AV dissociation.pptx

Av block

1. AV dissociation By d.anishaa

2. AV DISSOCIATION- independent/ dissociated activity of atria and vetricles . Not a primary disturbance of rhythm rather is a symptom of underlying rhythm disturbances produced by one of three mechanism /combination which impairs normal transmission of impulse from atria to ventricles.

3. LOCATION : AV junction- CHB INTERFERENCE FROM ACCELARATED LOWER PACEMAKER –VT/ AIVR

4. CLASSIFICATION Type 1: AV Dissociation by Default Slowing of dominant pacemaker– allows escape of subsidiary pacemaker May occur in sinus bradycardia /sinus arrhythmia – permit independent AV junctional rhythm to arise

5. Sinus bradycardia High vagal tone beta-adrenergic blockers and calcium channel blockers

6. Type II: ACCELARATION OF LATENT PACEMAKER : Non paroxysmal AV junctional tachycardia VT without retrograde atrial capture insults lead to an accelerated rate of the subsidiary pacemakers, causing them to conduct preferentially. Eg : Myocardial ischemia High catecholamine state Digitalis toxicity

7. TYPE III: COMPLETE AV block – which allows ventricles to beat under subsidiary pacemakers- AV junctional / ventricular escape rhythm. Complete AV block- not synonymous with complete AV dissociation Patients with CHB – have AV dissociation Patients with complete AV dissociation may/may not have CHB

8. CHB When no atrial activity is conducted to ventricles. Atrial and ventricular activity are controlled by independent pacemakers. Atrial pacemaker- sinus/ ectopic/ AV junctional (above the block ) with retrograde atrial conduction. Ventricular pacemaker – below the level of block- above/ below his bundle bifurcation.

9. Block @ level of AV node- usually congenital Block within bundle of His / distal to His bundle in purkinje – usually acquired.

10. TYPE IV: COMBINATION OF CAUSES DIGITALIS TOXICITY- Down sloping ST depression with a characteristic “Salvador Dali sagging” appearance Junctional AV nodal tachycardia Ventricular tachycardia Conduction block Ventricular bigeminy rhythm AV dissociation

11. Complete vs incomplete avd If a single pacemaker – establish control over atria/ventricles for one beat (CAPTURE BEAT)/ Series of beats – NO AV DISSOCIATION for that period – incomplete AV dissociation Isorhythmic AV dissociation Interference AV dissociation Severe sinus bradycardia Lower level pacemaker Junctional escape rhythm Junctional / ventricular escape rhythm Sinus rate = junctional rate Faster intrinsic rate

12. complete av dissociation When atria/ventricle –fails to respond to a single impulse for 1 beat /series of beats– AV DISSOCIATION occurs for that period. COMPLETE AV dissociation- Eg : CHB, Atrial rate > ventricular rate

13. Isorhythmic av dissociation When sinus rate is slowed & junctional rate is accelerated Slowed sinus rate = accelerated junctional rhythm Atria captured by sinus impulse Ventricles by junctional impulse.

14. Interference AV BLOCK- PRIMARY- anatomical defect /abnormal refractoriness of AV node SECONDARY -AV BLOCK – due to interference with normal refractoriness of AV node IPSIDIRECTIONAL interference paroxysmal atrial tachycardia with first degree A-V block atrial flutter with 2:1 A-V block.

15. Interference av dissociation Repetitive CONTRADIRECTIONAL INTERFERENCE- AV dissociation Interference Dissociation—

16. Zone of interference

17. CHB AVD DEFINITION AV conduction All atrial impulse –blocked AV junction/ventricles – compelled to initiate alternate escape rhythm affected Ventricles dissociate itself from atria by an autonomous focus arising from AV junction/ventricles. intact PATHOLOGY Pathological AV block Degenerative , ischemic, congenital, VHD Physiological AV block Due to ill-timed accelerated lower pacemaker activity CHB VS AVD

18. CHB AVD BASIC HR Almost always in bradycardia Can occur @any HR TACHYCARDIA: Atrial tachycardia Accelerated junctional tachycardia VT All VVI pacemaker rhythm NORMAL RATE: Early stages of SND AIVR BRADYCARDIA; High vagal tone Ischemic SA/AV nodes( IWMI)

19. ATRIAL RATE VS VENTRICULAR RATE Atrial > ventricular rate Ventricular rate >/= atrial rate duration Often permanent Drug / dyselectrolytemia - reversible Often transient QRS width 50% narrow, 50% wide 90% narrow Except VT CAPTURE & FUSION BEAT Rare If present- high grade AVblock common PPI requirement Require PPI Rarely required

20. If VT is persistent – suppress SA node Atrial depolarization & contraction during VT – complex Hence P wave in VT can be Totally absent Occur antegrade On QRS Over T waves

21. AV dissociation in VT – rarely manifested. In intact VA conduction VT – traverse AV junction– reset SA node/ set in semi depolarized state.

22. CLINICAL FEATURES 1.VARYING PULSE VOLUME: Some atrial beats– contribute to ventricular filling--- varying ventricular volumes 2.REVERSE PULSUS PARADOXUS (IN ISORHYTHMIC AV DISSOCIATION): Pulse volume decrease during expiration Inspiration--- increase sinus rate – AV synchrony Expiration – decrease sinus rate – junctional rhythm takes over--AV asynchrony

23. 2. JVP-Cannon waves 3.MR/TR: Simultaneous contraction of atria & ventricle

24. management Type I : increase sinus rate with sympathomimetics Type II: control tachyarrhythmias from subsidiary pacemakers Type III : PPI TYP IV: digoxin specific Ab ( digibind / digiFab )

25. THANK YOU