Supraventricular Tachycardias

Question 1

What are supraventricular tachycardia (SVTs)?

Answer 1

They are are defined as arrythmias in which tachycardia originates from above or within the atrioventricular node

Question 2

What are the two main classifications of supraventricular tachycardias?

Answer 2

Focal Supraventricular Tachycardias

Re-Entry Supraventricular Tachycardias

Question 3

What are focal supraventricular tachycardias?

Answer 3

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

Question 4

What are re-entry supraventricular tachycardias?

Answer 4

They are defined as arrythmias in which electrical signals re-enter the heart, forming a self-perpetuating loop

Question 5

What are the two subclassifications of re-entry supraventricular tachycardias?

Answer 5

Atrioventricular Nodal Re-Entrant Tachycardia (AVNRT)

Atrioventricular Re-Entrant Tachycardia (AVRT)

Question 6

What is atrioventricular nodal re-entrant tachycardia (AVNRT)?

Answer 6

It is defined as an arrythmia in which the re-entry point is within the AV node

Question 7

What is atrioventricular re-entrant tachycardia (AVRT)?

Answer 7

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

Question 8

What investigation is used to diagnose supraventricular tachycardias?

Answer 8

ECG Scan

Question 9

What four ECG features indicate atrio-ventricular nodal re-entrant tachycardia (AVNRT)?

Answer 9

Tachycardia > 100bpm

Narrow QRS Complex < 120ms

Pseudo R Wave

No P Waves

Question 10

What is a pseudo R wave on ECG scans?

Answer 10

It is defined as the retrograde P wave superimposed on the QRS complex

Question 11

What three ECG features indicate atrio-ventricular re-entrant tachycardia (AVRT)?

Answer 11

Tachycardia > 100bpm

Narrow QRS Complex < 120ms

No Isoelectric Line Between The P Wave & QRS Complex

Question 12

What are the five acute management options of supraventricular tahcycardias?

Answer 12

Valsalva manoeuvre

Carotid sinus massage

Adenosine

Verapamil

Electrical cardioversion

Question 13

What are the two first line acute management options of supraventricular tachycardias?

Answer 13

Valsalva Manoeuvre

Carotid Sinus Massage

Question 14

What is the Valsalva manouevre?

Answer 14

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

Question 15

What is a carotid sinus massage?

Answer 15

It involves gently massaging the carotid artery for five seconds on one side of the neck whilst monitoring heart rhythm and blood pressure

Question 16

When is adenosine used to manage supraventricular tachycardias?

Answer 16

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

Question 17

What drug class does adenosine belong to?

Answer 17

Calcium channel blocker

Question 18

What is the mechanism of action of adenosine?

Answer 18

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

Question 19

How is adenosine administered?

Answer 19

It is administered IV via a 16G cannula in a large-calibre vein/central route

Question 20

What intial dose of adenosine is administered to manage supraventricular tahcycardias? What is the dose progression?

Answer 20

6mg

if unusccessful then

12mg

if unusccessful then

18mg

Question 21

What are the four side effects of adenosine?

Answer 21

Brief Astolye

Chest Pain

Bronchospasm

Transient Flushing

Question 22

What are the five contraindications of adenosine?

Answer 22

Asthma

COPD

Heart Failure

Heart Block

Severe Hypotension

Question 23

When is verapamil used to manage supraventricular tachycardias?

Answer 23

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

Question 24

When is electrical cardioversion used to manage supraventricular tachycardias?

Answer 24

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

Question 25

What is electrical cardioversion?

Answer 25

It involves rapidly shocking the heart back into sinus rhythm using a cardiac defibrillator machine

Question 26

What are the two chronic management options for SVTs - in order to prevent reoccurrence?

Answer 26

Pharmacological

Radiofrequency Ablation

Question 27

What are the three chronic pharmacological management options of supraventricular tachycardias?

Answer 27

Beta Blockers

Calcium Channel Blockers

Amiodarone

Question 28

What is radiofrequency ablation?

Answer 28

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

Question 29

What investigation is conducted prior to radiofrequency ablation?

Answer 29

Catheter Ablation

Question 30

What is catheter ablation?

Answer 30

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