Recurrent syncope with seizure-like features: the role of emergency monitoring in revealing intermittent AV block

BACKGROUND: Recurrent syncope with seizure-like stiffening may mimic epilepsy or neurological disorders, and when routine tests are repeatedly normal, intermittent arrhythmia can be easily overlooked. CASE PRESENTATION: We report a case of a 65-year-old man with hypertension, hyperuricaemia, dyslipidaemia, and asthma who experienced recurrent syncopal episodes over one month. He presented several times to emergency departments and tertiary hospitals. Neurological and cardiovascular investigations-including brain MRI, echocardiography, coronary angiography, laboratory tests, and a previous Holter ECG-were consistently unremarkable. The initial diagnosis was hypertensive crisis based on marked post-event blood pressure surges, which was later recognized as a secondary phenomena rather than the primary cause of syncope. On the index admission, continuous emergency monitoring captured a sinus arrest of ~ 17 s with absent arterial pulse waveform, followed by bradyarrhythmia. Post-event blood pressure spiked to 220/110 mmHg. A repeat Holter ECG confirmed intermittent Mobitz II and complete AV block with asystole up to 18.6 s. EEG, performed during this admission to exclude epilepsy, was normal. A dual-chamber permanent pacemaker was implanted with complete resolution of symptoms (Shen et al, Circulation 136(5):e60-e122, 2017; Kusumoto et al, Circulation 140(8): e382-e482, 2019; Brignole et al, Eur Heart J 39(21):1883-1948, 2018). CONCLUSION: This case demonstrates how intermittent AV block may masquerade as seizure or hypertensive crisis, underlining the critical role of emergency department monitoring and prolonged ECG recording in recurrent unexplained syncope.