From the Guidelines
Brief Episodes of Bradycardia Causes
The primary causes of brief episodes of bradycardia are sinus node dysfunction (SND) and atrioventricular block, with the latter being further categorized into fixed or intermittent blocks 1.
- Sinus Node Dysfunction (SND): This can manifest as sinus bradycardia, atrial depolarization from a subsidiary pacemaker, intermittent sinus pauses, or a blunted heart rate response with exercise (chronotropic incompetence) 1.
- Atrioventricular Block: The clinical manifestations depend on whether the block is fixed or intermittent and the ventricular rate or duration of ventricular asystole associated with the block 1.
- Vagally Mediated Atrioventricular Block: This can occur at night during sleep when parasympathetic tone is increased and may be asymptomatic, or it can be associated with vasovagal syncope, leading to bradycardia 1.
- Other Causes: Brief episodes of bradycardia can also be triggered by medications, systemic illnesses, heart disease, and physical factors such as sleep apnea, which can lead to nocturnal bradyarrhythmias 1.
- Physiological Causes: In healthy individuals, especially young and conditioned athletes, brief episodes of bradycardia can occur during sleep due to vagal mediation and are usually asymptomatic 1.
It's crucial to consider the underlying cause and timing of bradycardia, as well as the presence of symptoms such as syncope, presyncope, dizziness, or heart failure symptoms, to determine the appropriate management strategy 1.
From the Research
Causes of Brief Episodes of Bradycardia
- Brief episodes of bradycardia can be caused by various factors, including:
- Sinus node dysfunction 2, 3, 4, 5
- Atrioventricular (AV) conduction disturbances 2, 3, 4, 5
- Intrinsic conditions causing damage to the conduction system 4
- Extrinsic conditions such as drugs (e.g., beta-blockers, glycosides, and/or calcium channel blockers) 4, 5
- Underlying treatable diseases 4
- Neurocardiogenic disorders (e.g., carotid sinus syndrome, vasovagal syncope) 6
- These conditions can lead to a range of symptoms, including syncope, dizziness, chest pain, dyspnea, or fatigue 2, 3, 4, 5, 6
Classification of Bradycardia
- Bradycardia can be classified into different types, including:
Diagnosis and Treatment
- Diagnosis of bradycardia is typically established through noninvasive diagnostic studies, such as 12-lead electrocardiogram, Holter electrocardiogram, exercise testing, event recorder, and implantable loop recorder 4
- Treatment for symptomatic bradycardia typically involves the implantation of a pacemaker 2, 3, 4, 5, 6
- The selection of an appropriate pacemaker system is crucial, with dual-chamber systems (DDD) preferred whenever possible to maintain AV synchrony 6