Low heart rate, or bradycardia, can be caused by a variety of factors related to the heart's electrical system, metabolic issues, medications, and other health conditions. Key causes include:
- Problems with the sinoatrial (SA) node, the heart's natural pacemaker, or disruptions in the heart's electrical conduction pathways that slow the transmission of impulses from the atria to the ventricles
- Age-related degenerative changes in the heart's conduction system, making bradycardia more common in older adults
- Heart damage from conditions such as heart attack, heart disease, myocarditis (heart infection), or complications from heart surgery
- Metabolic and chemical imbalances, including low thyroid hormone levels (hypothyroidism) and abnormal blood levels of minerals like potassium, calcium, and magnesium
- Certain medications, such as beta blockers, calcium channel blockers, sedatives, opioids, antiarrhythmics, and some used for mental health or chemotherapy, which can slow the heart rate as a side effect
- Sleep disorders like obstructive sleep apnea, which cause repeated breathing interruptions that affect heart rhythm
- Inflammatory and autoimmune diseases such as lupus, rheumatic fever, rheumatoid arthritis, sarcoidosis, and infections like Lyme disease or Chagas disease that can damage the heart's electrical pathways
- Athletic conditioning, where a strong and efficient heart beats more slowly at rest, is a normal cause of low heart rate in physically active individuals and athletes
In summary, low heart rate can result from electrical system dysfunction, metabolic imbalances, medication effects, heart damage, sleep apnea, inflammation, or healthy adaptation in athletes
