Researchers at Western General and Royal Hospital for Sick Children, Edinburgh, UK, measured the corrected QT interval before and during seizures in a prospective study of 39 children, 1 month-16 years of age, with various epilepsies. Of a total of 156 seizures 9 were generalized tonic-clonic (5 patients), 34 absences (6 patients), 12 tonic seizures (6 patients), 27 temporal lobe seizures (14 patients), 58 frontal lobe seizures (4 patients), and 16 subclinical seizures (4 patients). Corrected QT during total seizure data compared to total pre-seizure values showed a statistically significant difference (p<0.001). Bazett's formula used to compare QT values found that 21 seizures in 9 patients transiently increased their corrected QT beyond normal limits, with a maximum corrected QT of 512 ms during a right temporal lobe seizure. Significant lengthening of corrected QT cardiac repolarization time during some epileptic seizures may have a role in sudden unexplained death in epilepsy (SUDEP). [1]

COMMENT. Measurements of QT in individual patients may show lengthening during some seizures, as in this study, whereas mean QT values for grouped data may be normal, as reported in some previous studies. No evidence of QT prolongation was detected in patients receiving antiepileptic monotherapy or polytherapy in a pediatric group. [2]

Cardiac arrhythmias and Seizures. In a 2-year review of electrographically confirmed seizures in a pediatric epilepsy-monitoring unit, ictal cardiac arrhythmias occurred in 45% of 244 seizures (40% of the patients). Benign respiratory sinus arrhythmia was the most common arrhythmia (in 78% of seizures with arrhythmias and 70% of patients with arrhythmias). Potentially serious arrhythmias including irregular variable arrhythmias and abnormal QRS intervals were seen in 12% of all the patients. [3]

Enhanced QT shortening and persistent tachycardia after generalized seizures are reported in a study of 25 patients with medically refractory temporal lobe epilepsy undergoing presurgical investigation at Institute of Neurology, Queen Square, London, UK [4]. Secondarily GTCS led to higher peri-ictal heart rate (HR), persistent postictal tachycardia, and decreased postictal HR variability. Abnormal shortening of the corrected QT interval occurred in 17 patients, mainly with secondarily GTCS. Benign cardiac arrhythmias occurred in 14 patients and were independent of seizure type. Cardiac abnormalities occurring in epilepsy with GTCS may potentially facilitate sudden cardiac death (SUDEP).