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heart blocks and pacers

Terms in this set (42)

first degree AV block
-characteristics
partial block, delayed AV node conduction
-*prolonged PR interval (>0.20 seconds)*
-p-wave and QRS have 1:1 relationship
-regular R-R; regular P-P
-QRS <0.12 seconds
first degree AV block
-causes
-increased vagal tone
-inferior MI
-cardiac surgery
-myocarditis
-electrolyte disturbances
-drugs that block AV node conduction
first degree AV block
-symptoms
typically asymptomatic
second degree AVB type 1 (wenckebach)
-characteristics
partial heart block
-*PR gradually lengthens until a QRS is dropped (non-conducted p wave)*
-P-P interval usually constant
-tends to repeat in a ratio of P:QRS groups (pattern)
second-degree Mobitz Type 1 AVB (wenckebach)
-origin
-etiology
origin (different origin than Mobitz II)
-malfunctioning AV node cells get tired
-eventually fail to conduct an impulse (this is why we drop a QRS)

etiology
-same as 1st degree AV block
second-degree Mobitz Type 1 AVB (wenckebach)
-symptoms
-most are asymptomatic, usually hemodynamically stable
-if symptomatic: lightheaded, signs of decreased CO
second-degree Mobitz Type 1 AVB (Wenckebach)
-treatments
if symptomatic
-may give atropine (relieves symptoms)
-pacing is rare but is 2nd line therapy after atropine
second-degree mobitz II (AVB type II)
-describe
-failure of conduction at the Bundle of His (below the AV node)
-sudden and unexpected failure of His-Perkinje cells
-intermittent non-conducted P waves (missing QRS)
-PR remains constant in PR interval of conducted beats
-P to P is regular; sometimes has a QRS fire, sometimes it does not
second degree Mobitz II (AVB type II)
-characteristics
-usually wide QRS >0.12
-R to R often irregular
-usually have LBBB or bifascicular block
-may have a pattern (2:1 block or 3:1)
-doesn't elongate before the block
second degree mobitz II (AVB type II)
-etiology
-anterior MI (elevation of V leads)
-idiopathic fibrosis of conduction system
-autoimmune
-infiltrative myocardial disease
-same as 1st degree and 2nd degree mobitz type 1
second degree mobitz II (AVB type II)
-symptoms
tend to be more symptomatic
-bradycardia, syncope, and hemodynamic instability
-likely to progress to 3rd degree AV block; can be very detrimental to patients
second degree mobitz II (AVB type II)
-treatment
discontinue any AV node prolonging drugs
1st: atropine (to increase HR and relieve symptoms)
2nd: pacing to reestablish adequate HR
-transcutaneous, transvenous, or epicardial
3rd: epi or dopamine to increase BP and HR
long term: permanent pacemaker (AICD)
third degree (complete) AVB
-describe
-complete absence of AV conduction (top and bottom parts of heart are not communicating at all; no relationship btwn p wave and qrs complex)
-independent atrial and ventricular rates (don't communicate)= AV dissociation
--SA node impulses= p wave
--accessory/intrinsic pacemaker of ventricles= QRS complexes (very slow rate 30-50 bpm; this is not normal, but is something that will sustain life until we can intervene)
-progression of 2nd degree mobitz 1 or mobitz 2
-highest risk for asystole and sudden cardiac death
third degree (complete) AVB
-characteristics
-R-R will be regular: ventricular rate differs from atrial rate
-P-P wave will be regular: atrial rate differs from ventricular rate
-QRS may be >0.12
-PR interval will vary given dissociation
-P-wave and QRS usually have no association with each other
third degree (complete) AVB
-etiology
same as 1st degree, 2nd degree type 1 and 2
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