From the Guidelines
Complete heart block, also known as third-degree atrioventricular (AV) block, is primarily caused by age-related degenerative changes, ischemic heart disease, and congenital heart defects, as well as various medications, infectious diseases, and infiltrative diseases, which can disrupt the cardiac conduction system and lead to severe bradycardia. The causes of complete heart block can be categorized into several groups, including:
- Age-related degenerative changes in the cardiac conduction system, such as fibrosis and sclerosis of the conduction pathways, which accounts for approximately 50% of cases 1
- Ischemic heart disease, particularly myocardial infarction affecting the AV node blood supply, is another significant cause
- Various medications can induce complete heart block, including beta-blockers, calcium channel blockers, digoxin, and certain antiarrhythmics like amiodarone
- Infectious diseases such as Lyme disease, endocarditis, myocarditis, and Chagas disease can damage the conduction system
- Congenital heart defects may present with complete heart block at birth or later in life, as noted in the guidelines for cardiac pacing and cardiac resynchronization therapy 1
- Infiltrative diseases (amyloidosis, sarcoidosis), autoimmune conditions (systemic lupus erythematosus, rheumatoid arthritis), and electrolyte disturbances (severe hyperkalemia) can also disrupt AV conduction
- Trauma to the heart, either from blunt force injury or as a complication of cardiac surgery, may damage the conduction system, and the decision for permanent pacing is at the physician’s discretion 1
Understanding these causes is essential for proper diagnosis and management, which often requires pacemaker implantation to prevent the potentially fatal consequences of severe bradycardia. The decision regarding implantation of a pacemaker must be considered with respect to whether AV block will be permanent, and reversible causes of AV block, such as electrolyte abnormalities, should be corrected first 1.
From the Research
Causes of Complete Heart Block
The causes of complete heart block (Third-degree atrioventricular block) can be categorized into several factors, including:
- Congenital complete heart block, which may occur in isolation or as a consequence of anomalous development of the conduction tissue in the context of a cardiac malformation 2
- Acquired complete heart block, which can be caused by various factors such as:
- Myocardial bridging, where cardiac tissue compresses a coronary artery during systole 3
- Hypertensive cardiomyopathy due to ongoing uncontrolled hypertension, which can be caused by bilateral renal artery stenosis 4
- Immune-mediated injury of the conduction system, which occurs as a result of transplacental passage of maternal anti-SSA/Ro-SSB/La antibodies 2
- Other potential causes, including infections, cardiac ischemia or myopathies, autoimmune diseases, or endocrinological diseases, which should be excluded through extensive work-up 4
- Systemic lupus erythematosus, both clinically manifested and subclinical, with positive antibodies (SS-A and SS-B antibodies), which can increase the risk of congenital complete heart block in infants 5