Cardiac autonomic modulation in drug-resistant epilepsy patients after vagus nerve stimulation therapy

The positive effect of vagus nerve stimulation (VNS) in patients with drug-resistant epilepsy is considered to be mediated by the afferent pathways of the vagus nerve, but the efferent pathways may influence the cardiac autonomic activity.

To assess the effects of VNS on cardiac autonomic modulation in epilepsy patients, over three months of neurostimulation.

Linear and non-linear heart rate variability (HRV) analysis can provide information on the sympathovagal balance and reveal particularities of the central control of the autonomic cardiovascular function.

Using Biopac Acquisition System, we analysed HRV parameters in resting condition and during sympathetic and parasympathetic activation tests in five patients with drug-resistant epilepsy, who underwent VNS procedure.

During the sympathetic and vagal activation tests, all five patients presented normal responses of cardiac autonomic activity, reflected in RMSSD, HFnu and LF/HF dynamics in both HRV evaluations. No bradycardia, cardiac arrhythmia or orthostatic hypotension was registered during the two evaluations.

Our results indicate that VNS appears not to alter the cardiac autonomic function after three months of neurostimulation. HRV analysis is a useful tool for evaluating cardiac autonomic modulation in epilepsy patients during VNS therapy.

Patients with decreased HRV should be periodically monitored. Cardiac changes in patients with epilepsy are important because of the additional risk of arrhythmias mediated through the autonomic dysfunction.