Tachycardia during seizures in ambulatory EEG-ECG monitoring: a retrospective cohort study

Sinus tachycardia during seizures is commonly reported in inpatient video-EEG monitoring, often with high prevalence estimates. These data are derived from selected populations under controlled conditions. We examined clinically documented tachycardia prevalence and determinants in a large retrospective ambulatory EEG-ECG cohort.

Methods: Clinically documented tachycardia during electrographically confirmed seizures was analyzed from finalized ambulatory EEG-ECG reports, with explicitly documented non-sinus tachyarrhythmias identified separately. The analysis was limited to tachycardia documented during seizures and did not include systematic peri-ictal arrhythmia analysis. Sinus tachycardia was defined as heart rate >100 bpm in adults, and age-adjusted thresholds for those <18. Associations with seizure type, duration, and patient-level factors were examined.

Reports were analyzed from 1368 patients with 6177 EEG-confirmed seizures. Tachycardia was clinically reported in 2065/6177 (33.4%) of seizures and 769/1368 (56.2%) of patients. Most tachycardia events were sinus/presumed sinus, however 7/2065 seizures with tachycardia were explicitly documented non-sinus tachyarrhythmias. It was more frequent in focal than generalized seizures (39.1% vs 24.4%) and was associated with longer seizure duration (median 61 s vs 18 s). Younger age and female sex were associated with tachycardia, though the age effect was modest. Medication effects were not robust after correction. Marked within-patient variability was observed: 30.5% had tachycardia in all seizures, 25.7% in some, and 43.8% in none.

In ambulatory monitoring, clinically documented sinus tachycardia occurs in one third of seizures, substantially lower than some inpatient estimates. Clinically documented ictal sinus tachycardia is associated with seizure duration, is more common in focal seizures, and demonstrates marked variability within individuals.