It produces the signal that starts each heartbeat.īradycardia occurs when these signals slow down or are blocked.
The sinus node is the heart's natural pacemaker. Within the upper right chamber of the heart (right atrium) is a group of cells called the sinus node. The typical heart has four chambers - two upper chambers (atria) and two lower chambers (ventricles). To better understand the causes of bradycardia, it may be helpful to know how the heart typically beats. Certain medications, including sedatives, opioids, and drugs used to treat heart rhythm disorders, high blood pressure and certain mental health disorders.Inflammatory disease, such as rheumatic fever or lupus.Repeated pauses in breathing during sleep (obstructive sleep apnea).Imbalance of chemicals in the blood, such as potassium or calcium.An underactive thyroid gland (hypothyroidism).Inflammation of heart tissue (myocarditis).A heart condition present at birth (congenital heart defect).
The signal then travels through the atria to the atrioventricular (AV) node and into the ventricles, causing them to contract and pump blood. In a typical heart rhythm, a tiny cluster of cells at the sinus node sends out an electrical signal.
