Abnormal electroencephalograms in patients with long QT syndrome

Abstract

The long QT syndrome (LQTS) is an inherited cardiac channelopathy associated with syncope and sudden cardiac death due to ventricular arrhythmias. It is most frequently caused by potassium channel mutations. Potassium channels are also expressed in brain tissue and play an important role in idiopathic epilepsies. Recent reports have indicated that related potassium channel mutations may coexpress as concomitant epilepsy and LQTS. The purpose of this study was to explore cerebral activity by means of EEG recordings in individuals with LQTS related to potassium channel mutations. Seventeen individuals with confirmed LQTS related to potassium channel mutations (11 LQT1 and 6 LQT2) were prospectively studied with 21-channel electroencephalography (EEG) LQTS -related symptoms, comorbidity, medication, and QTc (12-lead ECG) were recorded. Sixteen healthy individuals previously studied with EEG served as a control group. All EEGs were reviewed by two independent neurophysiologists. EEG recordings were abnormal in 12 of 17 patients (71%) in the LQTS group, whereas abnormalities were present in only 2 of 16 healthy controls (13%; P <.01). In the LQTS group, all abnormal EEGs showed a combination of theta activity and sharp waves. Two patients showed additional delta activity. None of the patients had definite epileptic activity (spikes, spike waves). Abnormal electrical cerebral activity was identified more frequently in subjects with LQTS secondary to a potassium channel mutation compared with healthy controls. This result indicates a possible link between cardiac and cerebral channelopathy.