Published online Jun 26, 2014. doi: 10.4330/wjc.v6.i6.502
Revised: April 11, 2014
Accepted: May 16, 2014
Published online: June 26, 2014
Processing time: 183 Days and 17.6 Hours
AIM: To conduct the first systematic test of the hypothesis that modulation of cardiac vagal tone is impaired in Lyme disease.
METHODS: The response of cardiac vagal tone to respiratory modulation was measured in 18 serologically positive Lyme disease patients and in 18 controls.
RESULTS: The two groups were matched in respect of age, sex, body mass, mean arterial blood pressure, mean resting heart rate and mean resting cardiac vagal tone. The mean maximum cardiac vagal tone during deep breathing in the Lyme disease patients [11.2 (standard error 1.3)] was lower than in the matched controls [16.5 (standard error 1.7); P = 0.02].
CONCLUSION: Respiratory modulation of cardiac vagal tone is impaired in Lyme disease, which suggests that Lyme disease may directly affect the vagus nerve or the brainstem.
Core tip: Given that immune dysfunction, postural orthostatic tachycardia syndrome, fatigue, cognitive dysfunction, orthostatic palpitations, syncope, and stress, which may occur in Lyme disease, are associated with parasympathetic activity and reduced modulation of cardiac vagal tone, we hypothesized that modulation of cardiac vagal tone is impaired in this disease. This was confirmed in our study of 18 patients and 18 matched controls. Cardiac vagal tone is reflexly generated through arterial baroreceptor stimulation, by the afferents of the latter facilitating cardiac vagal motoneuron discharge relaying through interneurons in the nucleus tractus solitarius, implying that Lyme disease may directly affect the vagus or brainstem.