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methods 1 > 6. Preexcitation and SVT > Flashcards

6. 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

when a beta pathway is activated, does the current continue to flow to the alpha pathway?

A

yes - the current goes to both alpha and beta

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12
Q

preexcitation

A

anytime the ventricles depolarize earlier than they were supposed to

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13
Q

preexcitation + tachycardia =?

A

form reentrant loops that lead to SVT (supraventricular tachycardia)

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14
Q

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

A

short

due to rapid conduction in beta pathway

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15
Q

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

A

normal

signal travels through normal conduction pathways in ventricles

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16
Q

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

A

short

rapid conduction through beta pathway

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17
Q

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

A

wide (delta wave)

upper vent depolarized by myocardium and rest of vent by purkinje (Fast)

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18
Q

2 types of preexcitation

A

wolff parkinson white
lgl syndrome

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19
Q

what is the accessory pathway for WPW called?

A

kent bundle

direct connection between atria and ventricle

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20
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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21
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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22
Q

symptoms of WPW without tachycardia

A

preexcitation

asymtomatic

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23
Q

why is WPW with tachycardia a problem?

A

turns symptomatic

need to avoid ketamine, pain, hypovolemia, anxiety

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24
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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25
Q

what are the 3 treatments for stable SVT/AVRT

A

transvenous catheter ablation
beta blockers
antiarrhythmic drugs

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26
Q

what is the treatment for unstable SVT/AVRT

A

synchronized cardiaoversion

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27
Q

what is the most effective and permanent solution for WPW?

A

transvenous catheter ablation

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28
Q

what antiarrhythmic drugs should be avoided in SVT/AVRT?

A

drugs that block conduction through AV node

adenosine, calcium channel blockers, digoxin

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29
Q

what antiarrhythmic drugs can be given to pts with SVT/AVRT?

A

beta blockers

amiodarone

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30
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

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31
Q

Lown Ganong Levine (LGL) syndrome accessory pathway

A

james bundle

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

32
Q

activation of LGL pathway on ECG

A
  • short PR interval
  • NO delta wave
33
Q

LGL syndrome symptoms

A

usually asymptomatic and no treatment required

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 loops/beta pathways

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”

irregularly irregular with p waves

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- impulse goes through slow alpha pathway (bc beta pathway from previous beat is still in refractory)
2- beta 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

the majority of SVT originates in

A

SVT in AV node

AV Nodal Reentrant Tachycardia (AVNRT)

45
Q

incidence of AVNRT vs AVRT

A

AVNRT is 2x AVRT

46
Q

ECG for AVNRT

A

narrow QRS

may or may not have p wave

47
Q

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

A

vagal maneuvers
adenosine
calcium channel blockers
sotalol
digoxin
amiodarone

48
Q

vagal maneuver

A
  • valsalva- ask pt to blow through a straw
  • carotid massage
  • cold stimulus
49
Q

when should you avoid a carotid massage? why?

A

could dislodge plaque

avoid in geriatric, high cholesterol, previous stroke

50
Q

pharmacology of adenosine

A

5-10 sec acting

uncomfortable for pt (can stop heart)

51
Q

dose of adenosine

A

inital 6mg bolus

up to 2 more doses of 12mg

52
Q

what does sotalol do?

A

beta blocker
antiarrythmic

slow conduction in AV node
suppress ventricular ectopy

53
Q

dose for sotalol to treat SVT?

A

100mg or 1.5mg/kg

54
Q

when should sotalol be avoided?

A

pts with prolonged QT syndrome

55
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
56
Q

what is SVT in the myocardium referred to as?

A

atrioventricular reentrant tachycardia (AVRT)

57
Q

ECG for AVRT

A

p waves

possible delta waves

58
Q

Is AVRT the same thing as Wolff Parkinson White?

A

WPW can become AVRT if has tachycardia

59
Q

treatment for SVT within myocardium

A

antiarrhythmics
beta blockers
synchonized cardioversion
transvenous catheter ablation

60
Q

should you avoid av node blockers in AVRT?

A

yes

61
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

62
Q

cardiac ablation goes into the heart via _______ access

A

femoral vein

63
Q

if you need to ablate the Left side of heart, what does the surgeon do?

A

creates a hole in the interartrial septum

64
Q

monitoring for cardiac ablation cases?

A

central line
arterial line

65
Q

what side of the heart is more risky for cardiac ablation?

A

left side

66
Q

what additional items do we place during cardiac ablation cases?

A

OG tube w/special stylet
LET esophageal temp probe

67
Q

what does the LET probe measure

A

esophageal temperature during posterior left atrium ablation

68
Q

what drug do you avoid in cardiac ablation?

A

lidocaine
(suppresses ectopy)

69
Q

when should you avoid paralytics in cardiac ablation?

A

if surgeon is using cryoablation, to avoid phrenic nerve injury

70
Q

when will the cardiologist ask for apnea during cardiac ablation?

A

when ablating near the carina

71
Q

what MAP should you keep during cardiac ablation?

A

> 60mmHg

72
Q

when should you alert surgeon of temperature changes during cardiac ablation?

A

> 0.5C changes in temp during posterior wall ablation

73
Q

what infusion is started at end of cardiac ablation?

A

isoproterenol infusion

74
Q

SE of isoproterenol infusion?

A

dramatic BP decrease
treat w/phenylephrine

75
Q

kent bundle pathway

A

RA to RV

76
Q

james bundle pathway

A

RA to BoH

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