Cardiac autonomic dysfunctions in chronic refractory epilepsy

Sudden unexplained death is an important cause of mortality in patients with epilepsy and cause for this is not fully understood. One of the explanations is autonomic dysfunction (AD). Studies of AD in chronic refractory epilepsy are very few in the literature.

To evaluate cardiovascular autonomic functions in chronic refractory epilepsy patients.

Seventy-three patients (31.5+/-9.8 years, M:F::45:28) with chronic intractable epilepsy attending the "refractory epilepsy clinic" at a tertiary referral center (National Institute of Mental Health and Neuro Sciences (NIMHANS), Bangalore, India) were enrolled. Age and gender matched healthy subjects were recruited as controls. Heart rate (HR) and blood pressure (BP) at rest and HR response after deep breathing, Valsalva maneuver, postural change and BP response to postural change and isometric work were recorded. AD was graded as early if one of HR or BP, definite if two or more HR and severe if two or more HR with BP based tests were detected to be abnormal.

The mean age at onset and duration of epilepsy was 12.4+/-8.5 years and 19.02+/-9.07 years, respectively. Twenty-three (31.5%) patients of refractory epilepsy had early involvement while 25 patients (primary generalized: 8, partial: 17) had Definite AD, and 16 (primary generalized: 4, partial: 12) had severe autonomic dysfunction. ANCOVA results showed expiration-inspiration, standing maximum:minimum ratio, standing 2 min systolic and isometric diastolic BP of the dysfunction group significantly differ compared to the control group. Patients with longer duration of epilepsy (23.2 years) had more severe dysfunction (p < 0.05) than patients with relatively shorter duration (17.5 years) of epilepsy. Antiepileptic drugs (AED) used did not show any significant role on autonomic functions in this study.

This is the first study from India to evaluate autonomic functions in refractory epilepsy patients. Autonomic dysfunction was noted in 56.3% of patients. Anticonvulsants used were not associated with AD. Longitudinal controlled studies with 'newly diagnosed' epilepsy patients will enhance further understanding about the role of autonomic system in epilepsy.