title: Comments on the article by Ribeiro et al. 'Enhanced parasympathetic activity in Chagas' disease still stands in need of proof': definitions and biases.
abstract: It has been hypothesized that impaired cardiac autonomic function in chagasic subject carriers of anti-muscarinic type 2 antibodies (Anti-M2) is a consequence of tonic stimulation (enhancement) of M2 receptors, thus damping high frequency spontaneous heart rate fluctuations. However, expected reduction in baseline average heart rate response as a consequence of M2 receptors stimulation has not been confirmed, imposing a query on current hypothesis for explaining autonomic impairment in Chagas' disease. In this context, possible explanations for the lack of heart rate reduction in the setting of chronic muscarinic stimulation in Chagas' disease have been discussed, based on current knowledge. Among possible factors implicated, stands out: i) spontaneous heart rate recovery after chronic vagal stimulation, ii) simultaneous anti-M2 and anti-beta 1 adrenergic receptors antibodies environments, iii) underlying cardiac function as assessed by both mechanical and humoral indexes, iv) age, v) immune status. Rigorous experimental settings may be necessary to mechanistically demonstrate eventually the association between agonistic anti-M2 environments and reduced autonomic modulation of the heart, in both humans and animal models, associated with short term and long term singular average resting heart rate balance secondary to parasympathetic stimulation.
authors.forename: Paulo Roberto
authors.initials: PR
authors.lastname: Benchimol-Barbosa
mesh_terms: D014355:Chagas Disease / Q000503:physiopathology*; D006801:Humans; D010275:Parasympathetic Nervous System / Q000502:physiology*