Vagus nerve stimulation reduces cardiac electrical instability assessed by quantitative T-wave alternans analysis in patients with drug-resistant focal epilepsy
Schomer AC, Nearing BD, Schachter SC, Verrier RL.
Epilepsia. 2014 Dec;55(12):1996-2002.
https://doi.org/10.1111/epi.12855.
Did you know that the risk of sudden cardiac death in epilepsy patient is 3-fold higher than in the general population and 4.5-fold higher than sudden unexpected death in epilepsy?¹ To describe the cardiac risk in patients with epilepsy, the concept of the “epileptic heart” was proposed by Verrier et al. in 2020, defined as “a heart and coronary vasculature damaged by chronic epilepsy as a result of repeated surges in catecholamines and hypoxemia leading to electrical and mechanical dysfunction”.²
Multiple studies have examined the efficacy of vagus nerve stimulation (#VNS) therapy in reducing the risk of cardiac mortality for patients with drug-resistant epilepsy (#DRE). Thus, for the next theme, we will put emphasis on publications evaluating VNS therapy outcomes related to the epileptic heart.
In 2014, Schomer et al. conducted a study examing the changes in T-wave alternans (#TWA; a proven noninvasive marker for the risk of sudden cardiac death in patients with cardiovascular disease), and heart rate variability (#HRV) induced by VNS treatment in patients with focal DRE (n=9, age: 29-63). The study included patients who underwent VNS implantation for the first time or battery change (Demipulse M103) at a single center. It was the first study to report the possibility of VNS reducing the abnormally high level of TWA in DRE patients with focal seizures, suggesting a potential cardioprotective function of VNS for DRE patients:
Seven patients had >20 years of epilepsy history. No patients had a history of cardiac disease. No antiseizure medication change were made during the study. The ambulatory electrocardiogram (#ECG) was recorded 24 h before VNS implantation in 6 patients and at 7.6 weeks post-implantation in all 9 patients.
Main findings:
➤All 6 patients who underwent ambulatory ECG recording before VNS implantation showed abnormally high TWA levels. Their TWA levels were significantly reduced after VNS treatment (p=0.02).
➤TWA levels were reduced to the normal range in 4 out of 6 patients (67%), indicating a lower risk for sudden cardiac death.
➤VNS dose was significantly associated with the reduction of TWA levels in leads V1 (p<0.05) and V5 (p<0.01).
➤Low-frequency HRV and low- to high-frequency HRV ratios were reduced by 60% (p=0.05) and 32% (p=0.025), suggesting an improved parasympathetic dominance by the change of autonomic balance.
Considering that the effects of VNS tend to improve over time, studies with a longer follow-up duration, and a larger cohort of patients, should be conducted to determine the plausible continuation of the downregulation of TWA levels. Moreover, further studies examining the effects of VNS dosing titration on the epileptic heart should be considered.
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Link to the article: https://lnkd.in/eauVfu2D
