Key result
AF tissue exhibits ~56% shorter ligament of Marshall automatic cycle lengths under isoproterenol vs normal tissue.
Why the study?
The mechanism of adrenergic atrial tachyarrhythmia and the role of the ligament of Marshall in this arrhythmia were unclear.
Does the ligament of Marshall serve as a source of adrenergic atrial tachyarrhythmia in canine models?
Does the ligament of Marshall serve as a source of adrenergic atrial tachyarrhythmia in canine models?
The ligament of Marshall is richly innervated by sympathetic nerves and serves as a source of isoproterenol-sensitive focal automatic activity that can trigger atrial fibrillation.
Answers are grounded in this paper and cite their sources.
LOM ablation may suppress adrenergic AF triggers in canine models; leaves open translation to human ablation strategies.
BACKGROUND: The mechanism of the adrenergic atrial tachyarrhythmia is unclear. We hypothesize that the ligament of Marshall (LOM) is sensitive to adrenergic stimulation and may serve as a source of the adrenergic atrial tachyarrhythmia. METHODS AND RESULTS: We performed computerized mapping studies in isolated-perfused canine left atrial tissues from normal dogs (n=9) and from dogs with chronic atrial fibrillation (AF) induced by 10 to 41 weeks of rapid pacing (n=3). Before isoproterenol, spontaneous activity occurred in only one normal tissue (cycle length, CL >1300 ms). During isoproterenol infusion, automatic rhythm was induced in both normal tissues (CL=578+/-172 ms) and AF tissues (CL=255+/-29 ms, P<0.05). The origin of spontaneous activity was mapped to the LOM. In the AF tissues, but not the normal tissues, we observed the transition from rapid automatic activity to multiple wavelet AF. Ablation of the LOM terminated the spontaneous activity and prevented AF. Immunocytochemical studies of the LOM revealed muscle tracts surrounded by tyrosine hydroxylase-positive (sympathetic) nerves. CONCLUSIONS: We conclude that the LOM is richly innervated by sympathetic nerves and serves as a source of isoproterenol-sensitive focal automatic activity in normal canine atrium. The sensitivity to isoproterenol is upregulated after long-term rapid pacing and may contribute to the development of AF in this model.
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Doshi et al. (1999) studied Adrenergic atrial tachyarrhythmia (n=12). Isoproterenol infusion vs. Before isoproterenol / Normal tissues was evaluated on Automatic rhythm cycle length during isoproterenol infusion (p=<0.05). During isoproterenol infusion, automatic rhythm originating from the ligament of Marshall was faster in AF tissues compared to normal tissues (cycle length 255+/-29 ms vs 578+/-172 ms, P<0.05).
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