p.23 抽出テキスト

.......................................................................................................................................................................... pharmacological stress, identifies a group at higher risk of developing AVB.115122

The efficacy of EPS for the diagnosis of syncope is highest in patients with sinus bradycardia, bifascicular block, and suspected tachycardia,62 and lowest in patients with syncope, a normal ECG, no structural heart disease, and no palpitations. Therefore, EPS is preferred over ILR in patients with syncope who have a high pre-test probability for significant conduction disease (e.g. abnormal ECG, BBB, ischaemic heart disease, or scar-related cardiomyopathy). For patients with a low pre-test probability (no structural heart disease, normal ECG), ILR is preferred over EPS. EPS is also preferred when there is a high likelihood that another syncopal episode will be dangerous or life-threatening and an immediate diagnosis is likely if EPS is performed. A negative EPS does not exclude an arrhythmic syncope, and further evaluation is warranted. Approximately one-third of patients with a negative EPS in whom an ILR is implanted develop AVB at follow-up.123

5 Cardiac pacing for bradycardia

and conduction system disease

5.1 Pacing for sinus node dysfunction

SND, also known as sick sinus syndrome, comprises a wide spectrum of sinoatrial dysfunctions, ranging from sinus bradycardia, sinoatrial block, and sinus arrest to bradycardiatachycardia syndrome.124,125 An additional manifestation of SND is an inadequate chronotropic response to exercise, reported as chronotropic incompetence.

5.1.1 Indications for pacing 5.1.1.1 Sinus node dysfunction In general, pacing for asymptomatic SND has never been shown to affect prognosis, as opposed to pacing for AVB. Therefore, SND can be considered as an appropriate indication for permanent pacing only when bradycardia due to SND is symptomatic.126 Patients with SND may manifest symptoms attributable to bradyarrhythmia and/or symptoms of accompanying atrial tachyarrhythmias in the bradycardiatachycardia form of the disease. Symptoms may be present either at rest or at the end of the tachyarrhythmic episode (conversion pause also named pre-automaticity pause), or develop during exercise, and may range from mild fatigue to light-headedness, dizzy spells, near-syncope, to syncope. Dyspnoea on exertion may be related to chronotropic incompetence. Syncope is a common manifestation of SND and has been reported in 50% of patients who receive a pacemaker for SND.127

Establishing a correlation between symptoms and bradyarrhythmia is a crucial step in decision-making. However, age, concomitant heart disease, and other comorbidities may pose difficulties in establishing a clear causeeffect relationship between SND and symptoms. The effect of cardiac pacing on the natural history of bradyarrhythmias was evaluated in non-randomized studies undertaken at the beginning of the pacemaker era, which suggested a symptomatic improvement with cardiac pacing.128131 This was confirmed by one randomized controlled trial (RCT)14 in which 107 patients (aged 73 ± 11 years) with symptomatic SND were randomized to no treatment, oral theophylline, or dual-chamber (DDD) rate-responsive pacemaker therapy. In this study, the occurrence of syncope and HF was lower in the pacemaker group during a follow-up of 19 ± 14 months. In patients presenting with exercise intolerance in whom chronotropic incompetence has been identified, the usefulness of cardiac pacing is uncertain, and the decision to implant a pacemaker in such patients should be made on a case by case basis. In some cases, symptomatic bradyarrhythmias may be related to transient, potentially reversible, or treatable conditions (section 4, Table 7). In such cases, correction of these factors is required, whereas permanent pacing is not indicated. In clinical practice, it is crucial to distinguish physiological bradycardia (due to autonomic influences or training effects) from inappropriate bradycardia that requires permanent cardiac pacing. For example, sinus bradycardia, even when it is 4050 b.p.m. while at rest or as slow as 30 b.p.m. while sleeping, particularly in trained athletes, could be accepted as a physiological finding that does not require cardiac pacing. Asymptomatic bradycardia (due to either sinus pauses or AVB episodes) is not uncommon and warrants interpretation in the clinical context of the patient: in healthy subjects, pauses >2.5 s are uncommon, but this per se does not necessarily constitute a clinical disorder; asymptomatic bradyarrhythmias are common in athletes.132 In the absence of published trials, no recommendations for bradycardia detected in asymptomatic patients can be made. On the other hand, in patients investigated for syncope in whom asymptomatic pause(s) >6 s due to sinus arrest are eventually documented, pacing may be indicated. Indeed, such patients constituted a small minority of those included in an observational study and a randomized trial on pacing in reflex syncope.133,134 In patients presenting with sleep-related asymptomatic intermittent bradycardia (sinus bradycardia or AVB), sleep apnoea and rapid eye movement sleep-related bradycardia should be considered as possible causes.

Recommendations for electrophysiology study

Recommendations Classa Levelb

In patients with syncope and bifascicular block, EPS should be considered when syncope remains unexplained after non-invasive evaluation or when an immediate decision about pacing is needed due to severity, unless empirical pacemaker implantation is preferred (especially in elderly and frail patients).115121 IIa B In patients with syncope and sinus bradycardia, EPS may be considered when non-invasive tests have failed to show a correlation between syncope and bradycardia.113,114 IIb B

EPS = electrophysiology study. aClass of recommendation. bLevel of evidence. ESC 2021 Downloaded from academic.oup.com/eurheartj/article/42/35/3427/6358547 by guest on 07 October 2026