Cardiology: Arrhythmias

Question 1

What are the 4 possible rhythms in a pulseless patient?

Answer 1

1) ventricular tachycardia
2) ventricular fibrillation
3) pulseless electrical activity
4) asystole

Question 2

Cardiac arrest rhythms can be shockable or non-shockable.

Which rhythms are shockable? Which are unshockable?

Answer 2

Shockable:
- ventricular tachycardia
- ventricular fibrillation

Non-shockable:
- pulseless electrical activity
- asystole

Question 3

What is pulseless electrical activity?

Answer 3

All electrical activity except VF/VT, including sinus rhythm without a pulse.

Question 4

What is asystole?

Answer 4

When there is no significant electrical activity.

Question 5

What is a narrow complex tachycardia?

Answer 5

A fast heart rate with a QRS <0.12 seconds.

Question 6

What are the four main differentials of a narrow complex tachycardia?

What does the treatment for each focus on?

Answer 6

1) Sinus tachycardia: treatment focuses on the underlying cause

2) Supraventricular tachycardia: treated with vagal manoeuvres and adenosine

3) Atrial fibrillation: treated with rate control or rhythm control

4) Atrial flutter: treated with rate control or rhythm control, similar to atrial fibrillation

Question 7

What is a broad complex tachycardia?

Answer 7

A fast heart rate with a QRS complex >0.12 seconds.

Question 8

What are the 4 groups of broad complex tachycardia?

Answer 8

1) Ventricular tachycardia of unclear cause

2) Polymorphic ventricular tachycardia, such as torsades de pointes

3) Atrial fibrillation with bundle branch block

4) Supraventricular tachycardia with bundle branch block

Question 9

VT can be divided in monomorphic VT and polymorphic VT.

What is the difference?

Answer 9

Monomorphic: characterised by a single, stable QRS morphology with no beat-to-beat variation.

Polymorphic: has beat-to-beat variation in QRS shape and multiple QRS morphologies.

Question 10

What is monomorphic VT most commonly caused by?

Answer 10

Myocardial infarction.

Question 11

How is ventricular tachycardia of unclear cause treated?

Answer 11

IV amiodarone

Question 12

How is atrial fibrillation with bundle branch block treated?

Answer 12

Treated as AF

Question 13

How is supraventricular tachycardia with bundle branch block treated?

Answer 13

Treated as SVT

Question 14

How is polymorphic ventricular tachycardia, such as torsades de pointes treated?

Answer 14

Treated with IV magnesium.

Question 15

What is the QT interval?

Answer 15

From the start of the QRS complex to the end of the T wave.

Question 16

What is the corrected QT interval (QTc)?

Answer 16

This estimates the QT interval if the heart rate were 60 beats per minute.

Question 17

What is a prolonged QTc?

Answer 17

Men: >440 milliseconds

Women: >460 milliseconds

Question 18

What does a prolonged QT interval represent?

Answer 18

Prolonged repolarisation of the myocytes after a contraction.

Question 19

What can prolonged repolarisation result in?

Answer 19

Waiting a long time for repolarisation can result in spontaneous depolarisation in some muscle cells.

These abnormal spontaneous depolarisations before repolarisation are known as afterdepolarisations.

These afterdepolarisations spread throughout the ventricles, causing a contraction before proper repolarisation.

Question 20

What is torsades de pointes?

Answer 20

A form of polymorphic ventricular tachycardia associated with a long QT interval.

Aterdepolarisations spread throughout the ventricles, causing a contraction before proper repolarisation. This leads to recurrent contractions without normal repolarisation.

Question 21

Complications of torsades de pointes?

Answer 21

1) Will terminate spontaneously and revert to sinus rhythm

OR

2) Will progress to ventricular tachycardia (can lead to cardiac arrest)

Question 22

What are some causes of a prolonged QT?

Answer 22

1) Long QT syndrome (inherited)

2) Medications, such as antipsychotics, citalopram, flecainide, sotalol, amiodarone and macrolide antibiotics

3) Electrolyte imbalances: hypokalaemia, hypomagnesaemia and hypocalcaemia

4) Myocarditis

5) Hypothermia

6) SAH

Question 23

What medications can cause a long QT interval?

Answer 23

1) Antiarrhythmics: amiodarone, sotalol, class 1a antiarrhythmic drugs

2) Tricyclic antidepressants

3) Antipsychotics

4) Citalopram

5) Chloroquine

6) Erythromycin

Question 24

What electrolyte abnormalities can lead to a long QT interval?

Answer 24

Hypocalcaemia, hypokalaemia, hypomagnesaemia

Question 25

Management of torsades de pointes?

Answer 25

IV magnesium sulphate

Question 26

Acute management of a prolonged QT interval?

Answer 26

1) If the patient has adverse signs (systolic BP < 90 mmHg, chest pain, heart failure) --> immediate cardioversion is indicated 2) In the absence of such signs --> antiarrhythmics 3) If these fail --> electrical cardioversion may be needed with synchronised DC shocks

Question 27

General management of a prolonged QT interval?

Answer 27

1) Stopping and avoiding medications that prolong the QT interval 2) Correcting electrolyte disturbances 3) Beta blockers (not sotalol) 4) Pacemakers or implantable cardioverter defibrillators

Question 28

What antiarrythmics are indicated in prolonged QT interval?

Answer 28

1) amiodarone (ideally administered through a central line) 2) lidocaine 3) procainamide

Question 29

Who should lidocaine be used with caution in?

Answer 29

Severe left ventricular impairment

Question 30

Why are dilitazem and verapamil contraindicated in patients with ventricular tachycardia?

Answer 30

IV administration of a calcium channel blocker can precipitate cardiac arrest in such patients.

Question 31

What are ventricular ectopics?

Answer 31

Ventricular ectopics are premature ventricular beats caused by random electrical discharges outside the atria.

Question 32

Who are ventricular ectopics common in?

Answer 32

1) They are relatively common at all ages and in healthy patients 2) More common in patients with pre-existing heart conditions (e.g. IHD, HF)

Question 33

How may ventricular ectopics appear on an ECG?

Answer 33

Ventricular ectopics appear as isolated, random, abnormal, broad QRS complexes on an otherwise normal ECG.

Question 34

What is bigeminy?

Answer 34

Refers to when every other beat is a ventricular ectopic. The ECG shows a normal beat (with a P wave, QRS complex and T wave), followed immediately by an ectopic beat, then a normal beat, then an ectopic, and so on.

Question 35

Management of ventricular ectopics?

Answer 35

1) Reassurance and no treatment in otherwise healthy people with infrequent ectopics 2) Seeking specialist advice in patients with underlying heart disease, frequent or concerning symptoms (e.g., chest pain or syncope), or a family history of heart disease or sudden death 3) Beta blockers are sometimes used to manage symptoms

Question 36

What are some causes of bradycardia?

Answer 36

1) medicattions e.g. beta blockers 2) heart block 3) sick sinus syndrome 4) hypothyroidism 5) anorexia nervosa 6) raised ICP etc etc

Question 37

What is sick sinus syndrome?

Answer 37

This encompasses many conditions that cause dysfunction in the SA node.

Question 38

What is sick sinus syndrome often caused by?

Answer 38

Idiopathic degenerative fibrosis of the SA node.

Question 39

What can sick sinus syndrome result in?

Answer 39

1) sinus bradycardia 2) sinus arrhythmias 3) prolonged pauses

Question 40

There is a risk of asystole in which heart conditions?

Answer 40

1) Mobitz type 2 2) Third-degree heart block (complete heart block) 3) Previous asystole 4) Ventricular pauses longer than 3 seconds

Question 41

What does management of unstable patients and those at risk of asystole involve?

Answer 41

1) IV atropine (1st line) 2) Inotropes (e.g. isoprenaline or adrenaline) 3) Temporary cardiac pacing 4) Permanent implantable pacemaker, when available

Question 42

What are 2 options for temporary cardiac pacing?

Answer 42

1) Transcutaneous pacing, using pads on the patient’s chest 2) Transvenous pacing, using a catheter, fed through the venous system to stimulate the heart directly

Question 43

What is atropine?

Answer 43

An antimuscarinic medication and works by inhibiting the parasympathetic nervous system.

Question 44

1st line medical management of asystole (or severe bradycardia)?

Answer 44

IV atropine

Question 45

Side effects of atropine?

Answer 45

Inhibiting the parasympathetic nervous system leads to side effects of pupil dilation, dry mouth, urinary retention and constipation.