Supraventricular tachycardia Flashcards
Define supraventricular tachycardia
Regular narrow-complex tachycardia that originates above the AV node
What are the types of supraventricular tachycardia
Focal: sinus tachy, atrial tachy, multifocal tachy
Re-entry: atrial flutter, atrial fibrillation, AVRT, AVNRT
What is the aetiology for the focal SVTs
Sinus tachycardia 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
What is the aetiology for the Re-entry SVTs
Atrial flutter: Macro-re-entrant, single large re-entry circuit around the atrium which stimulates the AV node every time it passes. (circuit fixed - rate constant)
AF: idiopathic, hyperthyroidism, pericarditis, PE, mitral stenosis
AVRT: normal AV conduction + accessory pathway - either anterograde or retrograde, orthodromic or antidromic
ANRT: re-entry circuit around the AV node
Risk factors for Supraventricular tachycardia
Nicotine Alcohol Caffeine Previous MI Digoxin toxicity/excess Paediatric congenital heart disease Cardiomyopathy Hyperthyroidism
Symptoms of Supraventricular tachycardias
Asymptomatic
Abrupt onset: Palpitations | syncope | polyuria | dyspnoea | dizziness | chest discomfort | anxiety
+ Abrupt termination
AVRT: Sensation of a regular rapid pounding in the neck
Signs of Supraventricular Tachycardia on examination
ANRT: normal, tachycardic
AVRT: Tachycardia, posible secondary cardiomyopathy (S3, RV heave, laterally displaced apex beat)
Investigations for Supraventricular Tachycardia
ECG:
AVRT: narrow complex tachycardia with no P waves, correction shows delta waves
AVNRT: Short PR interval + delta wave, secondary ST-T changes, broad QRS
TFTs: check for cause
Echo: normal, rarely see structural damage
Management for Supraventricular tachycardia
Haemodynamically unstable: DC cardioversion
- Vagal manoeuvres
- Adenosine 6mg IV
- Adenosine 12mg IV after 2mins
- Adenosine 12mg IV
- Metoprolol, amiodarone, digoxin IV OR sedate + DC cardio version
Symptomatic patients with WPW/AVNRT - catheter ablation
What is used for treatment of supraventricular tachycardia if the patient is asthmatic
Instead of adenosine use verapamil
Give examples of vagal manoeuvres and how do they work
Valsalva (straining against a closed glottis e.g. ask patient to blow into syringe)
Stick fingers down throat
Dip face in ice cold water (diving reflex)
Carotid sinus massage
Stimulation of the vagus nerve -> AV nodal conduction slows down, which may terminate the SVT
