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TAS Cardiology > Arrhythmias > Flashcards

Arrhythmias Flashcards

1
Q

What is the most common type of tachycardia seen in children?

A

Narrow complex tachycardia

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2
Q

What is a narrow complex tachycardia?

A

Any arrhythmia that originates above or at the bundle of His

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3
Q

What is the HR in SVT?

A

220-300bpm

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4
Q

What is the clinical relevance of SVT in an individual patient related to?

A
  • Ventricular rate
  • Presence of any underlying heart disease
  • Integrity of any cardiovascular reflexes
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5
Q

How does SVT typically present in young infants or neonates?

A

Symptoms of heart failure

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6
Q

What can SVT cause in utero?

A
  • Hydrops fetalis

- Intrauterine demise

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7
Q

What might it be difficult to differentiate SVT from in the paediatric population?

A

Sinus tachycardia

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8
Q

What features might suggest a tachycardia is sinus tachycardia?

A
  • Child may have systemic illness
  • HR rarely >200bpm
  • P wave upright in leads II, III< and aVF
  • Beat to beat variability
  • HR slows with treatment/fluid resus
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9
Q

What features might suggest a tachycardia is SVT?

A
  • Previously well with no preceding systemic upset
  • HR generally >220bpm
  • P waves may be absent or negative in leads II, III, and aVF
  • No beat to beat variability (fixed RR interval)
  • Rate abruptly changes with adenosine
  • Sudden onset
  • May have had previous episodes
  • Little change in rate with activity, crying, or breath holding
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10
Q

What is the probability of complete resolution of SVT dependent on?

A

The age of onset

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11
Q

What % of cases of SVT resolve when diagnosed at 1 year of age or less?

A

> 90%

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12
Q

What % of cases of SVT resolve when diagnosed after 1 year of age?

A

33%

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13
Q

What can SVT be divided into groups on the basis of?

A

If they arise from the atria or the atrioventricular junction

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14
Q

What can help in SVT?

A
  • Carotid sinus massage

- Administration of IV adenosine

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15
Q

How does carotid sinus massage or administration of IV adenosine help in SVT?

A

It increases the atrioventricular block

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16
Q

Why might carotid sinus massage/administration of IV adenosine be of diagnostic value in SVT?

A

It allows for more accurate visualisation of the atrial activity

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17
Q

What type of SVT arrhythmias arise from the atria or SA node?

A

Atrial fibrillation or flutter

18
Q

What is atrial fibrillation caused by?

A

Multiple re-entrant circuits triggering waves of activation in the atria

19
Q

What does atrial fibrillation look like on ECG?

A
  • Irregular baseline made up of fibrillation waves
  • Absent P waves
  • Conduction of atrial impulses to the ventricles is variable, resulting in irregular RR interval
20
Q

What is atrial flutter caused by?

A

Re-entry circuit in right atrium with secondary activation of the left atrium

21
Q

What is the atrial rate in atrial flutter?

A

About 300bpm

22
Q

How does atrial flutter appear on ECG?

A

Saw-toothed flutter waves

23
Q

What does the ventricular rate depend on in atrial flutter?

A

The rate of conduction through the AV node

24
Q

What is the typical rate of conduction through the AV node in atrial flutter?

A

2:1

25
Q

What is the typical ventricular rate in atrial flutter if the rate of conduction is 2:1?

A

150

26
Q

What is the most common type of SVT seen in children?

A

AV re-entry tachycardia (AVRT)

27
Q

What is AVRT also known as?

A

Accessory pathway mediated tachycardia

28
Q

What % of arrhythmias occurring during infancy are AVRT?

A

80%

29
Q

What does AVRT involve?

A

An electrical re-entry circuit

30
Q

Describe the electrical re-entry circuit in AVRT?

A

The circuit proceeds down the AV node, and then up an accessory pathway outside the AV node

31
Q

What kind of rhythm does AVRT produce?

A

A narrow complex tachycardia

32
Q

What % of patients with AVRT have Wolff-Parkinson-White syndrome?

A

50%

33
Q

How can WPW syndrome be differentiated from others with AVRT?

A

In WPW syndrome, even in sinus rhythm they manifest ventricular pre-excitation in the form of a delta wave on the ECG. The remainder have a ‘concealed’ pathway which is not evident on the ECG during sinus rhythm

34
Q

What are the ECG features of WPW syndrome?

A
  • Delta wave
  • Shortened PR interval
  • Slurred QRS upstroke
  • Widened QRS
35
Q

What causes the PR and QRS changes seen in WPW syndrome?

A

Conduction through the accessory pathway can occur before the AV node is activated

36
Q

What is the result of conduction through the accessory pathway before AV node activation being possible in WPW syndrome?

A

It creates the potential for rapid ventricular response during atrial fibrillation

37
Q

What can rapid ventricular response during atrial fibrillation result in?

A

Ventricular fibrillation and sudden death

38
Q

What drug should not be given in WPW?

A

Digoxin

39
Q

Why should digoxin not be given in WPW?

A

As it can enhance conduction through the bypass tract, whilst slowing down conduction through the AV node, and this may trigger VF

40
Q

How is acute SVT managed in WPW?

A

Same as for patients in concealed and manifest pathways

41
Q

What is recommended due to the risk of VF in WPW?

A

Definitive ablative therapy

TAS Cardiology (7 decks)

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