A junctional escape beat is a delayed
heartbeat
A heartbeat is one cardiac cycle of the heart.
Heartbeat, heart beat, heartbeats, and heart beats may refer to:
Computing
*Heartbeat (computing), a periodic signal to indicate normal operation or to synchronize parts of a system
*Heartbeat, clus ...
originating not from the
atrium but from an
ectopic focus somewhere in the
atrioventricular junction. It occurs when the rate of depolarization of the
sinoatrial node
The sinoatrial node (also known as the sinuatrial node, SA node or sinus node) is an oval shaped region of special cardiac muscle in the upper back wall of the right atrium made up of cells known as pacemaker cells. The sinus node is approxi ...
falls below the rate of the
atrioventricular node
The atrioventricular node or AV 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 lower back section of t ...
. 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 or blocked
premature atrial contraction
Premature atrial contraction (PAC), also known as atrial premature complexes (APC) or atrial premature beats (APB), are a common cardiac dysrhythmia characterized by premature heartbeats originating in the atria. While the sinoatrial node typic ...
.
Signs and symptoms
Junctional rhythms (if a
bradycardia
Bradycardia (also sinus bradycardia) is a slow resting heart rate, commonly under 60 beats per minute (BPM) as determined by an electrocardiogram. It is considered to be a normal heart rate during sleep, in young and healthy or elderly adults, ...
) 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: th ...
. 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 feel ...
,
dizziness
Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-specific feeling, such as giddiness or foolishness.
Dizziness is a common medical ...
,
low blood pressure
Hypotension is low blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood. Blood pressure is indicated by two numbers, the systolic blood pressure (the top number) and the dia ...
, 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.
See also
*
Ectopic beat
*
Junctional rhythm
References
External links
{{DEFAULTSORT:Junctional Escape Beat
Cardiac arrhythmia