Junctional Rhythms/ AV nodal rhythms

Question 1

What are junctional rhythms

Answer 1

The AVN has intrinsic automaticity that allows it to initiate and depolarise the myocardium during significant sinus bradycardia or complete heart block.

Diseased SA node leads to the AV node/His Bundle taking over due to higher automaticity of the ectopic pacemaker.

Conduction begins in the AVN.
Normal conduction through ventricles.
Retrograde conduction through the atria.

Rate : 40-60 bpm

Question 2

ECG criteria junctional rhythms

Answer 2

Inverted P wave on ECG.

The P wave in V1 becomes pointed and positive (normally biphasic).

The position of the P wave depends on the area of the AV node that initiates impulse.

Whichever portion of the AV node is acting as the pacemaker will determine the speed and order of conduction through atria/ventricles.

Question 3

Where is the AV node located?

Answer 3

Interatrial septum, near opening of coronary sinus, above Tvalve

Question 4

High AV Nodal Rhythm

Answer 4

The head of the AV node, nearest to the Atrial myocardium takes over the pacemaker function of the heart.

Results in an inverted P-Wave preceding the QRS complex and a shortened PR Interval.

Question 5

Mid AV nodal Rhythm

Answer 5

The mid portion of the AV node takes over the pacemaker function of the heart.
Causing the atria and the ventricles to be depolarised simultaneously.
Results in the inverted P-Wave being seen within the QRS complex therefore altering the appearance of the QRS complex. (NB there is no preceding P-Wave).

Question 6

Low AV nodal rhythm

Answer 6

The lowest portion of the AV node takes over the pacemaker function of the heart.
Causes the ventricles to be depolarise before the atria are depolarised retrogradely.
Results in the inverted P-Wave being seen after each QRS complex.

Question 7

Accelerated junctional rhythm

Answer 7

A junctional rhythm with a rate of 60-100 bpm.

Can occur after acute MI or due to hyperkalaemia, digitalis toxicity and thyrotoxicosis .

May lead to haemodynamic instability due to loss of synchronised atrial contraction.

Question 8

Treatment of junctional rhythm

Answer 8

Depends on underlying cause.

Healthy, asymptomatic – no medical management required.

Permanent pacemaker for those with SND or high grade AVB.

If caused by digoxin toxicity or treatment with CCB/ beta blockers/ ivabradine/ anti-arrhythmics, the medication should be reduced/stopped.