Abstract and Introduction
Abstract
Cerebrogenic control of cardiac function is well recognised and acute neurological events, including epileptic seizures, may cause a disturbance of cardiac function even in the absence of significant cardiac structural or electrophysiological abnormalities. Sudden unexpected death in epilepsy (SUDEP) is a major cause of mortality in patients with epilepsy. Cardiac dysrhythmias are a potential cause of SUDEP. Patients with epilepsy may be predisposed to developing arrhythmias due to a number of factors including chronic autonomic dysfunction, effects of anti-epileptic medication and a common genetic susceptibility. Future work should include the evaluation of inter-ictal and ictal electrophysiological, cardiorespiratory and metabolic variables in a large population of patients, including in specific syndromes, to further establish the pathophysiological mechanisms of SUDEP. A key aim is to stratify the risk of SUDEP for an individual patient and, ideally, identify potential therapeutic targets.
Introduction
Anatomical and functional connections between the brain and heart in both health and disease have long been established. Cardiac arrhythmias and ST segment changes have been observed with acute intracerebral events such as sub-arachnoid haemorrhage or cerebrovascular accidents[1] and, more recently, the interaction of the heart and brain in patients with epilepsy has been the subject of intense scrutiny. This has been driven by the publication of a number of important studies that have documented the frequent occurrence of cardiac rhythm changes during epileptic seizures,[2,3] and the lack of a clear pathophysiological mechanism for sudden unexpected death in epilepsy (SUDEP), an unexplained cause of death for over 500 patients with epilepsy in the UK each year. The study by Chaila and colleagues lends support to the now fairly well-established thesis that disturbed cerebral electrical activity during an epileptic seizure may cause transient cardiac arrhythmias (see pages 245–8). It is important to note, however, that although small series observational studies are helpful in raising awareness of this poorly understood entity, unfortunately, they have little capacity to inform the debate about possible mechanisms, risk factors and preventative measures.
There has always been a degree of clinical overlap between cardiology and neurology, and, more specifically, epileptology. Patients with episodes of collapse are frequently referred to either cardiologic or neurologic services and the correct diagnosis is often elusive. Misdiagnosis is common and possibly affects up to 20 to 30% of adults with a diagnosis of epilepsy.[4,5] For example, when 74 patients previously diagnosed with epilepsy were investigated with tilt-table testing, prolonged electrocardiogram (ECG) monitoring, blood pressure and ECG-monitored carotid sinus massage, an alternative cardiologic diagnosis was found in 31 (41.9%) of patients, including 13 taking anti-epileptic medication.[6] In addition to an isolated cardiologic or epileptic basis for an episode of collapse, there exists the phenomenon of cerebrogenic cardiac arrhythmias, which further confounds the diagnostic process (figure 1).
Figure 1.
Standard electroencephalograph (EEG) recording from a patient with focal epilepsy and recurrent seizures characterised by sudden onset of déjà vu, a rising epigastric sensation followed by loss of awareness and then collapse with marked facial pallor. The EEG shows right-sided rhythmic epileptic activity (most easily seen in the RsSph electrode trace) followed several seconds later by a 10–12 second period of cardiac asystole (electrocardiogram [ECG trace – bottom red line). Anti-epileptic medication was commenced and a permanent pacemaker was fitted and she has remained well with occasional déjà vu but no episodes of collapse or loss of consciousness
Br J Cardiol. 2010;17(5):223-229. © 2010 Medinews (Cardiology) Limited
Cite this: Epilepsy and the Heart - Medscape - Sep 01, 2010.
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