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- Y6 Cardiovascular > Supraventricular tachycardia (SVT) > Flashcards

Supraventricular tachycardia (SVT) Flashcards

1
Q

Define supraventricular tachycardia.

A

A regular, narrow-complex tachycardia with no p waves and a supraventricular origin (arising from a discrete area in the atria)

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2
Q

How common are paroxysmal SVTs?

A
  • Uncommon
  • Can occur in all age groups
  • Most common type of SVT is AVNRT - more common in women in 20-30yrs

PSVT consists of atrial tachycardia, AVNRT, AVRT.

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3
Q

What are the causes of SVT?

A

Underlying pathology:

  • Cardiomyopathy
  • Ischaemic heart disease
  • Previous cardiac surgery
  • Hyperthyroidism

No underlying pathology:

  • Drugs - amphetamines, cocaine, acute alcohol intoxication
  • Digoxin toxicity (AV nodal block)
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4
Q

What are the other types of supraventricular tachycardias?

A
  1. Atrial fibrillation.
  2. Paroxysmal supraventricular tachycardia (PSVT) - AVRT, AVNRT and junctional tachycardias. The term SVT commonly refers to this.
  3. Atrial Flutter & Atrial Tachycardia.
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5
Q

What is the difference between AVNRT and AVRT?

A

AVNRT - AV nodal re-entry tachycardia - local circuit forms around the AV node

AVRT - AV re-entry tachycardia - re-entry circuit forms between the atria and ventricles due to presence of an accessory pathway (bundle of Kent)

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6
Q

What is atrial tachycardia?

A

Arises from small area of tissue anywhere in the atria of the heart and starts to drive the heart to beat faster than the natural pacemaker.

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7
Q

What are the symptoms of SVT?

A
  • HR between 140-200bpm
  • Palpitations
  • Dizziness
  • Dyspnoea
  • Chest discomfort/angina may be triggered by SVT
  • Time between SVTs can vary greatly
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8
Q

What are the signs of SVT on ECG?

A

During tachycardia:

  • Regular rhythm
  • Narrow complex tachycardia
  • Absent p waves

After termination of SVT:

  • AVNRT = normal
  • AVRT = “delta wave” - slurred upstroke on QRS complex
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9
Q

What is an accessory pathway producing a delta wave on ECG called?

A

Wolff-Parkinson-White Syndrome

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10
Q

How do you manage SVT?

A
  1. Is the patient haemodyamically stable?
    • No –> synchronised DC cardioversion
    • Yes –> 2
  2. Vagal maneouvres - did it work?
    • Yes -.
    • No –> 3
  3. A. IV adenosine 6mg - did it work?
    • Yes -.
    • No –> 3b then 3c then 4
      • 3B IV adenosine 12mg
      • 3C IV adenosine 18mg
  4. Choose from:
    • IV beta-blocker
    • IV amiodarone
    • IV digoxin
    • synchronised DC cardioversion
  • Radiofrequency ablation long-term.
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11
Q

When is adenosine contraindicated and what can be used instead?

A

Adenosine CI in asthma

USE VERAPAMIL

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12
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A
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14
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15
Q

What is shown on this ECG and what does it suggest?

A
  • T-wave inversion in aVL
  • Absent P waves
  • Rate 180/min
  • Regular, narrow complex tachycardia

This is therefore a supraventricular tachycardia. There are no discernible P waves and therefore the differential diagnosis includes atrioventricular nodal reentry (AVNRT) or atrioventricular reciprocating tachycardia (AVRT) associated with an accessory pathway.The lack of P waves excludes sinus tachycardia and atrial flutter (no flutter waves). It is not broad complex (excluding VT) and is not irregular (excluding AF).

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16
Q

What is the effect of IV adenosine?

A

Causes slowing within the AV node

This is also how carotid sinus massage works.

17
Q

Name 3 different maneouvres which can be used in SVT.

A
  • Valsalva maneouvre - blowing into an empty syringe
  • Sticking fingers down throat
  • Dipping face in cold water (diving reflex)
  • Pressing hard on eyeballs
  • Swallowing crushed ice/cold drink
  • Carotid sinus massage

These all stimulate the vagus nerve and cause AV nodal conduction slowing and so may terminate arrhythmias.

18
Q

What abnormalities are shown?

What is this condition ?

  1. Normal variant
  2. Sick sinus syndrome
  3. Wolff-Parkinson-White syndrome
  4. Long QT syndrome
  5. Hyperkalaemia
  6. Torsade de pointes tachycardia
A
  • Short PR interval (pre-excitation),
  • slurred upstroke to QRS (delta wave)
  • and broad QRS are present on the ECG.

This is WPW syndrome - because of preexcitation on ECG and paroxysmal narrow complex tachycardia (AVRT symptoms) is WPW. Due to prresence of an accessory pathway that links the atria and ventricles. Left sided is more common. IMPORTANT because if they develop AF in this syndrome, it will be conducted rapidly down the accessory path and can cause VF and sudden death (?FH). So must refer to cardiologist to ablate this pathway to cure them of the syndrome.

  • Hyperkalaemia = tall tented T waves, wide QRS, absent P waves and “sine wave” appearance*
  • Torsades de pointed = VT with a varying access due to a raised DT interval*
19
Q

Simply, how can you distinguish between VT and SVT on an ECG?

A

SVT - narrow complex

VT - wide complex

20
Q

Cardio placement

What is the normal PR interval and QRS size? When does the ST segment stop?

A

PR interval = <5 small squares (<200ms)

QRS = <3 small squares (<120ms)

ST segment stops before the T wave starts

21
Q

What is this diagram called?

A

Einthoven’s triangle

22
Q

What is the normal heart axis?

A

-30 to 90 e.g. leads 2 and 3 pointing downwards means left axis deviation

23
Q

Which lead should have the largest positive deflection in normal cardiac axis?

A

Lead II as this is closest to the direction in which the heart sits

Most negative should be aVR as this sits in the opposite direction

24
Q

What does the size of the QRS tell us about where the problem is?

A

Broad QRS = problem coming from ventricle

Narrow QRS = problem coming from above the ventricle

25
Q

What is shown? What is the pathophysiology?

A

P pulmonale - peaked P wave in leads II/III due to right atrial enlargement

26
Q

What is shown? What is the pathophysiology?

A

P mitrale - depolarisation of the left and right atria is shown; left atrium is markedly enlarged, such as in mitral valve stenosis.

- Y6 Cardiovascular (47 decks)

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