Relationship between autonomic innervation in crista terminalis and atrial arrhythmia

The crista terminalis (CT) is known to initiate and maintain atrial arrhythmia, and is affected by autonomic tone, but the underlying mechanisms are poorly understood. This study sought to study the relation between autonomic innervation in CT and atrial arrhythmia.

Thirty adult canines were used in the present study. Tissues of the CT and the pectinate muscles (PM) were obtained from 10 dogs for electrophysiology studies. Furthermore, tissues of the superior CT, the inferior CT, and the PM were obtained from 10 dogs for immunohistochemistrical studies. Anti-growth-associated protein 43 (GAP43), anti-tyrosine hydroxylase (TH), and choline acetyltransferase (ChAT) antibodies for immunocytochemical staining of cardiac nerves were performed to test the densities of autonomic nerve. Densities of I K,ACh in the superior CT, the inferior CT, and the PM cells were measured by patch clamp in the other 10 dogs.

With the pacing cycle length decreased, the amplitude of delayed after depolarization (DAD) increased and DAD-induced triggered activity was induced in the CT but not in PM with norepinephrine administration. GAP-43 and TH-positive nerves in the superior CT and the inferior CT were all significantly higher than in the PM (GAP-43: 6,250 +/- 1,928 vs 1,247 +/- 747, 2,855 +/- 1,579 vs 1,247 +/- 747; TH: 3,140 +/- 1,240 vs 690 +/- 720, 1,210 +/- 980 vs 690 +/- 720; P < 0.01). Furthermore, the GAP-43 and TH-positive nerves in the superior CT were higher than in the inferior CT. However, there were no significant differences in ChAT-positive nerves and I K,ACh in the superior CT, the inferior CT, and the PM.

The higher densities of adrenergic nerve in the CT play an important role in the genesis of atrial arrhythmia.