Supraventricular Tachycardia

Question 1

Define supraventricular tachycardia

Answer 1

Tachycardias arising from the atrium or atrioventricular junction

Question 2

What are the different types of supraventricular tachycardia?

Answer 2

AVNRT (atrioventricular nodal re-entry
tachycardia)
In some cases, AV nodal tissue contains two conduction
pathways:
• alpha (slow conduction, short refractory period)
and
• beta (fast conduction, long refractory period)
Premature atrial impulse -> anterograde conduction
through slow pathway (fast pathway is still in refractory
period) -> fast pathway recovers -> retrograde conduction
through fast pathway -> short pathway recovers due to
short refractory period -> conduction through slow
pathway -> re-entry circuit causing a fast regular heart beat

AVRT (atrioventricular re-entry
tachycardia)
This is characterised by the existence of at least one
accessory pathway between the atria and ventricles
Orthodromic: impulses travel in an anterograde
manner through AVN and in a retrograde manner
through the accessory pathway -> re-entry circuit
Antidromic: premature impulse travels in an
anterograde manner through the accessory
pathway and in a retrograde manner through the
AVN -> re-entry circuit
Wolff-Parkinson-White syndrome -> AVRT

Question 3

What are the causes/risk factors of supraventricular tachycardia?

Answer 3

• Young healthy patients with no
structural heart disease
• Hyperthyroidism
• Caffeine
• Drugs e.g. cocaine
• Alcohol
• Digoxin toxicity
• IHD
• Pericarditis
• Rheumatic heart disease
• Mitral valve prolapse
• Cardiomyopathies
• Previous cardiac surgery

Question 4

What are the symptoms of supraventricular tachycardia?

Answer 4

• Palpitations
• Dizziness
• Shortness of breath
• Syncope
• Chest pain
• Fatigue
• Sweating
• Nausea

Question 5

What are the signs of supraventricular tachycardia?

Answer 5

• Tachycardia
• Tachypnoea
• Hypotension
• Bibasal crackles (2 to heart failure)

Question 6

What investigations are carried out for supraventricular tachycardia?

Answer 6

• ECG/24hr holter
- Fast, regular, no p waves, narrow QRS complexes
- AVNRT
▪ 150-200 bpm
▪ p wave located either within or shortly after
▪ Short RP interval
- AVRT
▪ 150-250 bpm
▪ p wave after QRS complex
- WPW syndrome
▪ Short PR interval
▪ Slurred upstroke (delta wave)
• Bloods
- FBC – anaemia
- U&Es – hypokalaemia
- TFTs – hyperthyroidism
- Digoxin level
- Toxicology screen
• CXR – heart failure, pneumonia
• Echocardiogram – valvular disease, cardiomyopathy, congential/structural heart
disease
• Electrophysiologic studies

Question 7

What is the management for supraventricular tachycardia?

Answer 7

Haemodynamically unstable
• DC cardioversion

Haemodynamically stable
• Vasovagal manoeuvres e.g. Valsalva manoeuvre (blow into syringe), carotid sinus
massage
• 6mg adenosine (transient AVN blockade)
• Verapamil
• Beta-blockers e.g. metoprolol

Long-term
• Radiofrequency catheter ablation

Question 8

What are the complications of supraventricular tachycardia?

Answer 8

• Chronic heart failure
• Myocardial ischaemia/infarction
• Cardiac arrest
• Sudden death