AV dissociation occurs when the atria and ventricles contract independently due to impaired conduction between the two. It is caused by one of three mechanisms: 1) conduction block at the AV node, 2) interference from an accelerated lower pacemaker like VT or AVNRT, or 3) complete heart block. There are four types of AV dissociation based on cause. Type I occurs when sinus bradycardia allows an escape junctional rhythm. Type II is due to acceleration of a latent pacemaker. Type III is complete heart block. Type IV is a combination of causes like digitalis toxicity leading to various arrhythmias and conduction abnormalities.

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

7. • 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

9. 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

10. 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.

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

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

13. 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

14. 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

17. 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.

18. 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.

19. INTERFERENCE AV DISSOCIATION
• Repetitive CONTRADIRECTIONAL INTERFERENCE- AV dissociation
Interference Dissociation—

20. ZONE OF INTERFERENCE

22. 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

23. 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)

24. 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

25. 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

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

27. 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

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

29. 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)

30. THANK YOU