Authors :
Debra Moore-Hill, MD MPH – Wellstar MCG Heatlh
Danielle Weiss, MD – Wellstar MCG Heatlh
Hunter Smith, DO – Wellstar MCG Heatlh
Liam Goldman, MD – Wellstar MCG Heatlh
Leila Hill, AS – Wellstar MCG Health
Mingyu Li, MD – Wellstar MCG Heatlh
Chasitie McIntosh, NP – Wellstar MCG Heatlh
Presenting Author: Brandon Pope, MD PhD – Wellstar MCG Health
Luca Debs, MD – Wellstar MCG Health
Anthony Murro, MD – Wellstar MCG Heatlh
Fernando Vale, MD – Wellstar MCG Heatlh
Rationale: Vagus nerve stimulator (VNS) therapy utilizes 3 programming modes: fixed interval stimulation (NM), heart rate change stimulation (auto stimulation mode, AS) and on-demand stimulation (magnetic mode). Current VNS guidelines are too general and may fail to reflect best programming practices. This study surveyed practitioners and identified current titration and target setting practices. We hypothesize that a survey would identify areas for improving VNS programming.
Methods: Epilepsy VNS practitioners received an IRB approved, anonymous, voluntary survey, containing no protected health information, using a Microsoft Form (
https://forms.office.com/r/pWmafpJN55) by web link and QR code. We provided the survey at the American Epilepsy Society Meeting (12/3/2023, Orlando FL), by email invitation and by social media. We analyzed 12/3/2024 to 4/6/2024 data.
Results: Sixty responded; we retained 58 respondents, excluding 2 respondents who did not program VNS. The respondents were US-practicing (n=45, 78%), epileptologists (n=43, 74%) programming VNS devices in 50 patients or less per two years (n=39, 67%), and respondents who do VNS training or program VNS independently (n=49, 84%). Large variations in NM, AS, duty cycle (DC) and timing settings occurred (Figures 1 and 2). The median initial and maximum target NM output was 1-1.25mA (n=18, 31%) and 2-2.5mA (n=23, 40%) respectively. Respondents set initial AS at 40% heart rate increase (n=19, 33%) and final AS set at 20% heart rate increase (n=19, 33%). Most (n=47, 81%) achieve final VNS programming settings at or before 40 weeks, and most (n=37, 64%) identify VNS non-responders at 13-36 months of programming.
Conclusions: Some respondents (14%) underdose treatment identifying the maximum NM current target as 0.5-1.375 mA (2, 3). Most use a fraction of the available DC range as 23% reported optimum final DC at 16% (30 seconds on/3 minutes off) or 25% (30 second on/1.8 minutes off). The AS is often titrated as 41% report reaching AS threshold target at 13-24 months of treatment. Many (33%) set a final AS threshold of 20%. Other respondents use AS sub-optimally (1), 48% reported 30-70% AS final output target, while 17% were unsure about the optimal final AS threshold target. On achieving optimum settings, many respondents (42%) identified non-responders at 13-24 months of treatment; some respondents (3%) identified VNS non-responders early after 3-6 months of treatment, far before reaching final NM output targets.
Despite the limitations of this survey, these findings suggest a knowledge gap between current clinical practice and optimal dosing therapy. Clinical effectiveness may be compromised by lack of therapy optimization. These findings identify areas for practitioner education that could improve VNS therapy outcomes.
VNS Therapy System Epilepsy Physician's Manual, LivaNova USA, Inc (2023).
Tzadok M, et al Epilepsy Behavior (2022). Rapid Titration of VNS Therapy Reduces Time-To-Response in Epilepsy. Epilepsy & Behavior 134;108861
Fahoum F et al (2022). VNS parameters for clinical response in epilepsy. Brain Stimulation 15; 814-821.
Funding: This is an unfunded study.