Study of cardiac autonomic function in drug-naive, newly diagnosed epilepsy patients

Background. Epilepsy is associated with ictal autonomic dysfunction which may extend into the inter-ictal period. Antiepileptic drugs have often been blamed for cardiac autonomic dysfunction in epilepsy patients. In this study we have investigated cardiac autonomic parameters in order to evaluate autonomic functions of drug-naive epilepsy patients. Method. Twenty drug-naive patients (15 males and 5 females) with epilepsy, and an equal number of age and gender matched controls, were evaluated for short-term resting heart rate variability and conventional cardiovascular autonomic measurements. Results. The mean age of patients was 29.30 +/- 9.80 yrs (17-55 yrs), mean age at seizure onset was 19.70 +/- 9.15 yrs (3-40 yrs) and mean length of time since last seizure was 5.60 +/- 7.00 days (1-30 days). While there was no difference in the resting heart rate or conventional autonomic test parameters, time domain heart rate variability measurements showed a decreased percentage of R-R intervals of less than 50 ms and root mean square of R-R intervals in patients, when compared to controls. Frequency domain parameters showed a decreased total power (patients: 1,796.58 +/- 1,052.45 ms(2); controls: 2,934.23 +/- 1,767.06 ms(2), p = 0.008). Parameters indicative of decreased vagal tone, i.e. decreased high frequency power and increased low to high frequency ratio (patients: 1.69 +/- 0.94; controls: 1.14 +/- 0.64, p = 0.045), were observed among patients compared to controls. Conclusion. Subtle but definite cardiac autonomic dysfunction, especially in vagal tone, was identified in drug-naive, new-onset epilepsy patients. Seizures can cause long-term and often progressive cardiac autonomic dysfunction which may be independent of concomitant antiepileptic drugs.