A junctional escape beat is a delayed heartbeat originating not from the atrium but from an ectopic focus somewhere in the

atrioventricular junction 350px, Image showing the cardiac pacemaker or SA node, the primary pacemaker within the electrical conduction system of the heart The cardiac pacemaker is the heart's natural rhythm generator. It employs pacemaker Cell (biology), cells that ...

. It occurs when the rate of depolarization of the

sinoatrial node The sinoatrial node (also known as the sinuatrial node, SA node, sinus node or Keith–Flack node) is an ellipse, oval shaped region of special cardiac muscle in the upper back wall of the right atrium made up of Cell (biology), cells known as pa ...

falls below the rate of the

atrioventricular node The atrioventricular node (AV node, or Aschoff-Tawara node) electrically connects the heart's atria and ventricles to coordinate beating in the top of the heart; it is part of the electrical conduction system of the heart. The AV node lies at the ...

. This dysrhythmia also may occur when the electrical impulses from the SA node fail to reach the AV node because of SA or AV block. It is a protective mechanism for the heart, to compensate for the SA node no longer handling the pacemaking activity, and is one of a series of backup sites that can take over pacemaker function when the SA node fails to do so. It can also occur following a

premature ventricular contraction A premature ventricular contraction (PVC) is a common event where the heartbeat is initiated by Purkinje fibers in the ventricles rather than by the sinoatrial node. PVCs may cause no symptoms or may be perceived as a "skipped beat" or felt as ...

or blocked

premature atrial contraction Premature atrial contraction (PAC), also known as atrial premature complexes (APC) or atrial premature beats (APB), are a common arrhythmia characterized by premature heartbeats originating in the atria. While the sinoatrial node typically re ...

Signs and symptoms

Junctional rhythm Junctional rhythm also called nodal rhythm describes an abnormal heart rhythm resulting from impulses coming from a locus of tissue in the area of the atrioventricular node (AV node), the "junction" between atria and ventricles. Under normal cond ...

s (if a

bradycardia Bradycardia, also called bradyarrhythmia, is a resting heart rate under 60 beats per minute (BPM). While bradycardia can result from various pathological processes, it is commonly a physiological response to cardiovascular conditioning or due ...

) can cause decreased

cardiac output In cardiac physiology, cardiac output (CO), also known as heart output and often denoted by the symbols Q, \dot Q, or \dot Q_ , edited by Catherine E. Williamson, Phillip Bennett is the volumetric flow rate of the heart's pumping output: tha ...

. Therefore, the person may exhibit signs and symptoms similar to other bradycardia such as

lightheadedness Lightheadedness is a common and typically unpleasant sensation of dizziness or a feeling that one may faint. The sensation of lightheadedness can be short-lived, prolonged, or, rarely, recurring. In addition to dizziness, the individual may fee ...

dizziness Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to Balance disorder, disequilibrium or a non-specific feeling, such as giddiness or foolishness. Dizziness is a ...

low blood pressure Hypotension, also known as low blood pressure, is a cardiovascular condition characterized by abnormally reduced blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood and is ...

, and

fainting Syncope , commonly known as fainting or passing out, is a loss of consciousness and muscle strength characterized by a fast onset, short duration, and spontaneous recovery. It is caused by a decrease in blood flow to the brain, typically from ...

. This rhythm can usually be tolerated if the rate is above 50 beats per minute.

Cause

A junctional escape complex is a normal response that may result from excessive vagal tone on the SA node (e.g. digoxin toxicity), a pathological slowing of the SA discharge, or a complete AV block.

Diagnosis

* Rate: 35–60 bpm * Rhythm: Irregular in single junctional escape complex; regular in junctional escape rhythm. * P waves: Depends on the site of the ectopic focus. They will be inverted, and may appear before or after the QRS complex, or they may be absent, hidden by the QRS. * P-R interval: If the P wave occurs before the QRS complex, the interval will be less than 0.12 seconds. * QRS Complex: Usually normal in duration and morphology, less than 0.12 seconds.

References

External links

{{DEFAULTSORT:Junctional Escape Beat Cardiac arrhythmia

Signs and symptoms

Cause

Diagnosis

See also

References

External links