Junctional Rhythms / A-V Junctional Rhythms / A-V Nodal RhythmNodal Rhythm

Aims and Objectives.Aims and Objectives.

Investigate common types of Junctional and Investigate common types of Junctional and AV nodal tachycardias.AV nodal tachycardias.

Understand underlying mechanisms.Understand underlying mechanisms. Common presentations and ECG Common presentations and ECG

appearances.appearances. Difficulties in interpretation.Difficulties in interpretation.

Junctional rhythm occurs due to SA node Junctional rhythm occurs due to SA node disease.disease.

A-V Node acts as pacemaker.A-V Node acts as pacemaker.

Conduction begins in AV node.Conduction begins in AV node.1.1. Normal conduction through ventricles.Normal conduction through ventricles.2.2. Retrograde conduction through the atria.Retrograde conduction through the atria.

Rate :- 40-60 bpmRate :- 40-60 bpm

ECG CriteriaECG Criteria Inverted P wave observed on ECG.Inverted P wave observed on ECG.

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

The speed of the retrograde conduction will affect The speed of the retrograde conduction will affect the position of the P-Wave relative to the QRS the position of the P-Wave relative to the QRS complex on the ECG.complex on the ECG.

The speed of the retrograde conduction & position The speed of the retrograde conduction & position of P wave depends on the area of the AV node that of P wave depends on the area of the AV node that initiates impulse.initiates impulse.

Which ever portion of the AV node is acting as the Which ever portion of the AV node is acting as the pacemaker will determine the speed and order of pacemaker will determine the speed and order of conduction through Atria/Ventriclesconduction through Atria/Ventricles..

HIGH

MID

LOW

High AV Nodal RhythmHigh AV Nodal Rhythm The head of the AV node, nearest to the Atrial The head of the AV node, nearest to the Atrial

myocardium takes over the pacemaker function of myocardium takes over the pacemaker function of the heart.the heart.

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

P wave sinus P wave nodal

High AV Nodal RhythmHigh AV Nodal Rhythm

Mid AV nodal RhythmMid AV nodal Rhythm The Mid portion of the AV node takes over the The Mid portion of the AV node takes over the

pacemaker function of the heart.pacemaker function of the heart. Causing the Atria and the Ventricles to be depolarised Causing the Atria and the Ventricles to be depolarised

simultaneously.simultaneously. Results in the inverted P-Wave being seen within the Results in the inverted P-Wave being seen within the

QRS complex therefore altering the appearance of the QRS complex therefore altering the appearance of the QRS complex. (NB there is no preceding P-Wave)QRS complex. (NB there is no preceding P-Wave)

P wave nodal P wave nodal

Mid AV Nodal RhythmMid AV Nodal Rhythm

Low AV nodal rhythmLow AV nodal rhythm The lowest portion of the AV node takes over the The lowest portion of the AV node takes over the

pacemaker function of the heart. pacemaker function of the heart. Causes the ventricles to be depolarise before the atria Causes the ventricles to be depolarise before the atria

are depolarised retrogradely. are depolarised retrogradely. Results in the inverted P-Wave being seen after each Results in the inverted P-Wave being seen after each

QRS complex.QRS complex.

P wave nodal P wave nodal

Low AV Nodal Tachycardia.Low AV Nodal Tachycardia.

AV Re-Entrant TachycardiaAV Re-Entrant Tachycardia

Accessory pathway Accessory pathway from atria to ventricle.from atria to ventricle.

Usually includes AV Usually includes AV node + another node + another abnormal pathway.abnormal pathway.

Abnormal accessory Abnormal accessory pathway from atria to pathway from atria to ventricle – e.g. Bundle ventricle – e.g. Bundle of Kent in WPW.of Kent in WPW.

AV Re-entrant TachycardiaAV Re-entrant Tachycardia

Abnormal circuit from atria to ventricle.Abnormal circuit from atria to ventricle. Via abnormal accessory pathway.Via abnormal accessory pathway. Two common pathophysiological processes:Two common pathophysiological processes:

– Orthodromic AVRT.Orthodromic AVRT.– Antidromic AVRT.Antidromic AVRT.

Orthodromic AVRT.Orthodromic AVRT.

Orthodromic AVRT.Orthodromic AVRT.

Impulses down AV node then conducted retrogradely Impulses down AV node then conducted retrogradely via accessory pathway to atria.via accessory pathway to atria.

Results in p waves preceding QRS – retrograde atrial Results in p waves preceding QRS – retrograde atrial conduction.conduction.

Antidromic AVRTAntidromic AVRT

Impulses conducted down AV – abnormal accessory Impulses conducted down AV – abnormal accessory pathway first.pathway first.

Then up through AV node itself retrogradely.Then up through AV node itself retrogradely. Often results in broad complex with visible ‘delta wave’.Often results in broad complex with visible ‘delta wave’.

Antidromic AVRTAntidromic AVRT

Wolf-Parkinson WhiteWolf-Parkinson White Accessory Pathway connecting the atria to Accessory Pathway connecting the atria to

the ventricles.the ventricles.

Very rare cause of sudden death.Very rare cause of sudden death.

1-2 people in every 1000.1-2 people in every 1000.

Re-entrant circuit.Re-entrant circuit.

< 0.1 % of people die of VF.< 0.1 % of people die of VF.

WPW Syndrome.WPW Syndrome.

WPW cont….WPW cont….

Causes.Causes.1.1. Unknown, not hereditary.Unknown, not hereditary.2.2. Impossible to prevent.Impossible to prevent.

Symptoms.Symptoms.1.1. Palpitations :- Breath hold.Palpitations :- Breath hold.

Treatment.Treatment.1.1. RF Ablation.RF Ablation.2.2. Medical Therapy.Medical Therapy.

Atrio-Ventricular Nodal TachycardiaAtrio-Ventricular Nodal Tachycardia

AV Nodal PathwayAV Nodal Pathway Circus movement within the AV node.Circus movement within the AV node.

Two pathways exist within the AV node – Two pathways exist within the AV node – slow and fast.slow and fast.

Typically during tachycardia signals travel Typically during tachycardia signals travel down the slow and up the fastdown the slow and up the fast

Atypically the reverse may happen, down Atypically the reverse may happen, down the fast and up the slow.the fast and up the slow.

AVNRTAVNRT Most common SVT.Most common SVT.

Symptoms:- PalpitationsSymptoms:- Palpitations

SyncopeSyncope

Treatment:- Medical therapyTreatment:- Medical therapy

Carotid sinus Massage Carotid sinus Massage

RF AblationRF Ablation

AVNRT ExampleAVNRT Example

AVNRTAVNRT

Conclusion.Conclusion.

Numerous different variations of AV nodal Numerous different variations of AV nodal and junctional tachycardias.and junctional tachycardias.

Can be difficult to distinguish via ECG Can be difficult to distinguish via ECG appearance alone.appearance alone.

Important to recognise ‘abnormal Important to recognise ‘abnormal tachycardia’.tachycardia’.

Often grouped under SVT – further Often grouped under SVT – further eloctrophysiological study often required.eloctrophysiological study often required.