Arrhythmias - Supraventricular Tachycardia (SVT)

Question 1

Aetiology of Supraventricular Tachycardias.

Answer 1

Electrical signal re-enters atria from the ventricles, into a self-perpetuating electrical loop without an end point, resulting in a narrow complex tachycardia (QRS < 0.12s).

Question 2

What is Paroxysmal SVT?

Answer 2

A situation where SVT reoccurs and remits in the same patient over time.

Question 3

What are the 3 types of SVT?

Answer 3

Based on electrical signal :
1. AV Nodal Re-Entrant Tachycardia (AV Node Re-Entrant).
2. AV Re-Entrant Tachycardia (Accessory Pathway Re-Entrant).
3. Atrial Tachycardia (ectopic (not SA) signal).

Question 4

Acute Management of Stable SVT (5).

Answer 4

1. CONTINUOUS ECG MONITORING :
2. Valsalva Manouevre.
3. Carotid Sinus massage.
4. IV Adenosine (or Verapamil).
5. DC Cardioversion.

Question 5

What is the Valsalva Manoeuvre?

Answer 5

Ask the patient to blow hard against resistance, e.g. into a plastic syringe.

Question 6

What is a Carotid Sinus Massage?

Answer 6

Massage the carotid on one side gently with 2 fingers.

Question 7

How does Adenosine work in SVT?

Answer 7

It slows cardiac conduction primarily through the AV node and resets it back to sinus rhythm.

Question 8

How is Adenosine administered? (2)

Answer 8

1. Rapid IV bolus via large proximal cannula (grey cannula in antecubital fossa) (to ensure it reaches with enough impact).
2. 6mg - 12mg - 18mg.

Question 9

Cautions of Adenosine (2).

Answer 9

1. Brief Period of Asystole/Bradycardia when Injected - Impending Doom/Feeling of Death.
2. Chest Pain.

Question 10

Contraindications of Adenosine (5).

Answer 10

Give Verapamil.
1. Asthma.
2. COPD.
3. Heart Failure.
4. Heart Block.
5. Severe Hypotension.

Question 11

Management of Paroxysmal SVT - Long-Term (2).

Answer 11

1. Medication e.g. B-Blockers, CCBs, Amiodarone.
2. Radiofrequency Ablation.