The presence of dysautonomia in different subgroups of myasthenia gravis patients.

To analyze the presence of autonomic dysfunction in different subgroups of myasthenia gravis (MG) patients. Standard cardiovascular reflex tests according to Ewing, spectral and time domain analysis of heart rate variability (HRV) at rest were assessed in 27 patients with thymoma-associated acetylcholine receptor (AChR)-positive MG, 25 AChR-positive MG patients without thymoma and 23 patients with muscle-specific tyrosine kinase (MuSK) MG. All patients were compared to the healthy controls, matched for sex and age. In the group of AChR-positive MG patients with thymoma, hand grip (p < 0.05), orthostasis (p < 0.05), breathing test (p < 0.05) and Valsalva maneuver (p < 0.01) were more often pathological than in the controls. Analysis of the spectral domain of HRV showed increased low-frequency (p < 0.05) and decreased high-frequency component (p < 0.05). Time domain parameters of HRV and baroreflex sensitivity (BRS) at rest were significantly reduced (p < 0.01). In the patients with AChR MG without thymoma, Valsalva maneuver test was more often pathological (p < 0.05) and higher rate of supraventricular extrasystoles (p < 0.01) was registered than in the healthy controls. In the patients with MuSK-positive MG, hand grip and Valsalva maneuver tests were more often pathological than in the controls (p < 0.05). Low-frequency component of the spectral domain of HRV (p < 0.05) and the frequency of cardiac arrhythmia were increased. BRS at rest was significantly lower in patients compared to the controls (p < 0.01). We determined the presence of autonomic failure in all subgroups of MG patients. Since autonomic dysfunction can lead to cardiac arrhythmias and even sudden death, it is of major importance to be aware of this association and to properly diagnose and treat these patients.