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 appearances. Difficulties in interpretation. 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 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. HIGH MID LOW 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 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 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 complex. 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 conduction. 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. Symptoms. 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. AVNRT Most common SVT. Symptoms:- Palpitations Syncope Treatment:- Medical therapy Carotid sinus Massage RF Ablation AVNRT Example AVNRT 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.