Preoperative heart rate variability in relation to surgery outcome in refractory epilepsy

Background: Epilepsy patients may have an impaired autonomic cardiac control, which has been associated with an increased incidence of sudden unexpected death among people with epilepsy (SUDEP). The risk of SUDEP is particularly high among epilepsy surgery candidates with refractory epilepsy. This risk seems to be reduced after successful surgery but whether this is an effect of surgery or reflects pre-existing differences between good and poor responders is under debate. Methods: We used spectral analysis to analyze prospectively heart rate variability (HRV) preoperatively in 21 consecutive patients with temporal lobe epilepsy who were planned for epilepsy surgery. The presurgical HRV based on ambulatory 24 hours EKG recordings was analyzed in relation to seizure control at 1 year after surgery. Results: Patients had significantly lower SD of RR-intervals, total power, very low frequency power and low frequency power than matched healthy controls. Patients with good outcome of surgery (Engel class I; n = 11) did not differ from their controls while those with poor outcome ( Engel class II-IV; n = 10) had significantly lower power in all domains than those with a favorable outcome. Conclusions: Measurements of heart rate variability preoperatively indicate that patients with a poor outcome of surgery have a more pronounced impairment of sympathetic as well as parasympathetic cardiac control than those with good outcome. Reduced heart rate variability may be associated with an increased risk of sudden unexpected death among people with epilepsy (SUDEP). Good surgery candidates may a priori have a lower risk of SUDEP.