From the Guidelines
Brady arrhythmias are primarily caused by disruptions in the heart's electrical conduction system, often resulting from aging-related degenerative changes, medications, electrolyte imbalances, and structural heart diseases. The most common causes of brady arrhythmias include:
- Aging-related degenerative changes in the heart's conduction system
- Medications, particularly beta-blockers, calcium channel blockers, digoxin, and certain antiarrhythmics, as noted in the 2015 ESC guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death 1
- Electrolyte imbalances, especially potassium and calcium abnormalities
- Structural heart diseases like coronary artery disease, heart attacks, cardiomyopathies, and heart valve disorders
- Infections such as Lyme disease, endocarditis, and myocarditis
- Hypothyroidism, sleep apnea, and increased vagal tone
Treatment of brady arrhythmias depends on the underlying cause and severity of symptoms, ranging from medication adjustments to pacemaker implantation for persistent or symptomatic cases, as outlined in the 2012 ACCF/AHA/HRS focused update incorporated into the ACCF/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities 1. Patients experiencing dizziness, fainting, fatigue, or shortness of breath with a slow heart rate should seek medical attention promptly, as severe bradycardia can lead to inadequate blood flow to vital organs. The decision to implant a pacemaker for symptomatic bradycardia is often accompanied by uncertainty, and it is crucial to distinguish between physiological bradycardia due to autonomic conditions or training effects and circumstantially inappropriate bradycardia that requires permanent cardiac pacing, as discussed in the 2012 ACCF/AHA/HRS focused update 1. In cancer patients, bradycardia secondary to chemotherapy is often asymptomatic, but symptoms can include fatigue, dizziness, and pre-syncope/syncope, and treatment may involve pacemaker implantation or alternative therapy, as noted in the 2017 guidelines on cardiovascular complications of cancer therapy 1. In general, the management of brady arrhythmias should prioritize the patient's symptoms, underlying cause, and overall clinical status, with a focus on improving quality of life and reducing morbidity and mortality, as emphasized in the 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care 1.
From the Research
Causes of Bradyarrhythmias
- Bradyarrhythmias can be caused by disorders of impulse formation, such as diseases of the sinus node 2
- Conduction disturbances, including sinoatrial (SA), atrioventricular (AV) block, and bundle branch block, can also lead to bradyarrhythmias 2
- Pathology that produces bradycardia may occur within the sinus node, atrioventricular (AV) nodal tissue, and the specialized His-Purkinje conduction system 3
- Myocardial ischemia or infarction with necrosis of the cardiac pacemaker sites and/or conduction system can also cause bradyarrhythmias 4
- Other factors responsible for bradyarrhythmias include altered autonomic influence, systemic hypoxia, electrolyte disturbances, acid-based disorders, and complications of various medical therapies 4
Types of Bradyarrhythmias
- Sinus bradycardia: a heart rate lower than 60 beats/min 5
- Atrial bradycardia: a type of bradyarrhythmia that occurs in the atria 5
- Junctional bradycardia: a type of bradyarrhythmia that occurs in the atrioventricular junction 5
- Atrioventricular block: a type of conduction disturbance that can lead to bradyarrhythmias 5, 2