Clinical aspects of device-detected arrhythmias

INTRODUCTION: Cardiac implantable electronic devices (CIEDs) enable continuous monitoring of the heart rhythm. CIEDs constitute a unique opportunity for detecting arrhythmias, as the duration of cardiac monitoring is of the utmost importance for the detection rate. The CIED population consists mostly of patients from older age categories where risk factors for atrial fibrillation (AF) are common. A dual-chamber device can detect and store episodes with a high atrial rate, i.e. atrial high-rate episodes (AHREs). AHREs confirmed to be AF, atrial flutter or focal atrial tachycardia are termed subclinical AF. Both terms refer to patients with no symptoms attributed to AF, with no previous diagnosis of clinical AF. These episodes of device-detected AF are associated with increased risk of ischaemic stroke, although the risk seems to be lower than in patients with documented clinical AF, and the benefit of oral anticoagulation (OAC) treatment in this population has not been established. Patients presenting with syncope represent a diagnostic challenge. Initial evaluation can provide the underlying mechanism in up to half of the patients. However, the mechanism remains unexplained in many patients, and long-term electrocardiogram (ECG) monitoring with an implantable loop recorder (ILR) enables ECG recording at the time of syncope recurrence, which can reveal the underlying mechanism. The aim of this thesis is to highlight different aspects of arrhythmias diagnosed with CIEDs, both from a diagnostic and a therapeutic point of view. More specifically, it aims to describe the incidence of subclinical AF/AHREs in a pacemaker population, along with its OAC treatment, and the incidence of ischaemic stroke and vascular dementia. In addition, it will explore the role of the baseline 12-lead ECG in predicting the syncope mechanism during ILR monitoring, and whether age and gender impact the evaluation before the implantation and subsequent diagnostic yield of the ILR. Finally, the