Preexcitation and SVT Flashcards

1
Q

what are the two possible electrical pathways to the ventricles?

A

normal AV node pathway

abnormal accessory pathways (in the AV node or myocardium)

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2
Q

most common electrical pathway to ventricles

A

normal AV node pathway

alpha pathway

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3
Q

beta pathway

A

abnormal conduction pathways

av node or myocardium

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4
Q

other names for beta pathways

A

accessory pathways
bypass tracts
preexcitation pathway
aberrant pathway

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5
Q

do pts just have alpha or beta pathways?

A

they have both but beta pathways are normally dormant

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6
Q

when the beta pathways are activated what is the pt at risk for?

A

developing arrhythmias

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7
Q

triggers to activate beta pathways

A

stress, catecholamine surge
caffeine, tobacco, street drugs
electrolyte abnormalities
acid base imbalance

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8
Q

electrical properties of alpha pathway

A

slow conduction

short refractory period (fast reset)

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9
Q

electrical properties of beta pathway

A

rapid conduction

long refractory period (slow reset)

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10
Q

when a current travels the beta pathway would we expect that the ventricles would depolarize earlier or later than normal

A

earlier because of the rapid conduction

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11
Q

preexcitation

A

anytime the ventricles depolarize earlier than they were supposed to

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12
Q

preexcitation + tachycardia =?

A

form reentrant loops that lead to SVT (supraventricular tachycardia)

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13
Q

What will the PR interval look like if an accessory pathway in the AV node is activated? (normal, short, or prolonged?)

A

short

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14
Q

What will the QRS complex look like if an accessory pathway in the AV node is activated? (normal or wide?)

A

normal

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15
Q

What will the PR interval look like if an accessory pathway in the myocardium is activated? (normal, short, or prolonged?)

A

short

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16
Q

What will the QRS complex look like if an accessory pathway in the myocardium is activated? (normal or wide?)

A

wide

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17
Q

three types of preexcitation

A

wolff parkinson white
lgl syndrome
mahaim preexcitation

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18
Q

what is the accessory pathway for WPW called?

A

kent bundle

direct connection between atria and ventricle

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19
Q

what are the two things that will be on an ECG for WPW

A
short pr interval
delta wave (upward slurring of Q wave)
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20
Q

why does the delta wave occur?

A

upper ventricle is depolarized by myocardium and the rest of ventricle is depolarized by purkinje system

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21
Q

symptoms of WPW without tachycardia

A

preexcitation

asymtomatic

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22
Q

why is WPW with tachycardia a problem?

A

turns symptomatic

need to avoid ketamine, pain, hypovolemia, anxiety

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23
Q

What can WPW tachycardia be confused with on ECG?

A

ventricular tachycardia bc QRS are wide

look for delta wave

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24
Q

what are the 3 treatments for WPW

A

transvenous catheter ablation
antiarrhythmic drugs
synchronized cardioversion (if unstable)

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25
Q

what is the most effective and permanent solution for WPW?

A

transvenous catheter ablation

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26
Q

what antiarrhythmic drugs should be avoided in WPW?

A

drugs that block conduction through AV node

adenosine, calcium channel blockers, digoxin

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27
Q

what antiarrhythmic drugs can be given to pts with WPW?

A

beta blockers

amiodarone

28
Q

why do we not want to fully block the AV node?

A

then the entire conduction is going through the beta pathway and that can lead to serious arrhythmias

29
Q

Lown Ganong Levine (LGL) syndrome accessory pathway

A

james bundle

direct connection between atria and bundle of His (bypass AV node)

30
Q

activation of LGL pathway on ECG

A

short PR interval

no delta wave

31
Q

LGL syndrome symptoms

A

usually asymptomatic and no treatment required

32
Q

mahaim preexcitation accessory pathway

A

mahaim fibers
connects AV node to RV
bypass bundle of His

33
Q

ECG for mahaim preexcitation

A

normal pr interval
widened QRS
could have or not have delta wave

34
Q

technically what does SVT refer to?

A

tachycardia originating above ventricles (sinus tach, afib, aflutter)

35
Q

clincally what does SVT refer to?

A

tachycardia greater than 150bpm caused by reentry

36
Q

ECG of SVT

A

HR >150
QRS normal
difficult to differentiate between sinus and junctional tachycardia (p wave may not be present)

37
Q

symptoms of SVT

A

ventricular filling decreased

CO decreased

38
Q

paroxysmal SVT

A

SVT when it begins and ends abruptly “occuring in spasms”

39
Q

what can paroxymal SVT look like on ECG?

A

afib

40
Q

Suppose a patient has an active accessory pathway in the myocardium. When the SA node depolarizes, which pathway will the current travel to get to the ventricles?

A

travels antegrade down both alpha and beta pathways

preexcitation occurs

41
Q

Suppose that in this same patient with an active accessory pathway in the myocardium, a premature atrial contraction (PAC) occurs. From this PAC, which path will the current travel through to get to the ventricles?
4

A

1- travels antegrade down the alpha pathway (because it has a short refractory period)
2- accessory pathway repolarizes when impulse is traveling down av node
3- travels retrograde through accessory pathway
4- travels antegrade through the alpha pathway again
REENTRANT LOOP

42
Q

what does the reentrant loop in the myocardium look like on ECG?

A

delta wave

wide QRS

43
Q

what does the reentrant loop in the av node look like on ECG?

A

normal QRS complex

44
Q

what is the most common type of reentry?

A

SVT in AV node

AV Nodal Reentrant Tachycardia (AVNRT)

45
Q

ECG for AVNRT

A

narrow QRS

may or may not have p wave

46
Q

treatments for SVT in AV node (AVNRT) that slow conduction of AV node

A

vagal maneuvers
adenosine
calcium channel blockers
digoxin

47
Q

vagal maneuver

A

valsalva- ask pt to blow through a straw
carotid massage
cold stimulus

48
Q

when should you avoid a carotid massage? why?

A

could dislodge plaque

avoid in geriatric, high cholesterol, previous stroke

49
Q

pharmacology of adenosine

A

5-10 sec acting

uncomfortable for pt (can stop heart)

50
Q

dose of adenosine

A

inital 6mg bolus

up to 2 more doses of 12mg

51
Q

what does sotalol do?

A

beta blocker

increases refractory period in AV node

52
Q

dose for sotalol to treat SVT?

A

100mg or 1.5mg/kg

53
Q

when should sotalol be avoided?

A

pts with prolonged QT syndrome

54
Q

full list of treatment for SVT within the AV node

A
slow conduction through AV node
antiarrhythmics
beta blocker
synchronized cardioversion
transvenous catheter ablation
55
Q

what is SVT in the myocardium referred to as?

A

atrioventricular reentrant tachycardia (AVRT)

56
Q

ECG for AVRT

A

p waves

possible delta waves

57
Q

Is AVRT the same thing as Wolff Parkinson White?

A

WPW can become AVRT if has tachycardia

58
Q

treatment for SVT within myocardium

A

antiarrhythmics
beta blockers
synchonized cardioversion
transvenous catheter ablation

59
Q

should you avoid av node blockers in AVRT?

A

yes

60
Q

what is the treatment option for people who have arrhythmias (usually afib) that are unrespinsive to medications

A

doctors map area that is causing the disturbance and ablate the abnormal conduction pathways

61
Q

what does the maze procedure treat?

A

afib

62
Q

maze procedure

A

surgeon inflicts scar tissue by many means to disrupt abnormal conduction pathways

63
Q

is the maze usually done alone?

A

no it is usually combined with another heart operation and is performed while sternotomy or thoracotomy

64
Q

left atrial appendage closure

A

prevent clot release from LA in pts with afib

65
Q

options for left atrial appendage closure 2

A

1 ligation of left atrial appendage (open heart)

2 intertion of watchman device (endovascular)