Supraventricular Tachycardias Flashcards
What are supraventricular tachycardia (SVTs)?
They are are defined as arrythmias in which tachycardia originates from above or within the atrioventricular node
What are the two main classifications of supraventricular tachycardias?
Focal Supraventricular Tachycardias
Re-Entry Supraventricular Tachycardias
What are focal supraventricular tachycardias?
They are defined as arrythmias in which a region of the heart is more autonomic than the sinoatrial node - and takes over
This results in an organised atrial contraction, in which a wave similar to a P wave appears before the QRS complex
What are re-entry supraventricular tachycardias?
They are defined as arrythmias in which electrical signals re-enter the heart, forming a self-perpetuating loop
What are the two subclassifications of re-entry supraventricular tachycardias?
Atrioventricular Nodal Re-Entrant Tachycardia (AVNRT)
Atrioventricular Re-Entrant Tachycardia (AVRT)
What is atrioventricular nodal re-entrant tachycardia (AVNRT)?
It is defined as an arrythmia in which the re-entry point is within the AV node
What is atrioventricular re-entrant tachycardia (AVRT)?
It is is defined as an arrythmia in which the re-entry point is via an accessory pathway
This pathway allows electrical activity from the ventricles to pass to the resting atrial myocytes, creating a circuit; atria-AVN-ventricles-accessory pathway-atria
What investigation is used to diagnose supraventricular tachycardias?
ECG Scan
What four ECG features indicate atrio-ventricular nodal re-entrant tachycardia (AVNRT)?
Tachycardia > 100bpm
Narrow QRS Complex < 120ms
Pseudo R Wave
No P Waves
What is a pseudo R wave on ECG scans?
It is defined as the retrograde P wave superimposed on the QRS complex
What three ECG features indicate atrio-ventricular re-entrant tachycardia (AVRT)?
Tachycardia > 100bpm
Narrow QRS Complex < 120ms
No Isoelectric Line Between The P Wave & QRS Complex
What are the five acute management options of supraventricular tahcycardias?
Valsalva manoeuvre
Carotid sinus massage
Adenosine
Verapamil
Electrical cardioversion
What are the two first line acute management options of supraventricular tachycardias?
Valsalva Manoeuvre
Carotid Sinus Massage
What is the Valsalva manouevre?
It involves a forceful attempt of exhalation against a closed airway, usually done by closing one’s mouth and pinching one’s nose shut whilst expelling air out
What is a carotid sinus massage?
It involves gently massaging the carotid artery for five seconds on one side of the neck whilst monitoring heart rhythm and blood pressure
When is adenosine used to manage supraventricular tachycardias?
It is the second line management option of supraventricular tachycardias, in cases where individuals don’t respond to vagal manoeuvre’s and are haemodynamically stable
What drug class does adenosine belong to?
Calcium channel blocker
What is the mechanism of action of adenosine?
It works by slowing cardiac conduction through the AV node
It does this by agonistically binding to the A1 receptor in the AV node, which inhibits adenylyl cyclase thus reducing cAMP and causing hyperpolarization by increasing outward potassium flux
How is adenosine administered?
It is administered IV via a 16G cannula in a large-calibre vein/central route
What intial dose of adenosine is administered to manage supraventricular tahcycardias? What is the dose progression?
6mg
if unusccessful then
12mg
if unusccessful then
18mg
What are the four side effects of adenosine?
Brief Astolye
Chest Pain
Bronchospasm
Transient Flushing
What are the five contraindications of adenosine?
Asthma
COPD
Heart Failure
Heart Block
Severe Hypotension
When is verapamil used to manage supraventricular tachycardias?
It is the second line management option for supraventricular tachycardias, in cases where individuals don’t respond to vagal manoeuvre’s and are haemodynamically stable – however adenosine is contraindicated
When is electrical cardioversion used to manage supraventricular tachycardias?
It is the second line management option of supraventricular tachycardias, in cases where individuals don’t respond to vagal manoeuvre’s and are haemodynamically unstable
What is electrical cardioversion?
It involves rapidly shocking the heart back into sinus rhythm using a cardiac defibrillator machine
What are the two chronic management options for SVTs - in order to prevent reoccurrence?
Pharmacological
Radiofrequency Ablation
What are the three chronic pharmacological management options of supraventricular tachycardias?
Beta Blockers
Calcium Channel Blockers
Amiodarone
What is radiofrequency ablation?
It involves the application of heat to burn out the abnormal area of electrical activity. This leaves scar tissue that doesn’t transmit electrical activity
What investigation is conducted prior to radiofrequency ablation?
Catheter Ablation
What is catheter ablation?
It involves the insertion of a catheter into the femoral veins and feeding a wire through the venous system under x-ray guidance to the heart
Once in the heart it is placed against different areas to test the electrical signals at that point
