Junctional Rhythms / A-V
Nodal Rhythm
Aims and Objectives.
 Investigate common types of Junctional and
AV nodal tachycardias.
 Understand underlying mechanisms.
 Common presentations and ECG
 Difficulties in interpretation.
Junctional rhythm occurs due to SA node
A-V Node acts as pacemaker.
 Conduction begins in AV node.
1. Normal conduction through ventricles.
2. Retrograde conduction through the atria.
Rate :- 40-60 bpm
ECG Criteria
 Inverted P wave observed on ECG.
 The P-Wave in V1 becomes pointed and positive (normally
 The speed of the retrograde conduction will affect the
position of the P-Wave relative to the QRS complex on the
 The speed of the retrograde conduction & position of P
wave depends on the area of the AV node that initiates
 Which ever portion of the AV node is acting as the
pacemaker will determine the speed and order of
conduction through Atria/Ventricles.
High AV Nodal Rhythm
 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.
P wave sinus
P wave nodal
High AV Nodal Rhythm
Mid AV nodal Rhythm
 The Mid portion of the AV node takes over the pacemaker
function of the heart.
 Causing the Atria and the Ventricles to be depolarised
 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)
P wave nodal
P wave nodal
Mid AV Nodal Rhythm
Low AV nodal rhythm
 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
P wave nodal
P wave nodal
Low AV Nodal Tachycardia.
AV Re-Entrant Tachycardia
 Accessory pathway
from atria to ventricle.
 Usually includes AV
node + another
abnormal pathway.
 Abnormal accessory
pathway from atria to
ventricle – e.g. Bundle
of Kent in WPW.
AV Re-entrant Tachycardia
 Abnormal circuit from atria to ventricle.
 Via abnormal accessory pathway.
 Two common pathophysiological processes:
– Orthodromic AVRT.
– Antidromic AVRT.
Orthodromic AVRT.
Orthodromic AVRT.
 Impulses down AV node then conducted retrogradely
via accessory pathway to atria.
 Results in p waves preceding QRS – retrograde atrial
Antidromic AVRT
 Impulses conducted down AV – abnormal accessory
pathway first.
 Then up through AV node itself retrogradely.
 Often results in broad complex with visible ‘delta wave’.
Antidromic AVRT
Wolf-Parkinson White
 Accessory Pathway connecting the atria to
the ventricles.
 Very rare cause of sudden death.
 1-2 people in every 1000.
 Re-entrant circuit.
 < 0.1 % of people die of VF.
WPW Syndrome.
WPW cont….
 Causes.
1. Unknown, not hereditary.
2. Impossible to prevent.
1. Palpitations :- Breath hold.
 Treatment.
1. RF Ablation.
2. Medical Therapy.
Atrio-Ventricular Nodal Tachycardia
AV Nodal Pathway
 Circus movement within the AV node.
 Two pathways exist within the AV node –
slow and fast.
 Typically during tachycardia signals travel
down the slow and up the fast
 Atypically the reverse may happen, down
the fast and up the slow.
 Most common SVT.
 Symptoms:- Palpitations
 Treatment:- Medical therapy
Carotid sinus Massage
RF Ablation
AVNRT Example
 Numerous different variations of AV nodal
and junctional tachycardias.
 Can be difficult to distinguish via ECG
appearance alone.
 Important to recognise ‘abnormal
 Often grouped under SVT – further
eloctrophysiological study often required.

Junctional Rhythms / A-V Nodal Rhythm