Effects of chronic epilepsy on heart rate variability

BACKGROUND: Dysfunctional autonomic cardiac regulation is thought to be associated with high mortality in epileptic patients. OBJECTIVE: To explore changes in sympathetic and parasympathetic activities in epileptic patients with repetitive generalized tonic-clonic seizures by observing interictal heart rate. DESIGN, TIME AND SETTING: A case-control study was performed at the Buddhist Tzu Chi General Hospital from July 2006 to May 2009. PARTICIPANTS: A total of 30 patients, comprising 15 males and 15 females, who presented with chronic epilepsy and repetitive generalized tonic-clonic seizures according to International League Against Epilepsy guidelines (ILAE, 1989), were selected. In addition, 30 matched, healthy volunteers were selected as controls. METHODS: Lead I electrocardiogram was performed in the epilepsy and control groups for 5 minutes during a daytime interictal period. Frequency-domain analysis of heart rate variability was performed using fast Fourier transformation. MAIN OUTCOME MEASURES: Heart rate interval, high frequency (HF; 0.15-0.45 Hz) power, low frequency (LF; 0.04-0.15 Hz) power, and LF/(HF + LF) expressed in normalized units (LF%). RESULTS: Compared with the control group, the epilepsy group exhibited a significantly lower mean heart rate interval and HF power, but a significantly greater LF% (P < 0.01). There was no significant difference in LF power between the groups (P = 0.17). CONCLUSION: Patients with chronic epilepsy exhibited faster heart rates during interictal periods, which could contribute to higher sympathetic and lower parasympathetic activities.