Supraventricular Tachycardia Flashcards
Define Supraventricular Tachycardia (SVT)?
A regular narrow-complex tachycardia (> 100 bpm) with no p waves and a supraventricular origin
What does SVT generally refer to?
AF technically counts as a type of SVT
However, SVT generally refers to:
- Atrioventricular Nodal Re-entry Tachycardia (AVNRT)
- Atrioventricular Re-entry Tachycardia (AVRT)
What is the Aetiology of AVRNT?
A localised re-entry circuit forms around the AV node
What is the aetiology of AVRT?
A re-entry circuit forms between the atria and ventricles due to the presence of an accessory pathway (Bundle of Kent)
What are the risk factors for SVT?
Nicotine Alcohol Caffeine Previous MI Digoxin Toxicity
What is the epidemiology of SVT?
Very Common
2x more common in Females
What are the presenting symptoms of SVT?
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
What are some of the rarer symptoms of SVT?
Fatigue
Chest discomfort
Dyspnoea
Syncope
What are the signs of AVNRT on physical examination?
Normal except tachycardia
What are the signs of Wolff-Parkinson-White on physical examination?
Tachycardia Secondary Cardiomyopathy (S3 gallop, RV heave, displaced apex beat)
What investigations do we do for SVT?
ECG Cardiac Enzymes Electrolytes TFTs Digoxin Level Echocardiogram
Why do we do an ECG for SVT?
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)
24hr ECG monitoring - will be required in patients with paroxysmal palpitations
Why do we do Cardiac Enzymes for SVT?
Check for features of MI (especially if there is chest pain)
Why do we do Electrolytes tests for SVT?
Can cause arrhythmia
Why do we do TFTs for SVT?
Can cause arrhythmia
Why do we do Digoxin Level for SVT?
For patients on digoxin
Why do we do an Echocardiogram for SVT?
Check for structural heart disease
What is the management plan for SVT if haemodynamically unstable?
DC cardioversion
What is the management plan for SVT if haemodynamiccaly stable?
Vagal Manoeuvres + Chemical cardioversion
What are some Vagal Manoeuvres?
e.g. Valsalva, Carotid massage
Why are Carotid Massage only performed in young patients?
Could dislodge atherosclerotic plaques
What do we do if vagal manoeuvres fail?
Adenosine 6 mg bolus (can increase to 12 mg)
Can give verapamil 2.5-5mg if unsuccessful/adenosine contraindicated due to asthma
Alternatives: atenolol, amiodarone
When is Adenosine contraindicated?
In asthma as it can cause bronchospasm
What do you have to do if a patient with SVT is unresponsive to chemical cardioversio or tachycardia > 250bpm or adverse signs (low BP, heart failure, low consciousness)?
Sedate and synchronised DC cardioversion
Amiodarone
What is the ongoing management of AVNRT?
Radiofrequency ablation of slow pathway
Beta-blockers
Alternatives: fleicanide, propafenone, verapamil
What is the ongoing management of AVRT?
Radiofrequency ablation
What is the ongoing management plan of Sinus Tachycardia?
Exclude secondary cause (e.g. hyperthyroidism)
Beta-blocker or rate-limiting CCB
What are the possible complications of SVT?
Haemodynamic collapse
DVT
Systemic Embolism
Cardiac Tamponade
