Tachyarrhythmias

Question 1

Definition of narrow complex tachycardia?

Answer 1

Rate >100bpm
QRS complex <120ms
- narrow QRS complxes maen that the ventricles are being depolarised by normal conduction pathway

Question 2

Causes of regular narrow complex tachycardia

Answer 2

Sinus tachycardia
Focal atrial tachycardia
Atrial flutter
Atrioventricular re-entry tachycardia e.g. WPW syndrome
Atrioventricular nodal re-entry tachycardia (SVT)

Question 3

What are the causes of sinus tachycardia

Answer 3

Infection
Pain
Anxiety
Exercise
Bleeding
Dehydration 
Sepsis - due to systemic vasodilation (to keep BP up)
Drugs - caffeine, nicotine, salbutamol
Anaemia
Pregnancy 
CO2 retention 
Autonomic neuropathy 
Fever
Pulmonary embolism
Hypertyroidism

Question 4

What is focal atrial tachycardia + ECG changes

Answer 4

A group of atrial cells acting as the pacemaker, and out-pacing the sinoatrial node >150bpm
P wave becomes superimposed onto the preceding T-wave

Question 5

What is atrial flutter

Answer 5

Rate >250bpm in the atria, leading to a saw-tooth baseline
- ?P waves can’t be seen
AV node passes on some of the impulses, so the ventricular rate is a multiple of the atria rate
- e.g. atria 300bpm = 100bpm (3:1 AV block)`

Question 6

What is atrioventricular re-entry tachycardia

Answer 6

An accessory pathway that allows electrical activity from the ventricles to pass to the resting atrial monocytes, creating a circuit
e.g. Wolff-Parkinson-White syndrome

Question 7

What is atrioventricular nodal re-entry tachycardia + ECG signs

Answer 7

New circuits form within the AV node, which constantly stimulate the ventricles to contact
- causes p waves to be very close to the QRS/not visible

Question 8

What are the irregular narrow-complex tachycardias

Answer 8

Sinus arrhythmia
Atrial fibrillation
Atrial flutter with variable block
Multi-focal atrial tachycardia

Question 9

What is a sinus arrhythmia

Answer 9

A normal variant - rate changes on inspiration and expiration
- sinus tachycardia + ectopic beats

Question 10

What is multi-focal atrial tachycardia

Answer 10

Like focal atrial tachycardia, but with multiple groups of cells taking it in turns to initiate cardiac cycle
- associated with COPD

Question 11

How are narrow-complex tachyarrhythmias managed

Answer 11

Oxygen, 12-lead ECG and IV access
No adverse signs
- if irregular rhythm; probably AF
- regular rhythm; by definition is an SVT, and vagal manoeuvres should be attempted
- adenosine if this doesn’t work
- bet-blockers for possible atrial flutter if this fails
Adverse signs
- get help
- sedation and DC cardioversion (up to 3)
- correct electrolytes
- amiodarone and repeat shock as needed

Question 12

Describe the use of adenosine in SVT

Answer 12

6mg bolus IV with 0.9% saline flush while recording a 12-lead rhythm strip
12mg bolus IV after 2 mins if initial dose unsuccessful
Max one more 12mg dose before attempting verapamil

Question 13

What are the side effects of adenosine?

Answer 13

Chest tightness
Dyspnoea
Headache
Flushing

Question 14

Contraindications of adenosine

Answer 14

Asthma
2nd/3rd degree heart block
Sinoatrial disease

Question 15

Definition of broad-complex tachycardia?

Answer 15

Heart rate >100bpm
QRS >120ms
- no clear QRS complexes indicates VF or asystole

Question 16

Possible causes of a broad-complex tachycardia

Answer 16

Ventricular fibrillation
Ventricular tachycardia
Any cause of narrow-complex tachycardia + BBB/metabolic causes of a wide QRS
Antidromic AVRT

Question 17

Describe ventricular fibrillation + ECG

Answer 17

Ventricles attempt to contract at rates up to 500bpm, this leads to a loss of cardiac output
Chaotic and no discernible pattern on ECG

Question 18

Describe ventricular tachycardia + ECG

Answer 18

Foci in ventricles discharge at a high frequency, causing an abnormal spread or charge through the ventricles = wide and abnormal QRS
Broad and regular QRS complex and no P waves

Question 19

What is Torsade de pointes

Answer 19

Polymorphic ventricular tachycardia - VT with a varying axis

- looks like ventricular fibrillation

Question 20

What in the history and examination could help you differentiate an SVT + BBB and VT?

Answer 20

Recent MI - most likely VT as it can cause ventricular damage
12-lead ECG
Response to certain medications

Question 21

What ECG findings suggest a patient is experiencing VT, not SVT + BBB?

Answer 21

Positive or negative QRS concordance in all leads
QRS >160ms
Marked left axis deviation
AV dissociated (p waves are independent of the QRS complexes)
Fusion or capture beats
RSR’ pattern - where R is taller than R’

Question 22

How is a broad-complex tachycardia managed?

Answer 22

Oxygen, 12-lead ECG and IV access
No adverse signs
- correct electrolyte abnormalities
- give amiodarone if rhythm is regular (adenosine instead if known history of SVT + BBB)
- seek expert help and give IV magnesium
- if none of this is successful; sedation and shock is required
Averse signs
- sedation and DC cardioversion (up to 3)
- correct electrolytes
- amiodarone and further cardioversion as needed

Question 23

How should the patient be managed once the VT is corrected?

Answer 23

Establish the cause
Maintain anti-arrhythmics (if MI was the cause) for 12-24 hours
- solatol or amiodarone
ICD or surgical isolation of arryhythmic area if required

Question 24

Why does VF require a non-synchronised DC shock?

Answer 24

Synchronised shocks use the R wave to trigger defibrillation - and VF doesn’t have an R waves

Question 25

What are the adverse signs in a broad complex tachycardia?

Answer 25

Low cardiac output - clammy, low blood pressure, decreasing consciousness
Oliguria
Angina
Pulmonary oedema

Question 26

What are the adverse signs in a narrow complex tachycardia?

Answer 26

Shock
Chest pain/ischaemia
Heart failure
Syncope