Cardiac effects of repeated focal seizures in rats induced by intrahippocampal tetanus toxin: Bradyarrhythmias, tachycardias, and prolonged interictal QT interval / JGR. Jefferys, A. Ashby-Lumsden, TA. Lovick,
Jefferys, John G R Department of Pharmacology, Oxford University, Oxford, UK. School of Clinical & Experimental Medicine, The University of Birmingham, Birmingham, UK. School of Biomedical Engineering, Purdue University, West Lafayette, Indiana. Department of Physiology, 2nd Medical School, Motol, Charles University, Prague, Czech Republic. Ashby-Lumsden, Alexander Department of Pharmacology, Oxford University, Oxford, UK. School of Clinical & Experimental Medicine, The University of Birmingham, Birmingham, UK. Lovick, Thelma A School of Biomedical Engineering, Purdue University, West Lafayette, Indiana. School of Physiology, Pharmacology and Neuroscience, The University of Bristol, Bristol, UK.
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.