Electrocardiographic and oximetric changes during partial complex and generalized seizures

Significant autonomic changes occur during seizures and may be related to sudden unexplained death in epilepsy (SUDEP). Accordingly, we performed a study to determine the prevalence of heart rate, QTc, and oximetric changes during seizures and analyzed their association with SUDEP risk factors. We analyzed 218 seizures from 76 patients. Ictal sinus tachycardia occurred in 57% of seizures and was associated with ≥3 failed AEDs (p=0.001), generalized seizures (p<0.001), and normal brain MRI (p=0.04). Ictal sinus bradycardia was rare, occurring in 2% of seizures. Ictal bradycardia was associated with seizure clustering (p=0.028) and reported history of ≥50 seizures/month (p=0.01). Depending on the correction formula utilized for calculating QTc, clinically significant ictal QTc prolongation (≥460ms for children ≤13 years, ≥470ms for males age >13, and ≥480ms for females age >13) occurred in 4.8-16.2% of seizures, while ictal QTc prolongation ≥500ms occurred in 2.9-16.2%. Ictal QTc shortening ≤340ms was observed in 3.8-4.8% of seizures. Ictal hypoxemia occurred in 25% of seizures and was associated with normal MRI (p=0.01), longer seizure duration (p=0.049), and ictal tachycardia (p=0.003). Such findings may have implications for understanding the pathogenesis of SUDEP.