Patients with difficult-to-treat epilepsy ("refractory epilepsy") are at high risk of sudden death: sudden unexpected death in epilepsy (SUDEP). Cardiac arrhythmias are one of the possible causes of SUDEP. When monitoring in the hospital setting, the frequency of cardiac arrhythmias in people with epilepsy is low: 0,4%. However, when a subcutaneous implantable device (Reveal XT) is used to monitor heart rhythm continuously for an extended period of time, the frequency of clinically relevant arrhythmias appeared much higher in two small observational studies (n=19): 6-20%. The aim of this study is to analyze the frequency and underlying mechanism of cardiac arrhythmias in a larger group of 50 people with refractory epilepsy with Reveal XT. In the future, this may help us to identify those epilepsy patients at high risk of cardiac arrhythmias, so that we can timely institute preventive measures (e.g. pacemaker implantation).

Inclusion Criteria:

• Drug-resistant focal epilepsy: failure of adequate trials of two tolerated and appropriately chosen and used antiepileptic drug (AED) schedules (whether as monotherapies or in combination) to achieve sustained seizure freedom [16]
• ≥ 1 complex partial and/or generalized tonic clonic seizure/month as indicated by history taking
• If female, not pregnant
• Aged 18 to 60 years
• Able to undergo the study procedure as judged by the treating physician.

Exclusion Criteria:

• Clinical suspicion of seizure-induced asystole (e.g. seizures with sudden flaccid falls)
• Reveal implantation (either present or in the past)
• Known clinical relevant structural cardiac disease
• Hereditary syndromes that increase the risk of cardiomyopathy (e.g. Marfan's disease)
• ECG findings suggestive of arrhythmias without proper cardiac evaluation to in- or exclude this possibility. According to European Society of Cardiology (ESC) guidelines on syncope the following ECG findings will be used: bifascicular block and other intraventricular conduction abnormalities, asymptomatic inappropriate sinus bradycardia (<50 bpm), sinoatrial block or sinus pause ≥3s in the absence of negative chronotropic medications, non-sustained VT, pre-exited QRS complexes, prolonged or short QT interval, Brugada pattern, pattern suggestive of arrhythmogenic right ventricular cardiomyopathy.
• Pacemaker
• Use of beta blockers or other anti-arrhythmic/anti-arrhythmogenic medication
• Previous diagnosis of psychogenic non-epileptic seizures
• Patients who live alone and are not able to recall their seizures