Abstracts

Rationale: Heart rate variability (HRV) is a useful tool in the evaluation of the autonomic nervous system and decreased HRV measures have been found to be negative prognostic markers of cardiovascular mortality. Autonomic effects on heart rate have been well documented during seizures, and some of these changes have been implicated as plausible mechanisms of SUDEP. This study compares peri-ictal HRV in patients with partial epilepsy and psychogenic non-epileptic seizures. Methods: This is a retrospective study of patients evaluated at our epilepsy monitoring unit during 2009. Subjects with a diagnosis of partial epilepsy or psychogenic nonepileptic seizures (PNES) were included. Subjects with PNES were used as the control group. Time-domain measures of HRV were calculated during the pre-ictal and ictal periods using ten-second electrocardiogram recordings. The values for the standard deviation of all RR intervals (SDNN) and the root-mean-square successive difference (r-MSSD) were obtained using the Kubios 2.0 software. Differences between age, gender, pre-ictal HRV and ictal HRV were assessed using a Wilcoxon rank-sum test. P-values < 0.05 were regarded as statistically significant. Results: Twenty-two patients were included, 12 patients had PNES and 10 subjects had partial epilepsy (5 with temporal lobe epilepsy: TLE). No significant differences (p? 0.05) in age or gender were found between the two study groups. During the pre-ictal or ictal period, no significant differences in HRV were found between the subjects with partial epilepsy and PNES. However, during the ictal period, subjects with TLE had significantly lower measures of SDNN (p<0.045) and r-MSSD (p<0.018) when compared to subjects with PNES. Conclusions: In this study, we found decreased HRV measures in seizures originating from the temporal lobe compared to psychogenic events confirmed by video EEG. Our results suggest that decreased ictal HRV in patients with TLE is not solely due to psychological apprehension towards an upcoming seizure. Significant changes in HRV may be seen more frequently in TLE than other types of partial epilepsy due to the proximity of the temporal lobe to the insular cortex, which may exert influences on cardiovascular autonomic control. At present, it is unknown whether decreased HRV measures are a risk factor for SUDEP in patients with intractable epilepsy. This deserves further investigation and prospective studies, since the development of useful clinical markers for the detection of patients at risk of SUDEP may help guide therapeutic interventions in the future. We are actively recruiting patients for this study.