Supraventricular Tachycardia

Question 1

what are the supraventricular causes of broad complex tachycardia

Answer 1

SVT + aberrancy (BBB)
SVT + pre-excitation (activation of ventricle through different pathway)
antidromic AVRT

Question 2

def

Answer 2

an abnormally fast heart rhythm arising from improper electrical activity arising above the ventricles

Question 3

what are the four types of SVTs?

Answer 3

1 AF
2 paroxysmal SVT
3 WPW syndrome
4 atrial flutter

Question 4

aetiology

Answer 4

start from either atria or atrioventricular node
due to either:
-re-entry
-increased automaticity

1 idiopathic
2 drugs
-digoxin
-theophylline
-caffeine
-alcohol
3 COPD
4 HF
5 pneumonia

Question 5

what is the risk of theophylline

Answer 5

cause SVT

Question 6

epi

Answer 6

AF is most common followed by paroxysmal SVT

Question 7

history

Answer 7

symptoms can arise suddenly
stress, exercise, emotion can result in increased HR and rarely SVT

1 palpitations
2 SOB
3 chest pain
4 dizziness/syncope

Question 8

examination

Answer 8

1 tachycardia >150
2 tachypnoea
3 hypotension

Question 9

how does an increased HR induce symptoms of SVT

Answer 9

increased heart rate reduces filling time between each “pump”
this decreases CO and as a consequence BP

Question 10

investigations

Answer 10

1 bloods
-cardiac enzymes (if risk of MI)
-UEs (may be cause)
-FBC (anaemia may be contributing to tachycardia)
-digoxin levels
2 ECG
-short PR (<0.12s)
-narrow QRS
3 CXR
-pneumonia

Question 11

long term management of recurrent SVT

Answer 11

1 avoid triggers
2 if AVNRT
-radiofrequency ablation
-beta-blockers are first line
3 if AVRT
-patients with WPW shold be referred to cardiologist
-radiotherapy ablation
4 if sinus tachycardia
-exclude secondary causes
-beta blocker or non-dihydropyridine CCBs (diltiazem or verapamil)

Question 12

complications

Answer 12

1 HF
2 MI
3 death (with WPW syndrome)

Question 13

prognosis

Answer 13

highest risk of sudden death with pre-excitation syndrome (WPW)
highest chance of survival is with AVNRT
ablation of accessory pathway gives high chance of success

Question 14

what is cryoablation

Answer 14

SVT involving the AV node is a contraindication for radiofrequency ablation (risk of injuring AV node)
catheter with supercooled nitrous oxide gas to freeze the tissue and destroy the abnormal electrical pathways
if tissue is being frozen, then realised to be dangerous, can halt freezing and warm the tissue with no lasting consequences

Question 15

management of SVT episode

Answer 15

1 vagal manoeuvres if haemodynamically stable
-breath-holding
-carotid massage
2 IV adenosine
3 IV verapamil if adenosine fails
4 DC cardioversion as last resort

Question 16

acute management

Answer 16

PERFORM ECG ASAP
1 haemodynamically unstable
-DC cardioversion
2 haemodynamically stable
-vagal manoeuvres if haemodynamically stable regular narrow QRS tachycardia
(carotid massage, valsalva manoeuvre)
-IV adenosine if vagal manoeuvres fail
-DC cardioversion as last resort

Question 17

what are the ECG findings of AF

Answer 17

absent P wave

irregular QRS

Question 18

what are the ECG findings of atrial flutter

Answer 18

atrial rate of 300bpm giving ‘flutter waves’ or ‘sawtooth’ base line
ventricular rate often 150bpm (2:1 block)

Question 19

when should verapamil not be given in SVT

Answer 19

if patient on beta-blocker

Question 20

what does narrow and wide QRS indicate

Answer 20

narrow - SVT

wide - VT

Question 21

risk factors

Answer 21

previous MI
pneumonia
pericarditis

Question 22

when is IV adenosine contraindicated

Answer 22

severe asthma