Supraventricular Tachycardia

Question 1

define an SVT?

Answer 1

A dysarrhythmia originating at or above the AVN with a regular, narrow complex tachycardia (QRS<120mm) at >100bpm with no p waves

Question 2

what are the 2 types of SVT?

Answer 2

Atrioventricular Nodal Re-entry Tachycardia (AVNRT)

Atrioventricular Re-entry Tachycardia (AVRT)

Question 3

outline the aetiology of AVNRT?

Answer 3

localised re-entry circuit forms around AV node-> which conducts to the ventricles faster than normal

Question 4

outline the aetiology of AVRT?

Answer 4

normal AV conductionas well as an accessory pathway

these form a re-entry circuit between atria and ventricles

Question 5

what is an accessory pathway?

Answer 5

abnormal conduction pathway

can conduct impulses towards the ventricles ( anteretrograde) or away from the ventricles ( retrograde) or in both directions

Question 6

give a classic example of AVRT? and state the re-entry pathway involved ?

Answer 6

Wolff-Parkinson- White syndrome

accessory pathway= bundle of kent

Question 7

what are the risk factors for an SVT?

Answer 7

substance misuse ( alcohol ingestion/ withdrawl, cocaine, amphetamines)

digoxin toxicity

Previous cardiac surgery to correct congenital heart defects-> Cardiac surgery leaves scar tissue in the myocardium, which provides a substrate for re-entry pathways

Question 8

summarise the epidemiology of SVT?

Answer 8

VERY COMMON

2 x more common in FEMALES

Question 9

What are the presenting symptoms of SVT?

Answer 9

Palpitations

Light-headedness

Polyuria (due to increased atrial pressure causing ANP release)

Abrupt onset and termination of symptoms

fatigue, chest discomfort, dyspnoea, syncope, N+V

Question 10

what are the signs of SVT on physical examination?

Answer 10

AVNRT - normal except tachycardia

Wolff-Parkinson-White

• Tachycardia
• Secondary cardiomyopathy (S3 gallop, RV heave, displaced apex beat)

Question 11

what are the investigations for svt?

Answer 11

ECG

24 hr ECG monitoring- needed in patients with paroxysmal

cardiac enzymes-> check for MI features

Electrolytes - can cause arrhythmia (hypokalaemia)

Toxicology screen – when drug abuse is suspected

TFTs - can cause arrhythmia

Digoxin Level - for patients on digoxin

Echocardiogram - check for structural heart disease

Question 12

what are the possible complications of SVT?

Answer 12

Haemodynamic collapse

DVT

Systemic embolism

Cardiac tamponade

Question 13

describe ECG for SVT?

Answer 13

Narrow complex tachycardia

shortened PR interval

p waves buried in QRS

Question 14

How can AVRT and AVNRT be differentiated?

Answer 14

acutely, AVRT and AVNRT cannot be differentiated on ECG, as they both appear as narrow complex tachycardia

Only after correcting the tachycardia, you see delta wave in AVRT but no wave in AVNRT.

Question 15

outline the management plan for SVT?

Answer 15

Question 16

What are vagal maneouvres?

Answer 16

VAGAL manoeuvres(e.g. Valsalva, carotid massage)

Carotid massage could dislodge atherosclerotic plaques,so is only performed in young patients

Valsava manoeuvres inc straining against closed glottis to stim vagus nerve so slow down heart rate - can also stick fingers down throat, press hard on eyeballs, dip face in cold water, drink cold water or swallow crushed ice.

Question 17

summarise the prognosis of patients with SVT?

Answer 17