Download 3o AV Block

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Atrioventricular Blocks
Chapter 6
Block Sites
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Sinus Node Disorders
Sick Sinus Syndrome
• SA Node Dysfunction
• Most often in elderly patients w/ heart disease
• Marked sinus bradycardia w/o normal escape rhythm
• May develop intermittent SVT
– Brady‐tachy syndrome
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Sinus Node Disorders
AV Blocks
• Conduction block b/n SA Node and the Purkinje Fibers
• Retards or eliminates conduction from the atria to the ventricle
• 3 types
– 1st Degree
– 2nd Degree
– 3rd Degree
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1st Degree AV Block
• Delay not a block
• Prolonged delay in conduction at the AV Node
• Prolonged PR interval (> 0.2 sec)
• Every QRS preceded by P‐Wave
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1st Degree AV Block
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2nd Degree AV Block
• Not all P‐waves are conducted
–Will see non‐conducted P‐
waves
• 2 types
–Mobitz Type I (Wenckebach)
–Mobitz Type II
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2nd Degree AV Block
(Mobitz Type I ‐ Wenckebach)
• Usually block high in AV Node
• Block w/n AV node longer & longer delay until conduction does not go through usually after 3 or 4
– Not dangerous
• Gradually progressing P‐R Interval w/ eventual non‐
conducted P‐wave
2nd Degree AV Block
(Mobitz Type I ‐ Wenckebach)
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2nd Degree AV Block
(Mobitz Type I ‐ Wenckebach)
2nd Degree AV Block
(Mobitz Type I ‐ Wenckebach)
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2nd Degree AV Block
(Mobitz Type I ‐ Wenckebach)
2nd Degree AV Block
(Mobitz Type II)
• Total block below AV node (NO conduction from atria to ventricles)
• Dropped beat w/o progressive lengthening of PR interval
• EKG shows normal PR & QRS complex, then a beat will be dropped
• Block below AV Node
– May progress to complete heart block – May require a pacemaker 9
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2nd Degree AV Block
(Mobitz Type II)
2:1 AV Block
3:1 AV Block
2nd Degree AV Block
(Mobitz Type II)
2:1 AV Block
3:1 AV Block
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2nd Degree AV Block
(Mobitz Type II)
Mobitz II
Wenkebach
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Mobitz II
Mobitz II
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3o AV Block
3o AV Block
• Complete heart block……NO atrial impulses make it through to activate ventricles
• Block at AV node or lower
• Therefore, Ventricles respond by generating an escape beat at (30 to 45 b/min) • Atria rate (60 to 100 b/min) & Atria may be in any rhythm of their own
• P‐waves march out
– No relation to QRS
• Ventricles are wide because of ventricular origin
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3o AV Block
• Causes
–Degenerative disease of conduction system
–Acute MI
3o AV Block
• Can be transient
• If permanent, requires pacemaker
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3o AV Block
3o AV Block
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3o AV Block
Sinus Bradycardia w/ complete heart block & slow junctional
escape rhythm
Sinus Arrythmia w/ complete heart block & a junctional escape rhythm
3o AV Block
A‐Fib w/ complete heart block & an idioventricular‐escape rhythm
NSR w/ complete heart block & an idioventricular‐escape rhythm
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3o AV Block
Atrioventricular (AV) Dissociation
• 3rd degree AV Block
– Serious and often permanent
• AV Dissociation
– Transient and usually innocuous
– Ventricular rate may be faster than Atrial rate
– P‐wave may be periodically conducted
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3o AV Block
• AV dissociation
– Like 2 different ECGs – one atrial, one ventricular
– Atrial rate can be sinus to A‐fib
– Ventricular rate will not be affected
• Can be junctional or ventricular
AV Dissociation
QRS obliterating the P‐wave
Note: Atria rate is slower than Ventricular rate
P‐wave partially merged w QRS
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AV Dissociation
Mobitz I ‐ Wenkebach
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Mobitz II – 3:1 AV Block
Sinus Rhythm w 1st Degree AV Block Mobitz Type II – 2:1 Av Block
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3rd degree Block
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