1. Junctional Rhythms / A-V Nodal Rhythm

2. Aims and Objectives.  Investigate common types of Junctional and AV nodal tachycardias.  Understand underlying mechanisms.  Common presentations and ECG appearances.  Difficulties in interpretation.

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

4. ECG Criteria  Inverted P wave observed on ECG.  The P-Wave in V1 becomes pointed and positive (normally biphasic).  The speed of the retrograde conduction will affect the position of the P-Wave relative to the QRS complex on the ECG.  The speed of the retrograde conduction & position of P wave depends on the area of the AV node that initiates impulse.  Which ever portion of the AV node is acting as the pacemaker will determine the speed and order of conduction through Atria/Ventricles.

5. HIGH MID LOW

6. 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

7. High AV Nodal Rhythm

8. 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 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) P wave nodal

9. Mid AV Nodal Rhythm

10. 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 complex. P wave nodal

11. Low AV Nodal Tachycardia.

12. 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.

13. AV Re-entrant Tachycardia  Abnormal circuit from atria to ventricle.  Via abnormal accessory pathway.  Two common pathophysiological processes: –Orthodromic AVRT. –Antidromic AVRT.

14. Orthodromic AVRT.

15.  Impulses down AV node then conducted retrogradely via accessory pathway to atria.  Results in p waves preceding QRS – retrograde atrial conduction.

16. 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’.

17. Antidromic AVRT

18. 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.

20. WPW Syndrome.

21. WPW cont….

22.  Causes. 1.Unknown, not hereditary. 2.Impossible to prevent. Symptoms. 1.Palpitations :- Breath hold.  Treatment. 1.RF Ablation. 2.Medical Therapy.

23. Atrio-Ventricular Nodal Tachycardia

24. 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.

25. AVNRT  Most common SVT.  Symptoms:- Palpitations Syncope Syncope  Treatment:- Medical therapy Carotid sinus Massage Carotid sinus Massage RF Ablation RF Ablation

26. AVNRT Example

27. AVNRT

28. Conclusion.  Numerous different variations of AV nodal and junctional tachycardias.  Can be difficult to distinguish via ECG appearance alone.  Important to recognise ‘abnormal tachycardia’.  Often grouped under SVT – further eloctrophysiological study often required.