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............................................ 4.3.6 Sleep evaluation Nocturnal bradyarrhythmias are common in the general population. In most circumstances, these are physiological, vagally mediated asymptomatic events, which do not require intervention.98100 Patients with sleep apnoea syndrome (SAS) have a higher prevalence of sleep-related bradycardia (both sinus and conduction system related) during apnoeic episodes.101,102 SAS-induced hypoxaemia is a key mechanism leading to an increased vagal tone and bradycardic rhythm disorders.101,102 Another rare mechanism of sleep-related bradycardia (usually in the form of prolonged sinus arrest) is rapid eye movement sleep-related bradycardia, unrelated to apnoea. This mechanism can also be diagnosed by polysomnography.103 Although most cases quoted in the literature have been treated with pacemakers, the evidence for this is scant, and there is no consensus on how to treat these patients.103 Treatment with continuous positive airway pressure (CPAP) alleviates obstructive sleep apnoea-related symptoms and improves cardiovascular outcomes. Appropriate treatment reduces episodes of bradycardia by 7289%,104 and patients are unlikely to develop symptomatic bradycardia at long-term follow-up.104106 Therefore, patients with asymptomatic nocturnal bradyarrhythmias or cardiac conduction diseases should be evaluated for SAS. If the diagnosis is confirmed, treatment of sleep apnoea with CPAP and weight loss can be effective in improving bradyarrhythmias occurring during sleep, and permanent pacing should be avoided. In patients with known or suspected SAS and symptomatic bradyarrhythmias not associated with sleep, a more complex assessment of the risks associated with bradyarrhythmias vs. the benefit of cardiac pacing is needed. 4.3.7 Tilt testing Tilt testing should be considered to confirm a diagnosis of reflex syncope in patients in whom this diagnosis was suspected but not confirmed by initial evaluation.62,107 The endpoint of tilt testing is the reproduction of symptoms along with the characteristic circulatory pattern of the reflex syncope. The methodology and classification of responses are described in section 4.2 in the Supplementary data and in Supplementary Figure 1. A positive cardioinhibitory response to tilt testing predicts, with high probability, asystolic spontaneous syncope; this finding is relevant for therapy when cardiac pacing is considered (see section 5.4). Conversely, the presence of a positive vasodepressor, a mixed response, or even a negative response does not exclude asystole during spontaneous syncope.62 4.4 Implantable monitors Patients with infrequent symptoms of bradycardia (less than once per month) need a longer duration of ECG monitoring. For these patients, the implantable loop recorder (ILR) is an ideal diagnostic tool given its capacity for prolonged monitoring (up to 3 years) and without the need for active patient participation (Table 8). In patients with unexplained syncope after the initial evaluation and infrequent symptoms (less than once a month), several studies have demonstrated a higher efficacy of initial ILR implantation compared with a conventional strategy. Many conditions diagnosed by ILR are bradycardia mediated.108112 For further discussion on the diagnostic roles of ILR and ambulatory ECG, and indications for their use, refer to the ESC Guidelines for the diagnosis and management of syncope.62 Recommendations for genetic testing Recommendations Classa Levelb Genetic testing should be considered in patients with early onset (age <50 years) of progressive cardiac conduction disease.c 65,97 IIa C Genetic testing should be considered in family members following the identification of a pathogenic genetic variant that explains the clinical phenotype of cardiac conduction disease in an index case.65 IIa C aClass of recommendation. bLevel of evidence. cProgressive cardiac conduction disease: prolonged P wave duration, PR interval, and QRS widening with axis deviation.96 ESC 2021 Recommendation for sleep evaluation Recommendation Classa Levelb Screening for SAS is recommended in patients with symptoms of SAS and in the presence of severe bradycardia or advanced AVB during sleep.101106 I C AVB = atrioventricular block; SAS = sleep apnoea syndrome. aClass of recommendation. bLevel of evidence. ESC 2021 Recommendation for tilt testing Recommendation Classa Levelb Tilt testing should be considered in patients with suspected recurrent reflex syncope.62 IIa B aClass of recommendation. bLevel of evidence. Recommendation for implantable loop recorders Recommendation Classa Levelb In patients with infrequent (less than once a month) unexplained syncope or other symptoms suspected to be caused by bradycardia, in whom a comprehensive evaluation did not demonstrate a cause, long-term ambulat ory monitoring with an ILR is recommended.108112 I A ILR = implantable loop recorder. aClass of recommendation. bLevel of evidence. ESC 2021 ESC 2021 ................................................................................................................................ Downloaded from academic.oup.com/eurheartj/article/42/35/3427/6358547 by guest on 07 October 2026