Mechanism of Arrythmias - Quiz 2 Flashcards
three mechanisms of arrhythmia
- abnormal automaticity
- abnormal triggered activity
- re-entry
types of abnormal triggered activity
- early afterdepolarizations
- late afterdepolarizations
abnormal automaticity due to
- abnormal phase 4 depolarization
exclusivity of mechanisms of arrhythmia
- not mutually exclusive
abnormal phase 4 depolarization due to which conditions
- degeneration/fibrosis
- ischemia
- stretch
- hypokalemia
- sympathetic stimulation
DISH S
stretch due to
- people with CHF
EAD inciters
- QT prolonging drugs
EADs exaggerated by
- slow heart rate
- hypokalemia
EADs blunted by
- rapid heart rates
- K+, Mg2+
EADs mechanisms
- net increase inward
- plateau current
EADs putative clinical rhythm
- torsades
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early afterdepolarizations
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delayed afterdepolarizations
DADs inciters
- digitalis
- catecholamines
DADs exaggerated by
- rapid rates
DADs blunted by
- Ca2+ channel block
DADs mechanism
- intracellular Ca2+ overload
DADs putative clinical rhythm
- dig tox
- ischemia
- outflow tract VT
most common mechanism for abnormal rhythms
- reentry
what will favor re-rentry
2 heterogenous pathways
Transient or permanent unidirectional block
dispersion of refractoriness
slow conduction velocity in the normal unblocked pathway
what can result from a transient or unidirectional block
one electrical pathway has either a prolonged refractory period or a prolonged repolarization time
producing a wave which only travels down the remaining pathway.
importance of slow conduction in regions of less refractoriness
must be slow enough relative to the refractoriness of the blocked pathway to allow recovery of the previously blocked pathway.
WPW AV rentry tachycardia structural physiology
- AV bypass tracts found along muscular portion of mitral and tricuspid annulus’
- THESE ARE THE ACCESSORY TRACTS
WPW sinus rhythm due to
- fusion of bypass and AV nodal conduction to ventricle
WPW re-entry tachycardia due to
- there is a block in the bypass tract
- re-entry of impulse from AV node over bypass tract that now depolarizes backwards
how can an accessory tract depolarize again?
- the slow conduction of the AV node allows the bypass tract to recover its excitability
premature impulse in AV re-entry tachycardia due to
- unidrectional block in the bypass tract only
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where would you see this signal?
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AV re-entry tachycardia
in WPW
strategy of antiarrhythmic agents
- alter automaticity
- alter conduction velocity
- alter refractory period
antiarrythmic drugs - how we alter automaticity
ALL WAYS TO SLOW DOWN HEART RATE
- decrease slope of phase 4 depolarization
- increase threshold potential
- decrease resting membrane potential
antiarrythmic drugs - ways to alter conduction velocity
- decrease rate of rise of phase 0
- decrease resting membrane potenail and responsiveness
antiarrythmic drugs - ways to alter refractory period
- increase phase 2 plateau
- increase phase 3 repolarization
- increase action potenial duration
strategy of catheter ablation
- eliminate pathway of reentry circuit
- create barrier of conduction to disrupt reentry circuit
- eliminate source of abnormal automaticity or triggered activity
bradyarrythmias defined as
- heart rate less than 60 bpm
bradyarrythmias due to
- abnormal automaticity
- degeneration of the normal conduction system
diagnosis based on EKG
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- sinus bradycardia
p wave in sinus bradycardia
- normal p wave
conditions that can cause sinus bradycardia
- high vagal tone
- ischemia
- degenerative disease
- drugs
- hypothyroidism
HDIDH
treatment of sinus bradycardia
- no treatment unless symptomatic
- then pacemaker
diagnosis based on EKG
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- sinus pause
sinus pause cause
- degenerative disease in or around SA node
sinus pause treatment
- pacemaker if symptomatic
symptoms of sinus pause
- syncope generally greater than 3 seconds
diagnosis based on EKG
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- tachy-brady syndrome
what you see in tachy-brady syndrome
due to
- pauses occur at termination of tachyarrythmias
- due to overdrive suppression of SA node
diagnosis based on EKG
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- junctional escape rhythm
junctional escape rhythm due to
- AV nodal cells acting as subsidiary pacemaker due to slower phase 4 depolarization
hallmark of junctional escape rhythm
- no P before QRS
what you see in first degree heart block
- every P makes a QRS
- but long PR
what you see in second degree heart block
- regular P waves
- some but not all P waves makes QRS complexes
what you see in third degree heart blocks
- constant and independent atrial and ventricular rates
- no P conducts to a QRS
diagnosis based off EKG
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- 1st degree AV block
causes of first degree AV block
- high vagal tone
- degenerative disease
- drugs
treatment of first degree AV block
- nothing
which secondary AV block is most common
- mobitz 1
refractoriness of mobitz 1
varies
PR of mobitz 1
long, prolongs
usual site of block mobitz 1
- within AV node
QRS duration mobitz 1
- any
causes mobitz 1
- AV nodal blocking drugs
- inferior MI
- vagal tone
- degenerative disease
carotid massage mobitz 1
- worsens
exercise mobitz 1
- improves
permanent pacing (mobitz 1)
- not usually
refractoriness of mobitz 2
- fixed
PR of mobitz 2
- short, constant
usual site of block mobitz 2
- below the AV node
QRS duration mobitz 2
- usually wide
- usually associted with BBB
causes of mobitz 2
- Na+ channel blocking drugs
- anterior MI
- degenerative disease
carotid massage mobitz 2
- no change or improves
exercise, atropine mobitz 2
- no change or worsens
permanent pacing for mobitz 2
- yes
diagnosis based on EKG
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- mobitz 1 block
- look for P without QRS
- wide QRS
- longer PR
diagnosis based on EKG
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mobitz II
- look for P without QRS then short PR
diagnosis based on EKG
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- 3rd degree AV block
- no relationship between P and QRS
- more P’s than QRS’s. QRS’s are regular
treatment of 3rd degree AV block
- reverse with treatment of underlying cause
- may need pacemaker
cause of 3rd degree AV block
- ischemia/infarct
- degenerative disease
diagnosis based on EKG
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3rd degree AV block
- due to inferior MI
diagnosis based on EKG
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- sinus bradycardia - atrial pacing
- pacemaker spike followed by P wave
diagnosis based on EKG
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- ventricular pacing
- can see the spike of the current depolarizing the ventricle