Evaluation of Cardiac Repolarization Indices in Epilepsy Patients Treated with Carbamazepine and Valproic Acid

Epilepsy and long-term risk of arrhythmias

BACKGROUND AND AIMS

Previous evidence has mainly supported transient changes in cardiac function during interictal or peri-ictal phases in people with epilepsy, but the long-term risk of cardiac arrhythmias is poorly described. This study aimed to assess the long-term association of epilepsy with cardiac arrhythmias, considering the potential role of genetic predisposition and antiseizure medications (ASMs) in any associations observed.

METHODS

This population-based study evaluated UK Biobank data for individuals recruited between 2006 and 2010. Cox proportional hazards models and competing risk models were used to examine the association of epilepsy history with the long-term incidence risk of cardiac arrhythmias and arrhythmias subtypes. Polygenic risk scores (PRS) were calculated to investigate the effect of genetic susceptibility. The role of ASMs was also evaluated by integrating observational and drug target Mendelian randomization (MR) evidence.

RESULTS

The study included 329 432 individuals, including 2699 people with epilepsy. Compared with those without epilepsy, people with epilepsy experienced an increased risk of all cardiac arrhythmias [hazard ratio (HR) 1.36, 95% confidence interval (CI) 1.21-1.53], atrial fibrillation (HR 1.26, 95% CI 1.08-1.46), and other cardiac arrhythmias (HR 1.56, 95% CI 1.34-1.81). The associations were not modified by genetic predisposition as indicated by PRS. Competing and sensitivity analyses corroborated these results. Individuals with epilepsy using ASMs, especially carbamazepine and valproic acid, were at a higher risk for cardiac arrhythmias. This observation was further supported by drug target MR results (PSMR < .05 and PHEIDI > .05).

CONCLUSION

This study revealed the higher risk of cardiac arrhythmias persists long term in people with epilepsy, especially among those using carbamazepine and valproic acid. These findings highlight the need for regular heart rhythm monitoring and management in people with epilepsy in order to reduce the risk of further cardiovascular complications.

Characterization in Inhibitory Effectiveness of Carbamazepine in Voltage-Gated Na+ and Erg-Mediated K+ Currents in a Mouse Neural Crest-Derived (Neuro-2a) Cell Line

Carbamazepine (CBZ, Tegretol®) is an anticonvulsant used in the treatment of epilepsy and neuropathic pain; however, several unwanted effects of this drug have been noticed. Therefore, the regulatory actions of CBZ on ionic currents in electrically excitable cells need to be reappraised, although its efficacy in suppressing voltage-gated Na+ current (INa) has been disclosed. This study was undertaken to explore the modifications produced by CBZ on ionic currents (e.g., INa and erg-mediated K+ current [IK(erg)]) measured from Neuro-2a (N2a) cells. In these cells, we found that this drug differentially suppressed the peak (transient, INa(T)) and sustained (late, INa(L)) components of INa in a concentration-dependent manner with effective IC50 of 56 and 18 μM, respectively. The overall current-voltage relationship of INa(T) with or without the addition of CBZ remained unchanged; however, the strength (i.e., ∆area) in the window component of INa (INa(W)) evoked by the short ascending ramp pulse (Vramp) was overly lessened in the CBZ presence. Tefluthrin (Tef), a synthetic pyrethroid, known to stimulate INa, augmented the strength of the voltage-dependent hysteresis (Hys(V)) of persistent INa (INa(P)) in response to the isosceles-triangular Vramp; moreover, further application of CBZ attenuated Tef-mediated accentuation of INa(P)'s Hys(V). With a two-step voltage protocol, the recovery of INa(T) inactivation seen in Neuro-2a cells became progressively slowed by adding CBZ; however, the cumulative inhibition of INa(T) evoked by pulse train stimulation was enhanced during exposure to this drug. Neuro-2a-cell exposure to CBZ (100 μM), the magnitude of erg-mediated K+ current measured throughout the entire voltage-clamp steps applied was mildly inhibited. The docking results regarding the interaction of CBZ and voltage-gate Na+ (NaV) channel predicted the ability of CBZ to bind to some amino-acid residues in NaV due to the existence of a hydrogen bond or hydrophobic contact. It is conceivable from the current investigations that the INa (INa(T), INa(L), INa(W), and INa(P)) residing in Neuro-2a cells are susceptible to being suppressed by CBZ, and that its block on INa(L) is larger than that on INa(T). Collectively, the magnitude and gating of NaV channels produced by the CBZ presence might have an impact on its anticonvulsant and analgesic effects occurring in vivo.

Corrected QT interval and QT dispersion in temporal lobe epilepsy

Background

Cardiac arrhythmias are expected among patients with epilepsy due to the effect of anti-epileptic drugs. Temporal lobe epilepsy also causes autonomic seizures that may affect heart rhythm. Prolongation of the corrected QT interval and QT dispersion is a risk factor for cardiac arrhythmia.

Objectives

We aimed to assess corrected QT interval and QT dispersion in patients with epilepsy and if there is a difference between patients with temporal epilepsy versus non-temporal epilepsy.

Methods

This study was conducted on 100 patients (50 patients with temporal epilepsy and 50 patients with non-temporal epilepsy) and 50 age- and sex-matched healthy controls. They underwent a prolonged (6 to 24 h) 22 channel computerized electroencephalogram monitor with a 10–20 system. QT dispersion, QT interval, and corrected QT interval (using Bazett’s formula) were calculated.

Results

This study showed significantly higher QT dispersion and corrected QT interval in patients with epilepsy when compared to the age- and sex-matched control group (P < 0.001, P < 0.001). Also, the corrected QT interval and QT dispersion were significantly higher in temporal epilepsy patients when compared to the non-temporal group (P < 0.001, P < 0.001).

Conclusion

Corrected QT interval and QT dispersion are higher in epileptic patients and more among temporal epilepsy patients in comparison to non-temporal epilepsy patients.