation developed in two animals in the paced group, but in none of the control group. Immunohistochemistry showed that the average density and heterogeneity of both TH- and ChAT-positive nerves at LSPV-LA junction in the paced group were significantly higher compared to the control group (P < 0.01). Western blotting showed that the expression of TH and ChAT at four PV-LA junctions in the paced group also increased markedly compared with the control group (P < 0.01).

CONCLUSION

Autonomic neural remodeling did exist in PV-LA junction after prolonged atrial pacing, which may contribute to the initiation of atrial fibrillation and be significant in its treatment by radiofrequency catheter ablation.