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Clin Med - Cardio II > Conduction Blocks > Flashcards

Conduction Blocks Flashcards

1
Q

3 types of AV blocks

A

1st degree - AV synchrony maintained
2nd degree - intermittent loss of AV conduction
3rd degree - AV dissociation

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2
Q

2 major etiologies of AV blocks

A
  1. progressive cardiac conduction dz - 50% - fibrosis or sclerosis
  2. ischemic heart dz - 40%
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3
Q

other etiologies of AV block

A
  1. trained athlete - increased vagal tone
  2. infiltrative process - amyloidosis, sarcoidosis
  3. CHF
  4. myocarditis
  5. familial dz
  6. meds
  7. malignancies
  8. cardiac surgery
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4
Q

what is 1st degree AV block

A

prolonged PR interval - delay in AV conduction (>0.2sec)
ratio of P to QRS waves 1:1
unlikely to change to 2nd degree
PR interval should be consistent, but consistently long

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5
Q

etiology of 1st degree AVB

A

increased vagal tone
underlying structural abnormalities
drugs that impair AV conduction - BB, CCB, digoxin

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6
Q

populations affected by 1st degree AVB

A
  1. trained athletes 8%
  2. African Americans>whites
  3. increases with age
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7
Q

severity of first degree AVB

A

usually asymptomatic
benign
increases risk of afib
more likely to require pacemaker later in life
in pts with stabile coronary dz, increases risk of hospitalization for heart failure

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8
Q

if PR interval is

A

no treatment

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9
Q

if wide QRS complex, delay AV node, uncertain progression, how to manage 1st degree AVB?

A

refer to electrophysiologist for consideration of pacemaker

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10
Q

what is an AV block

A

delay or transmission of electrical current from atria to ventricles

  • can be anatomical or functional
  • can be transient or permanent
  • many causes
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11
Q

how to treat 1st degree AVB

A
  • avoid AV blocking agents

- treat underlying dz

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12
Q

what is 2nd degree AVB

A

ratio of p waves to QRS is >1:1

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13
Q

two types of 2nd degree AVB

A
  1. Mobitz I - Wenckebach

2. Mobitz II

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14
Q

prevalence of 2nd degree AVB

A

US - .003%
-significantly higher in trained athletes
3% of pts with structural defects will develop 2nd degree AVB
men= women

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15
Q

etiologies of 2nd degree AVB

A

cardiac meds
lithium
inflammatory dz - incld lyme, endocarditis
infiltrative dz - amyloidosis, sarcoidosis
malignancies
collagen vascular dz - sclerodoma

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16
Q

workup for 2nd degree AVB

A 
EKG
electrolytes
lyme titers
digoxin levels
cardiac biomarkers
echo
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17
Q

what is Mobitz type I

A

aka Wenckebach

  • progressively lengthening of PR interval until there is a dropped beat
  • cycle repeats
  • rarely progresses to complete heart block
  • not considered abnormal in athletes
18
Q

s/s of Mobitz type I AVB

A 
typically asymptomatic
fatigue
lightheadedness
syncope
angina
heart failure
19
Q

treatment of Mobitz Type I AVB

A

treat underlying cause (avoid AV nodal blocking meds)
no specific tx required for asymptomatic pts
monitor EKG periodically for progression to type II
if syncope or other symptoms - refer to EP. if marked prolongation of AV conduction - consider pacemaker

20
Q

what is 2nd degree AVB Mobits Type II

A
  • indicative of underlying dz of the His PUrkinje systm (below AV node)
  • more serious dz
  • episodic and unpredictable failure of the pathway to conduct impulse from atria to ventricles
  • no change in PR interval (PR interval stays same length then all of a sudden there is a dropped beat)
  • the more unpredictable the more likely it will progress to complete heart block
21
Q

what is high grade second degree AV block Mobitz type II

A

2 dropped beats in a row

22
Q

s/s of Mobitz type II

A

symptoms range from none to many depending on rate an frequency of dropped beats

  • if slow rate or frequent dropped beats = reduced CO
  • fatigue
  • lightheadedness
  • syncope
23
Q

treatment of Mobit type II

A

frequently progresses to third degree AV block
treat underlying cause
avoid AV nodal blocking meds
pacemaker indicated in nearly all pts - refer!

24
Q

WHAT IS THIRD DEGREE AVB

A

COMPLETE FAILURE OF AV NODE TO CONDUCT ANY IMPULSES FROM THE ATRIA TO THE VENTRICLES

  • VARIABLE PR INTERVALS
  • INTRINSIC DZ OF THE AV NODE OR HIS-PURKINJE SYSTM
  • ESCAPE RHYTHM (JUNCTIONAL OR VENTRICULAR)
  • ELECTRICAL WAVE IS NOT REACHING THE VENTRICLES SO VENTRICLES ARE FIRING INDEPENDENTLY FROM ATRIA
  • P WAVES WILL BE CONSISTEN INTERVALS AND QRS WILL BE CONSISTENT INTERVALS, BUT NOT RELATED
25
Q

locations of 3rd degree heart block

A
  1. AV node = narrow complex
  2. bundle of HIS = narrow complex
  3. proximal L & R bundle brances = wide complex
  4. R bundle & L fascicles = wide complex
26
Q

epidemiology of complete heart block

A

US - 0.02%
increases with age, typically as a result of ischemic hart dz
-an early peak in incidence occurs in infancy and early childhood due to congenital complete av block

27
Q

the more distal the AV block

A

the slower the rate and more likely to cause syncope

28
Q

clinical manifestations of 3rd degree Av blocks

A
  1. chest pain - in setting of MI
  2. lightheadedness
  3. fatigue, weakness, exertional dyspnea
  4. bradycardia
  5. ventricular tachy
  6. ventricular fib
  7. asystole/sudden death
29
Q

workup for 3rd degree AVB

A

same as 2nd degree AVB

30
Q

tx of 3rd degree AV block

A

apply temporary pacer, refer to EP
treat underlying cause
avoid meds that block av node
permanent pacemaker placement in all pts

31
Q

what is a left bundle branch block?

A
  • delay in left ventricular depolarization
  • widened QRS complex >0.12s
  • characteristic morphology
  • broad R waves in V1-V6 and broad S waves in right leads (AVR)
32
Q

LBBB outcomes

A
  • difficult to ID myocardial ischemia and infarction bc of ST-T abnormalities
  • does not predict poor health outcomes in young, healthy pts
  • in older pts increases mortality
  • is an independent predictor of all cause mortality in pts with CAD
33
Q

new LBBB in the setting of chest pain is a what until proven otherwise

34
Q

development of LBBB during acute MI is associated with what

A

increased short term and increased long term mortality

35
Q

LBBB is associated with lower ventricular ejection fractions =

A

development of heart failrue

36
Q

evaluating a pt with LBBB

A
  1. echo

2. assess for CAD, stress testing

37
Q

associated conditions in LBBB:

A

HTN
CAD
valvular dz
cardiomyopathies

38
Q

tx of LBBBB

A

if young and asymptomatic and no CAD = no tx

  • treat underlying conditions
  • manage and risk reduction in coronary artery dz, consider pacemaker for pts with syncope
39
Q

what is RBBB

A

wide QRS complex, r-R(prime) morph V1-V3
generally asymptomatic
not associated with any medical conditions
should be able to diagnose acute MI even with RBBB
typically do not require further diagnostic eval
consider pacemaker if syncope occurs

40
Q

RBBB is associated with some conditions:

A

cor pulmonale

pulm embolism

Clin Med - Cardio II (12 decks)

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