supraventricular tachycardias

Question 1

what causes SVT

Answer 1

the electrical signal re-entering the atria from the ventricles

Question 2

what are the 3 main types of SVT

Answer 2

AV nodal re-entrant tachycardia
AV re-entrant tachycardia
ectopic atrial tachycardia

Question 3

describe the pathophysiology of AV nodal re-entrant tachycardia

Answer 3

re-entry circuit forms within the AVN
most common cause of SVT in patients with a structurally normal heart
more common in women

Question 4

what is the most common type of SVT in patients with a structurally normal heart

Answer 4

AV nodal re-entrant tachycardia

Question 5

describe the pathophysiology of AV re-entrant tachycardia

Answer 5

involves an accessory pathway located in the valvular rings
most common in WPW syndrome

Question 6

what is the most common SVT in wolff parkinson white syndrome

Answer 6

AV re-entrant tachycardia

Question 7

describe the pathophysiology of ectopic atrial tachycardia

Answer 7

occurs when the electrical signal originates in the atria somewhere other than the SAN

a latent pacemaker discharges action potentials at a greater frequency than the SAN so overdrive suppression is lost

Question 8

describe the clinical presentation of SVT

Answer 8

tachycardia
dyspnoea

Question 9

what are the investigations indicated in SVT

Answer 9

ECG

Question 10

what are the ECG findings in SVT

Answer 10

fast narrow complex tachycardia

QRS <0.12s

Question 11

outline the management used in ectopic atrial tachycardia

Answer 11

if ectopic beats are spontaneous and patient has a normal heart - reassurance. treatment rarely required

if symptoms are troublesome - beta blockers

advise to avoids stimulants

Question 12

outline the acute management of stable patients with SVT

Answer 12

stepwise approach

1. valsalva manoeuvre
2. carotid sinus massage
3. IV adenosine (verapamil is an alternative)
4. DCCV may be required if above fails

Question 13

describe the mechanism of action of IV adenosine in acute management of SVT

Answer 13

slows cardiac conduction through the AVN and accessory pathway if present

resets back to sinus rhythm

Question 14

what is the long term management of patients with paroxysmal SVT

Answer 14

medication
radiofrequency ablation - preferred in younger patients

Question 15

what medication can be used in the long term management of patients with paroxysmal SVT

Answer 15

beta blockers
CCBs
amiodarone