Seizure-like episodes and EEG abnormalities in patients with long QT syndrome

The congenital long QT-syndrome (cLQTS) is characterized by ventricular arrhythmias, syncope and sudden cardiac death. Many LQTS genes are also expressed in the brain and emerging evidence suggest that cardiac channelopathies can also cause epilepsy. The aim of the study is to explore evidence of epilepsy and/or EEG abnormalities in a cohort with a genotyped diagnosis of LQT1 or LQT2.

Adult patients were randomly selected from the outpatient clinic and a random sample of healthy controls were recruited from the general population. Ictal semiology was explored in symptomatic patients. A 1 h 64-channel awake EEG was performed and analyzed by visual assessment. Brain connectivity was quantified by Directed Transfer Function (DTF) from the current source density estimate within the theta band (4-7 Hz).

Fifteen patients with LQT1, 20 with LQT2 and 20 controls were included. Seventy-one % of the patients reported loss of consciousness (LOC); 44% in combination with convulsions. EEG was abnormal in 34% of patients and 10% of controls (p < 0.05). Two patients had epileptiform or sharp activity. The fronto-parietal DTF connectivity was significantly altered in patients compared to controls (LQT1 p = 2.2 × 10-6, LQT2 p = 0.044).

Seizure-like episodes and EEG abnormalities were common in our cohort with cLQTS patients. However, we could not find firm evidence of epilepsy. Our findings reinforce the notion that cLQTS is a cardiocerebral channelopathy. Correct classification of seizures may be challenging to the clinician, but of vital importance for patients.