Narrow complex tachycardias

Question 1

define supraventricular tachycardia

Answer 1

Regular narrow-complex tachycardia that originates above the atrioventricular node

Question 2

Types of supraventricular tachycardia

Answer 2

Focal
- Sinus tachycardia
- Atrial tachycardia
- Multifocal tachycardia
Re-entry
- Atrial flutter
- Atrial fibrillation
- AV Re-entry tachycardia (AVRT)
- Atrioventricular nodal re-entry tachycardia (AVNRT)

Question 3

Aetiology of focal SVTs

Answer 3

Sinus tachycardia: sinoatrial node becomes autonomic and causes a regular tachycardia
Atrial tachycardia: Often seen in chronic lung disease e.g. COPD, 100bpm and regular
Multifocal tachycardia: multiple focal points

Question 4

Aetiology of atrial flutter

Answer 4

Macro-re-entrant, single large re-entry circuit around the atrium which stimulates the AV node every time it passes. As the circuit is fixed, the rate of atrial contraction is constant

Question 5

What is an AVRT

Answer 5

normal AV Conduction + accessory pathway.

Anterograde (atria to ventricles) → pre-excitation on ECG
Retrograde (ventricle to atria) → not seen on ECG

Orthodromic: Down the AV node and up the accessory pathway
Antidromic: Down the accessory pathway and up the normal AV conduction
= Wolff-Parkinson-White syndrome

Question 6

What is an AVNRT

Answer 6

re-entry circuit around the AV node + palpitations

Question 7

Risk factors for SVTs

Answer 7

Nicotine
Alcohol
Caffeine
Previous MI
Digoxin toxicity/excess
Paediatric congenital heart disease
Cardiomyopathy
Hyperthyroidism

Question 8

Symptoms of SVT

Answer 8

Asymptomatic OR

Abrupt onset:
* Palpitations
* Syncope
* Polyuria
* Dyspnoea
* Dizziness
* Chest discomfort
* Anxiety
Abrupt termination

Sensation of a regular rapid pounding in the neck is highly suggestive of AVRT

Question 9

What is seen on ECG in SVT

Answer 9

Narrow complex tachycardia, buried P waves in Q waves

Irregular = AF
Regular:
P waves visible → sinus tachy, atrial flutter
No P waves visible → AVNRT or AVRT

Correction → Delta waves
Preexcitation on the ECG and paroxysmal narrow complex tachycardia = Wolff-Parkinson-White Syndrome.

Question 10

Management for focal tachycardias

Answer 10

Treat cause
Severe only: Beta blocker or ivabradine (sinus node blocker)
Atrial tachycardia: beta blocker or CCBs

Question 11

Management for stable SVT

Answer 11

1. Supportive
   - Sats low → O2
   - IV access
   - 12 lead ECG
2. ?adverse signs (shock, syncope, heart failure, chest pain/ischaemia on ECG)

No
3. Is rhythm stable?
NO → AF
Yes
4. Vagal manoeuvre (valsalva)
5. Adenosine 6mg IV (asthmatic → verapamil)
6. Adenosine 12mg IV (after 2 mins)
7. Repeat adenosine 18mg
8. Metoprolol/amiodarone/digoxin IV OR sedate + cardiovert

Question 12

Management for unstable SVT

Answer 12

1. Supportive
   - Sats low → O2
   - IV access
   - 12 lead ECG
2. ?adverse signs (shock, syncope, heart failure, chest pain/ischaemia on ECG)

Yes
3. Seek senior support
4. Sedate
5. SYNCHRONISED DC shocks
- 70-120J for the first
- 120-360J for the next 2
6. Correct electrolytes, exp. K/Mg/Ca
7. Amiodarone 300mg IV over 20 mins → consider repeat shock → 900mg/24h IV via central line

Question 13

What is the role of vagal manoeuvres in SVT

Answer 13

Vagal manoeuvres = valsalva, carotid sinus massage, admin of IV adenosine

Vagal manoeuvres cause slowing within the AV node
If AV block occurs, the tachycardia will terminated and prove that part of the circuit involves the AV node
Only AVNRT and AVRT have the AV node as an integral part of the circuit

Question 14

Long term management for AVRT

Answer 14

Avoid AV node blockade e.g. digoxin, verapamil, bisoprolol
Electrical cardioversion or Flecainide to chemically cardiovert
Counselling towards an catheter ablation procedure with a high chance of cure