Junctional rhythm
Encyclopedia
Junctional rhythm describes an abnormal heart rhythm
resulting from impulses coming from a locus of tissue in the area of the atrioventricular node
, the "junction" between atria and ventricles.
Under normal conditions, the heart's sinoatrial node
determines the rate by which the organ beats - in other words, it is the heart's "pacemaker." The electrical activity of sinus rhythm
originates in the sinoatrial node and depolarizes the atria. Current then passes from the atria through the bundle of His
, from which it travels along Purkinje fibers
to reach and depolarize the ventricles. This sinus rhythm is important because it ensures that the heart's atria reliably contract before the ventricles.
In junctional rhythm, however, the sinoatrial node does not control the heart's rhythm - this can happen in the case of a block in conduction somewhere along the pathway described above. When this happens, the heart's atrioventricular node
takes over as the pacemaker.. In the case of a junctional rhythm, the atria will actually still contract before the ventricles; however, this does not happen by the normal pathway and instead is due to retrograde conduction (conduction comes from the ventricles or from the AV node into and through the atria)..
Junctional rhythm can be diagnosed by looking at an ECG: it usually presents without a P wave or with an inverted P wave. Occasionally the P wave will be retrograde, meaning appearing after the QRS complex.
Heart Rhythm
Heart Rhythm is a peer-reviewed medical journal that covers the study and management of cardiac arrhythmia. It is the official journal of the Heart Rhythm Society and the Cardiac Electrophysiology Society...
resulting from impulses coming from a locus of tissue in the area of the atrioventricular node
Atrioventricular node
The atrioventricular node is a part of the electrical control system of the heart that coordinates heart rate. It electrically connects atrial and ventricular chambers...
, the "junction" between atria and ventricles.
Under normal conditions, the heart's sinoatrial node
Sinoatrial node
The sinoatrial node is the impulse-generating tissue located in the right atrium of the heart, and thus the generator of normal sinus rhythm. It is a group of cells positioned on the wall of the right atrium, near the entrance of the superior vena cava...
determines the rate by which the organ beats - in other words, it is the heart's "pacemaker." The electrical activity of sinus rhythm
Sinus rhythm
In medicine, sinus rhythm is the normal beating of the heart, as measured by an electrocardiogram . It has certain generic features that serve as hallmarks for comparison with normal ECGs.- ECG structure :...
originates in the sinoatrial node and depolarizes the atria. Current then passes from the atria through the bundle of His
Bundle of His
The bundle of His, known as the AV bundle or atrioventricular bundle, is a collection of heart muscle cells specialized for electrical conduction that transmits the electrical impulses from the AV node to the point of the apex of the fascicular branches...
, from which it travels along Purkinje fibers
Purkinje fibers
For the nervous cells, see Purkinje cellPurkinje fibers are located in the inner ventricular walls of the heart, just beneath the endocardium...
to reach and depolarize the ventricles. This sinus rhythm is important because it ensures that the heart's atria reliably contract before the ventricles.
In junctional rhythm, however, the sinoatrial node does not control the heart's rhythm - this can happen in the case of a block in conduction somewhere along the pathway described above. When this happens, the heart's atrioventricular node
Atrioventricular node
The atrioventricular node is a part of the electrical control system of the heart that coordinates heart rate. It electrically connects atrial and ventricular chambers...
takes over as the pacemaker.. In the case of a junctional rhythm, the atria will actually still contract before the ventricles; however, this does not happen by the normal pathway and instead is due to retrograde conduction (conduction comes from the ventricles or from the AV node into and through the atria)..
Junctional rhythm can be diagnosed by looking at an ECG: it usually presents without a P wave or with an inverted P wave. Occasionally the P wave will be retrograde, meaning appearing after the QRS complex.