Abstracts

Rationale: Seizure-related cardiorespiratory changes have recently received much attention, largely due to their relationship with sudden unexpected death in epilepsy (SUDEP). However, they remain poorly understood. We investigate temporal dynamics in cardiac and respiratory function in convulsive and non-convulsive seizures. Methods: 70 consecutive patients with epilepsy who had ≥1 seizures recorded during inpatient video-EEG monitoring with concurrent polysomnography between February 2012 and May 2017 were included. Seizures were classified as convulsive (n=18) or non-convulsive (n=140). Different epochs were selected for each seizure: baseline (60 sec), ending ≥60 sec before seizure onset; preictal (60 sec), ending at seizure onset; ictal, extending from seizure onset to termination; postictal (300 sec), starting from seizure termination. Heart and respiratory rates, heart rate variability (HRV), and peripheral capillary oxygenation levels were assessed in each epoch. Cardiorespiratory measurements were averaged across seizures of the same type for each patient. Heart and respiratory rates were also continuously followed for up to 60 minutes from seizure termination to determine whether these measures returned to baseline. Results: There were no significant differences in baseline or preictal cardiorespiratory function between convulsive and non-convulsive seizures. Ictal tachycardia was seen in both convulsive and non-convulsive seizures, but was more pronounced in convulsive seizures (P=0.000; see e.g. Figure 1). The ictal respiratory rate was lower in convulsive seizures compared with non-convulsive seizures (P=0.001). The median postictal heart rate was higher in convulsive seizures than in non-convulsive seizures: 163.5 beats per minute (range 40.0-201.0) compared with 101.4 beats per minute (range 52.0-166.5; P=60 min after seizure termination. Notably, post-ictal HRV was higher in convulsive seizures with post-ictal generalized EEG suppression (n=12) compared to those without (n=6; P=0.03). Conclusions: Cardiorespiratory dysfunction is considerably more pronounced following convulsive seizures compared to non-convulsive seizures, which may explain why the former carry the greatest risk of SUDEP. Targeting mechanisms underpinning this dysfunction may potentially prevent the occurrence of SUDEP. Funding: TO receives funding from the National Health and Medical Research Council (NHMRC) Program Grant. TO, PK and SS receive funding from The Royal Melbourne Hospital Neuroscience Foundation. PP is supported by the Melbourne International Research Scholarship (MIRS) and the Melbourne International Fee Remission Scholarship (MIFRS) from the University of Melbourne.