John G R Jefferys1,2,3,4, Alexander Ashby-Lumsden1,2, Thelma A Lovick3,5. 1. Department of Pharmacology, Oxford University, Oxford, UK. 2. School of Clinical & Experimental Medicine, The University of Birmingham, Birmingham, UK. 3. School of Biomedical Engineering, Purdue University, West Lafayette, Indiana. 4. Department of Physiology, 2nd Medical School, Motol, Charles University, Prague, Czech Republic. 5. School of Physiology, Pharmacology and Neuroscience, The University of Bristol, Bristol, UK.
Abstract
OBJECTIVE: To determine electrical changes in the heart in a chronic, nonstatus model of epilepsy. METHODS: Electrocorticography (ECoG) and electrocardiography (ECG) of nine animals (five made epileptic by intrahippocampal injection of tetanus neurotoxin (TeNT) and four controls), are monitored continuously by radiotelemetry for up to 7 weeks. RESULTS: Epileptic animals develop a median of 168 seizures, with postictal tachycardias reaching a mean of 487 beats/min and lasting a mean of 661 seconds. Ictal changes in heart rate include tachycardia and in the case of convulsive seizures, bradyarrhythmias resembling Mobitz type 1 second-degree atrioventricular block; notably the P-R interval increased before block. Postictally, the amplitude of T wave increases. Interictally, QT dependence on RR is modest and conventional QT corrections prove ineffective. Interictal QT intervals, measured at a heart rate of 400 bpm, increased from 65 to 75 ms, an increase dependent on seizure incidence over the preceding 10-14 days. SIGNIFICANCE: Repeated seizures induce a sustained tachycardia and increase in QT interval of the ECG and evoke arrhythmias including periods of atrioventricular block during Racine type 4 and 5 seizures. These changes in cardiac function may predispose to development in fatal arrhythmias and sudden death in humans with epilepsy. Wiley Periodicals, Inc.
OBJECTIVE: To determine electrical changes in the heart in a chronic, nonstatus model of epilepsy. METHODS: Electrocorticography (ECoG) and electrocardiography (ECG) of nine animals (five made epileptic by intrahippocampal injection of tetanus neurotoxin (TeNT) and four controls), are monitored continuously by radiotelemetry for up to 7 weeks. RESULTS:Epileptic animals develop a median of 168 seizures, with postictal tachycardias reaching a mean of 487 beats/min and lasting a mean of 661 seconds. Ictal changes in heart rate include tachycardia and in the case of convulsive seizures, bradyarrhythmias resembling Mobitz type 1 second-degree atrioventricular block; notably the P-R interval increased before block. Postictally, the amplitude of T wave increases. Interictally, QT dependence on RR is modest and conventional QT corrections prove ineffective. Interictal QT intervals, measured at a heart rate of 400 bpm, increased from 65 to 75 ms, an increase dependent on seizure incidence over the preceding 10-14 days. SIGNIFICANCE: Repeated seizures induce a sustained tachycardia and increase in QT interval of the ECG and evoke arrhythmias including periods of atrioventricular block during Racine type 4 and 5 seizures. These changes in cardiac function may predispose to development in fatal arrhythmias and sudden death in humans with epilepsy. Wiley Periodicals, Inc.