Ictal heart rate changes and the effects of vagus nerve stimulation for patients with refractory epilepsy

Figures

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  Figure 1. The mechanism of action of VNS efficacy in patients with normal HR during seizures. Notes: The mechanical signals coming from patients with normal HR during seizures and the mechanical signals coming from patients with the activation of vagal afferents through VNS all possibly play a role to produce responses to VNS therapy. →↓↑: The arrows show the signals coming from patients upon the activation of vagal afferents through VNS; →↓↑: The bold arrows show the signals coming from patients with normal HR during seizures. Abbreviations: HR, heart rate; BP, blood pressure; ABR, arterial baroreflex; VNS, vagus nerve stimulation; X, vagal nerve; IX, glossopharyngeal nerve; NTS, nucleus of the tractus solitarius.

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  Figure 2. The mechanism of action of VNS efficacy in patients with IT during seizures. Notes: The mechanical signals coming from patients with IT during seizures and the mechanical signals coming from patients upon the activation of vagal afferents through VNS all possibly play a role to produce better responses to VNS therapy. →↓↑: The arrows show the signals coming from patients upon activation of vagal afferents through VNS; →↓↑: The bold arrows show the signals coming from patients with IT during seizures. Abbreviations: IT, ictal tachycardia; HR, heart rate; BP, blood pressure; ABR, arterial baroreflex; VNS, vagus nerve stimulation; X, vagal nerve; IX, glossopharyngeal nerve; NTS, nucleus of the tractus solitarius.

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  Figure 3. The mechanism of action of VNS efficacy in patients with IB during seizures. Notes: The mechanical signals coming from patients with IB during seizures may be insufficient to support the efficacy of VNS. If the action potential frequency coming from patients upon activation of vagal afferents through VNS is greater than the frequency coming from patients with IB during seizures, response from patients with IB during seizures may be less efficient than patients with normal HR. Conversely, if the action potential frequency coming from VNS is less than the frequency coming from seizure with IB, patients with IB during seizures may be inefficient to VNS therapy. →↓↑: The arrows show the signals coming from patients upon activation of vagal afferents through VNS; →↓↑: The bold arrows show the signals coming from patients with IB during seizures. Abbreviations: IB, ictal bradycardia; HR, heart rate; BP, blood pressure; ABR, arterial baroreflex; VNS, vagus nerve stimulation; X, vagal nerve; IX, glossopharyngeal nerve; NTS, nucleus of the tractus solitarius.