Causes of Syncope:

g) *Syncope via autonomic failure:
i) Neuropathy with autonomic involvement
ii) Antihypertensives, esp. beta-blockers
iii) Surgical sympathectomy
iv) CNS autonomic failure: eg.primary autonomic failure, MSA, spinal cord lesion

Causes of *Collapse and Acute Decreased Conscious State. (* = collapse, as in sudden loss of consciousness). 1. Respiratory (O ...
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Profound Bradycardia

However, CTS (Chemical Thoracic Sympathectomy) in patients having high SDRR:SD sub [partial diffenrential] RR ratios can result in profound bradycardia.
Anesthesiology. 89(3):666-670, September 1998.
Hirose, Munetaka MD; Imai, Hiroto MD; Ohmori, Misako MD; Matsumoto, Yasunori MD; Amaya, Fumimasa MD; Hosokawa, Toyoshi
MD; Tanaka, Yoshifumi MD

The results of endoscopic sympathectomy deteriorate progressively from the immediate outcome

British Journal of Surgery ISSN 0007-1323

1999, vol. 86, no1, pp. 45-47 (12 ref.)