Bradycardia Etiology and Management in Adults

Primary Classification of Causes

The American College of Cardiology states that degenerative fibrosis of the conduction system is the most common intrinsic cause in elderly patients, typically affecting those in their 70s and 80s, and can manifest as sinus node dysfunction, atrioventricular conduction disease, or tachy-brady syndrome 1, 2
Ischemic heart disease and myocardial infarction represent critical cardiac causes, particularly inferior MI affecting the AV node blood supply, with associated cardiac conditions including heart failure, valvular heart disease, and atrial fibrillation 1, 2

The European Heart Journal notes that multiple pathophysiologic processes can compromise impulse initiation and propagation, with medications being the most common reversible cause, including beta-blockers, calcium channel blockers, digoxin, antiarrhythmic drugs, and ivabradine 1, 2, 3
Metabolic and endocrine disorders, such as hypothyroidism, electrolyte abnormalities, and hypoxemia, are common and immediately reversible causes of bradycardia 2, 3, 4
Acute cardiac events, including acute myocardial infarction and myocarditis, can cause bradycardia, with acute myocardial infarction accounting for 14% of emergency bradycardia presentations 3, 4

The American College of Cardiology recommends that the key clinical question is not the absolute heart rate, but whether bradycardia correlates with symptoms, and that failing to identify reversible causes before considering permanent pacing is a critical error 1, 2
The European Heart Journal notes that in emergency settings, 45% of compromising bradycardia cases had reversible etiologies, including drugs, myocardial infarction, intoxication, and electrolyte abnormalities 3