Supraventricular tachycardia

Question 1

Define SVT

Answer 1

A regular narrow-complex tachycardia (> 100 bpm) with
no p waves and a supraventricular origin.

AF technically counts as a type of SVT

However, SVT generally refers to:
Atrioventricular Nodal Re-entry Tachycardia (AVNRT)
Atrioventricular Re-entry Tachycardia (AVRT)

Question 2

Explain the aetiology/risk factors of SVT

Answer 2

AVNRT - A localised re-entry circuit forms around the AV node

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

Risk Factors:
Nicotine
Alcohol
Caffeine
Previous MI
Digoxin toxicity

Question 3

Summarise the epidemiology of SVT

Answer 3

VERY COMMON

2 x more common in FEMALES

Question 4

Recognise the presenting symptoms of SVT

Answer 4

May have minimal symptoms or may present with
syncope

Symptoms vary depending on rate and duration of SVT
Palpitations
Light-headedness
Abrupt onset and termination of symptoms
Other symptoms: fatigue, chest discomfort, dyspnoea, syncope

Question 5

Recognise the signs of SVT on physical examination

Answer 5

AVNRT - normal except tachycardia

Wolff-Parkinson-White - Tachycardia, Secondary cardiomyopathy (S3 gallop, RV heave, displaced apex beat)

Question 6

Identify appropriate investigations for SVT

Answer 6

ECG - Differentiating between AVNRT and AVRT once the SVT has been terminated and normal rate and rhythm are re-established:

AVNRT-appears normal
AVRT- delta-waves (slurred upstroke of the QRS complex)

24 hr ECG monitoring - will be required in patients with paroxysmal palpitations

Cardiac Enzymes - Check for features of MI (especially if there is chest pain)

Electrolytes- can cause arrhythmia
TFTs - can cause arrhythmia
Digoxin Level - for patients on digoxin

Echocardiogram - check for structural heart disease

Question 7

Generate a management plan for SVT

Answer 7

If Haemodynamically UNSTABLE - DC cardioversion

If Haemodynamically STABLE –> vagal monouevres + chemical cardioversion

Vagal manoeuvres (e.g. Valsalva, carotid massage)

Carotid massage could dislodge atherosclerotic plaques, so is only performed in young patients

If Vagal manoeuvres fail: Adenosine 6 mg bolus (can increase to 12 mg) (Contraindicated in ASTHMA as it can cause bronchospasm)

Can give verapamil 2.5-5 mg if unsuccessful/adenosine contraindicated (Alternatives: atenolol, amiodarone)

If unresponsive to chemical cardioversion or tachycardia > 250 bpm or adverse signs (low BP, heart failure, low consciousness) - Sedate and synchronised DC cardioversion/ Amiodarone

Question 8

Ongoing management of SVT?

Answer 8

AVNRT - Radiofrequency ablation of slow pathway
Beta-blockers (Alternatives: fleicanide, propafenone, verapamil)

AVRT - Radiofrequency ablation

Sinus Tachycardia - Exclude secondary cause (e.g. hyperthyroidism), Beta-blocker or rate-limiting CCB

Question 9

Identify possible complications of SVT

Answer 9

Haemodynamic collapse
DVT
Systemic embolism
Cardiac tamponade

Question 10

Summarise the prognosis for patients with SVT

Answer 10

Dependent on the presence of underlying structural heart disease

If structurally normal heart - GOOD PROGNOSIS

People with pre-excitation have a small risk of sudden death