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Arrhythmias-Narrow Complex Tachycardias Flashcards

1
Q

outline the classification of tachycardias

A
  • narrow complex
  • broad complex
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2
Q

what are narrow complex?

A

SVT’s

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3
Q

symptoms of SVT?

A
  • dizziness
  • palpitations
  • chest pain
  • collapse
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4
Q

define narrow complex

A
  • rate >100bpm
  • QRS width <120ms
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5
Q

what can SVT’s be

A
  • focal
  • re-entry
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6
Q

what are the types of focal SVT’s?

A
  • Sinus tachycardia
    • focus on SA node
  • Atrial tachycardia
    • heart’s electrical rhythm comes from an ectopic pacemaker in atria; hence a different focus in atria takes over from SA node
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7
Q

causes of sinus tachycardia?

A

numerous physiological causes…

  • fever
  • thyrotoxicosis
  • hypotension
  • hypoxia
  • any form of stress
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8
Q

aetiology of atrial tachycardia?

A
  • structural heart abnormality
  • CAD
  • lung disease
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9
Q

what is seen in atrial tachycardia on ECG?

A

abnormally shaped P waves

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10
Q

what are the types of re-entry tachycardias?

A
  • atrial flutter
  • atrial fibrillation
  • atrio-ventricular re-entrant tachycardia (AVRT)
  • atrioventricular nodal re-entrant tachycardia (AVNRT)
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11
Q

what are the 3 main types of SVT?

A
  • AVRT
  • AVNRT
  • Atrial tachycardia
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12
Q

pathophysiology of re-entry?

A

electrical signal re-enters atria from ventricles –> travels through AV node –> causes another ventricular contraction

essentially causes a self-perpetuating electrical loop without an end point & results in a fast, narrow complex tachycardia

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13
Q

describe AVRT and Rx of it

A
  • electrical signal re-enters through accessory pathway - WPW

Rx:

  1. best initial treatment: electrical cardioversion
    * curative option: ablation of pathway
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14
Q

what is contraindicated in patients with AVRT who develop AFib or Atrial Flutter?

A

AV node blockade, as by doing so you are encouraging use of accessory pathway & if there are fibrillatory waves from atria these can transmit to ventricles & cause VFib

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15
Q

describe AVNRT & Rx of it

A
  • re-entry back through AV node

Rx:

AV node blockade

  • mechanical
    • carotid sinus massage, vasovagal maneouvres
  • chemical
    • adenosine
    • beta blockers
    • verapamil (CCB)
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16
Q

ECG features of AVRT & AVNRT

A
  • AVRT- inverted P waves after QRS
  • AVNRT- no P waves seen
17
Q

Mx of pts w SVT?

A

stepwise approach trying each step & seeing if it works before moving on

make sure on continuous ECG monitoring

  • if haemodynamically compromised
    • sedate + DC cardioversion
  • if stable - identify rhythm & treat accordingly
    1. vagal maneouvres
      • valsalva
      • carotid sinus massage
    2. Adenosine
    3. Verapamil
    4. DC Cardioversion if above fails
18
Q

what should valsalva and carotid massage do?

A

terminate an SVT

19
Q

how is carotid sinus massage done?

A

massage carotid gently on one side w 2 fingers

20
Q

what is the difference between Defibrillation and Cardioversion?

A

defibrillation:

  • unsynchronised, random administration of shock throughout any point of cardiac cycle

cardioversion:

  • synchronised administration of shock during R wave / QRS complex of cardiac cycle
21
Q

how does adenosine work?

A
  • slows cardiac conduction mainly through AV node
  • interrupts AV node/accessory pathway during SVT & resets back to sinus rhythm
  • must be given as rapid bolus
  • will often cause brief period of asystole / bradycardia that can be scary
22
Q

when should adenosine be avoided?

A
  • asthma
  • COPD
  • HF
  • Heart block
  • severe hypotension
23
Q

what drug reduced function of adenosine?

A

theophylline

24
Q

what drug increases function of adenosine?

A

dipyridamole

25
when adminstering, what should you warn pt about and where is it administered into
warn about scary feeling of dying / impending doom administered into a large proximal cannula (eg grey cannula in antecubital fossa)
26
can adenosine be used in pregnancy?
yes, safe to use
27
how much adenosine is adminstered?
6mg then 12mg then a further 12mg if no improvement in between doses
28
prophylaxis of SVT?
* B Blockers, CCB or amiodarone * radiofrequency ablation
29
pathophysiology of WPW?
* extra electrical pathway connecting atria & ventricles- bundle of kent * causes no problems and is asymptomatic * when this pattern can facilitate certain arrhythmias (ie AVRT), or worsen pre-existing atrial arrhythmias--\> WPW Syndrome
30
what may happen with a pre-existing atrial arrhythmia in WPW?
atrial conduction too fast so AV node blocks it so then goes down accessory pathway --\> Vfib --\> cardiogenic shock as heart barely has time to fill up/pump blood
31
aetiology of WPW?
congenital
32
WPW on ECG?
**W**ide QRS (\>0.12seconds) **P**R interval short \<0.12seconds **W**ave- Delta wave (slurred upstroke of QRS)
33
Rx of WPW?
definitive - radiofrequency ablation of accessory pathway
34
what drugs are contraindicated in WPW pts with AFib or Atrial flutter?
anti-arrhythmics - beta blockers - CCB - adenosine
35
pathophysiology of Atrial flutter?
* caused by re-entrant rhythm in either atrium * signal goes round & round the atrium without interruption & stimulates atrial contraction at 250-300bpm * due to refractory period of AV node, signal makes its way to the ventricles every 2nd lap causing ventricular contraction at 150bpm
36
atrial flutter on ECG
* **characteristic saw tooth appearance of P waves** * QRS regular * blocks can be 2/3/4/5:1 depending on how many P waves per QRS complex
37
associated conditions with Atrial flutter?
* HT * IHD * Cardiomyopathy * thyrotoxicosis * can be precipitated by acute cardiac / respiratory problems
38
Rx of atrial flutter?
* rate /rhythm control * beta blockers / cardioversion * radiofrequency ablation of re-entrant rhythm * anti-coagulation based on CHAD2DVASC score * treat reversible underlying condition

Cardio (18 decks)

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