When Not To Use Term "Junctional Rhythm"

I always gets fascinated by the Use of this term accelerated junctional rhythm . I know it’s a very very favourite term of many of the Drs may be because it’s easy to use , easy to remember , but unfortunately not many times its use is not appropriate as per situation.

To understand junctional or rhythms originating from junction one needs to understand the anatomy & physiology of the area which is called junction !!!!!! 

And this will also help in understanding of terms like junction , junctional escape , accelerated junctional !!!  

Generally The terms AV junctional, junctional, AV nodal, and nodal are, however, all essentially synonymous.

Tawara(early 19th century) was the to published about AVN and AVJ & and So The thought that the AVJ having a pacemaking function is not at all new! 

Definition of AVJ ! Are areas where the atrial myocardium inserts into, and is separated from, the base of the ventricular mass, apart from at the site of penetration of the specialised axis for atrioventricular conduction.

it has been demonstrated that the AV junctional pacemaker rhythm originates from the NH region or His bundle in studies esp in the failing human heart.

And this area is electrically isolated from the ventricular muscle !!!

The two main types of rhythm

Originating from AVJ are 

1. Junctional escape rhythum 

2. Accelerated junctional rhythm 

A. Junctional escape rhythum 

An Escape rhythum is defined as at least three escape impulses in a row. The R to R of the junctional escape complexes is usually constant and varies less than 0.04 second, although exceptions do occur.

The AVJ may also become the site of impulse formation when the VR becomes slower than the inherent rate of the junctional pacemaker (35 to 60 beats/min) !!!!

Such an AVJR is an escape phenomenon and represents the slow or passive type of junctional rhythm!!!! This is caused by an abnormal increase in the automaticity of the junctional pacemaker ! 

Clinically, this is also commonly observed during periods of Sinus arrests , so then it fulfils the role of an escape pacemaker.                                             

Surface ecg presentation 

The QRS of AV junctional origin is similar to that originating from sinus or any supraventricular focus. 

It is usually narrow like sinus but its morphology may differ slightly from that of any sinus complex. This may also become wide if there is a preexisting intraventricular conduction delay. 

    

B. Accelerated AV JR 

Accelerated AVJR also now called as non-paroxysmal AV junctional tachy or NPJT.     

This is also like a form of an SVT however this is caused by enhanced impulse formation within the AVJ rather than by reentry as like in AVNRT .                                  

1. Mechanism of causation !!!!!!automatic with the following few characteristics: A. moderately increased, JR , about 70 to 130 beats/min. B. lacks sudden onset and offset that are characteristic of the Psvt (AVNRT).                  

16. Causes !!! Are usually due to A. recent cardiac surgery like aortic or MV surgery( most commonest cause nowdays)

        C. Acute MI (10% of MI , more common with inf MI than ant but poor prognosis with Ant MI) 

         D. Dig toxicity 

         E. myocarditis 

         F. Periods of sympathetic overdrive 

          G. Only in rare instances does the cause of the arrhythmia remain unexplained. 

( Treatment of this rhythm will be directed toward correction of the underlying disorder) 

Surface ecg presentations in JR ? 

A. In case of presence of retrograde conduction capability ! 

constant relation will exist bw A & V . 

The P will be inverted in inf leads & usually isoelectric or upright in leads aVR and I & variable morphology In the precordial leads . 

The P may precede, be superimposed on, or follow the QRS. If preceding the QRS the PR interval will be less than 0.11 second , & if after the QRS the RP interval varies and but may be as long as 0.20 sec or even longer.

B. If no retrograde condition capacity exists in that particular individual then the atria remain under control of the sinus resulting in A to V dissociation .

Hope this description helped you in understanding Junctional Rhythm 😊