| Adaptive |
Highly trained athletes and individuals with increased vagal tone. |
| Respiratory |
Hypoxia; apnea/bradycardia of prematurity. |
| Cardiac |
Sinus node dysfunction (hereditary or secondary); CHD; atrial septal defect; after cardiac surgery/transcatheter repair. |
| Genetics |
Progressive hereditary cardiac conduction disorders: SCN5A, TBX5, SCN1B-LOF, CASQ2, HCN4, etc. |
| Neurocardiogenic |
Increased vagal tone; Bezold-Jarisch reflex; situational (cough, breath-holding attacks, sleep, etc.); esophageal, nasopharyngeal, peritoneal, or rectal stimulation. |
| Neurological |
Increased intracranial pressure; Chiari malformation. |
| Psychiatric |
Anorexia nervosa. |
| Endocrine |
Hypothyroidism. |
| Pharmacological |
Beta-blockers; alpha-2 agonists; fentanyl; phenylephrine; methoxamine. |
| Miscellaneous |
Hypothermia. Hypoglycemia. Electrolyte abnormalities: hypo/hyperkalemia; hypo/hypercalcemia; hypomagnesemia. |
|
Third-degree AV block / Complete heart block
|
|
Origin
|
Causes
|
| Cardiac |
Congenital; CHD; genetic disorders; long QT syndrome; transposition of the great arteries; cardiac surgery; coronary artery disease. |
| Immune |
Maternal connective tissue disease; systemic lupus erythematosus; Sjögren's syndrome. |
| Infectious |
Myocarditis; endocarditis; Lyme disease; Chagas disease; diphtheria; rubella; mumps; trichinosis; Rocky Mountain spotted fever; HIV/AIDS; acute rheumatic fever. |
| Metabolic |
Kearns-Sayre syndrome; carnitine deficiency; glycogen storage diseases. |
| Miscellaneous |
Muscular dystrophy; eosinophilic cardiomyopathy; idiopathic. |
