Introduction: Heart rate decrease during epileptic seizures is rare and should be considered in patients with unusual or refractory episodes of syncope or in patients with a history suggestive of both epilepsy and syncope. We systematically reviewed the literature to better understand the clinical signs and risk factors of ictal heart rate decreases. Material and methods: We performed a literature-search on “ictal bradycardia” and “ictal asystole” in Pubmed and added papers from the references and personal archives. Articles relating to animal studies, seizures without ictal decrease of heart rate, cases without simultaneous electroencephalography (EEG) and electrocardiography (ECG), convulsive syncopes, or cases with bradycardia before seizure onset and articles written in other languages than English, Dutch, German, French, or Spanish were excluded. Full texts of the remaining articles were screened for cases of ictal bradycardia or ictal asystole. Cases were selected on the basis of a self-designed quality score. The relationship of RR wave interval of at least 5 s, signs of syncope, and EEG signs of ischemia were analyzed with chi-square test and identifying 95% confidence intervals. Results: Ictal bradycardia and ictal asystole predominantly occurred during focal seizures with loss of awareness (proportion in the combined group of bradycardia and asystole (p1 + 2) = 0.85) in people with mainly left lateralized (p1 + 2 = 0.64; p = 0.001) temporal lobe seizures (p1 + 2 = 0.91). Seizures with ictal asystole typically started with a heart rate decrease. During ictal asystole in the majority of cases, not only the clinical signs of syncope occurred (change of proportion (Δp) = 0.67; 95% CI: 0.48–0.86; p < 0.0001), i.e., interrupting the seizure semiology, but also the characteristic EEG signs of ischemia (Δp = 0.50; 95% CI: 0.26–0.74; p < 0.001). We found a statistically significant relation between signs of syncope and EEG signs of ischemia (Δp = − 0.37; 95% CI: (− 0.64)–(− 0.10); p < 0.01) but not between duration of asystole (5 s) and either signs of syncope (Δp = − 0.36; 95% CI: (− 0.77)–0.05; p = 0.03) or EEG signs of ischemia (Δp = − 0.37; 95% CI: (− 1.07)–0.33; p = 0.16). Conclusion: In the ictal bradycardia syndrome, signs of syncope disrupt the semiology of ongoing seizures and are associated with EEG signs of brain ischemia and the duration of the cardiac arrhythmia.