Junctional Bradycardia

Junctional Bradycardia is a condition affecting the heart. Bradycardia is a general term describing any number of physiological or pathological conditions that cause a slowed heart beat. A typical adult heart beat is around 60-100 beats per minute. A resting heart beat under 60 beats per minute is define as bradycardic. However, symptoms do not generally present until under 50 beats per minute.

There are two bundles of autorhythmic pacemaker cells within the heart. These are the sinoatrial node situated in the upper portion of the right atrium and the atrioventricular node, situated in the junction between the atria and ventricles of the heart. These nodes create the electrical impulses that cause the atria then the ventricles to contract and the heart to beat. The sinoatrial node is the heart’s primary pacemaker. The autorhythmic (self governing) sinoatrial node (SA node) maintains the heart rate at 60-100 beats per minute. Typically electrical impulses are conducted from the sinoatrial nodes then to the atrioventriular node (AV node).

If the sinoatrial node fails to fire, the second pacemaker in the heart, the atrioventricular node will remain to pace the heart’s contrations. The atriventricular node autorhythmically maintains a contraction rate of 40-60 beats per minute. Therefore, junctional bradycardia refers to a slowed pulse (heart rate) that is generated from the AV node due to SA node failure.

Martini, Fredric, H. 2006. Fundamentals of anatomy and physiology. 7th ed. Pearson Education Inc. USA.