Heart rate and blood pressure variability in patients with myasthenia gravis.

This cross-sectional case control study included subjects aged between 18 and 65 years with diagnosis of myasthenia gravis (MG) in Osserman's Stage I and Stage IIa and those in remission with positive and negative acetylcholine receptor antibody (AChRAb). They were evaluated for heart rate variability (HRV) and other conventional autonomic functions. Patients with co-morbidities that can affect autonomic nervous system were excluded. Repetitive nerve stimulation test (RNST), nerve conduction test, AChRAb assay, and computerized tomography (CT) of chest were done in all the patients. All patients of MG who fulfilled the inclusion criteria had a minimum drug-free period of 6 h which was followed by HRV and other conventional tests. Thirty subjects fulfilling study criteria and an equal number of age and gender-matched healthy subjects were enrolled as controls. Autonomic function tests revealed significant changes in HRV (both time and frequency domain) parameters suggestive of parasympathetic deficiency as well as shifting of sympathovagal balance towards raised sympathetic tone. With regards to conventional autonomic function tests, there was statistically significant decrease in values of heart rate-based tests as well as blood pressure-based test (isometric handgrip test) in study group compared with controls, again indicative of significant parasympathetic deficiency and minimal sympathetic deficiency. We conclude that in MG, cholinergic transmission is affected more diffusely than previously thought.