Cardiology - Arrhythmias

Question 1

In a pulseless patient what rhythms are shockable or non-shockable?

Answer 1

Shockable
Ventricular tachycardia
Ventricular fibrillation

Non-shockable
Pulseless electrical activity
Asystole

Question 2

What are narrow and broad complex tachycardias?

Answer 2

Narrow
Fast heart rate with QRS less than 0.12 seconds

Broad
Fast heart rate with QRS longer than 0.12 seconds

Question 3

What are the 4 main differentials of narrow complex tachycardia?

Answer 3

Sinus tachycardia
Supraventricular tachycardia (treat with vagal manoeuvres and adenosine)
Atrial fibrillation (rate control or rhythm control)
Atrial flutter (rate control or rhythm control)

Question 4

How should patients with narrow complex tachycardia with life-threatening features be treated?

Answer 4

Synchronised DC cardioversion under sedation or general anaesthesia

IV amiodarone added if DC shocks unsuccessful

Question 5

What are the different types of broad complex tachycardia?

Answer 5

Ventricular tachycardia (IV amiodarone)
Polymorphic ventricular tachycardia e.g. torsades de pointes (IV magnesium)
Atrial fibrillation with bundle branch block (treated as AF)
Supraventricular tachycardia with bundle branch block (treated as SVT)

Question 6

How should patients with life-threatening broad complex tachycardia be treated?

Answer 6

Synchronised DC cardioversion under sedation or general anaesthesia

IV amiodarone if shocks don’t work

Question 7

What causes atrial flutter?

Answer 7

Re-entrant rhythm

Electrical signal re-circulates in self-perpetuating loop

Question 8

What is a 2:1 conduction in atrial flutter?

Answer 8

Signal does not enter ventricles every time due to long refractory period of AVN

So two atrial contractions for every one ventricular contraction (2:1)

300 beats per minute so 150 beats per minute in the ventricles

Question 9

How does atrial flutter appear on ECG?

Answer 9

Sawtooth appearance

Repeated P wave at 300 bpm
Narrow complex tachycardia

Question 10

How is atrial flutter treated?

Answer 10

Anticoagulation based of CHADSVASc score
Radiofrequency ablation of re-entrant rhythm

Question 11

When is a QT interval prolonged?

Answer 11

Men > 440ms
Women > 460ms

Question 12

What does a prolonged QT interval actually mean?

Answer 12

Prolonged repolarisation of myocytes after contraction

Long repolarisation can cause spontaneous depolarisation in some muscle cells- afterdepolarisations

Afterdepolarisations spread throughout ventricles causing contraction before proper repolarisation

When this leads to recurrent contractions without normal repolarisation - torsades de pointes

Question 13

How do you identify Torsades de pointes vs ventricular tachycardia?

Answer 13

QRS complexes get progressively smaller then bigger whereas ventricular tachycardia QRS stays about the same

Question 14

What causes prolonged QT?

Answer 14

Long QT syndrome
Medications- antipsychotics, citalopram, flecainide, sotalol, amiodarone, macrolides
Hypokalaemia
Hypocalcaemia
Hypomagnesaemia

Question 15

How do you manage a prolonged QT interval?

Answer 15

Stop and avoid medications which prolong QT interval
Correct electrolytes
Beta blockers (not sotalol)
Pacemakers or ICDs

Question 16

What is the acute management of torsades de pointes?

Answer 16

Correct underlying cause
Magnesium infusion
Defibrillation if VT occurs

Question 17

What are ventricular ectopics?

Answer 17

Premature ventricular beats caused by ventricular foci

Question 18

How do patients present with ventricular ectopics?

Answer 18

Random extra or missed beats

Any age and in healthy patients

More common in patients with pre-existing heart conditions

Question 19

How do ventricular ectopics appear on ECG?

Answer 19

Random
Broad QRS complexes
Otherwise normal

Question 20

What is bigeminy?

Answer 20

Every other beat is a ventricular ectopic

Question 21

How are ventricular ectopics treated?

Answer 21

Reassurance
Beta blockers if symptomatic

Question 22

Outline heart block

Answer 22

First-degree
- Prolonged PR interval (over 5 squares)
- P wave always followed by QRS

Second degree Mobitz 1 (Wenckebach phenomenon)
- PR interval progressively gets longer until QRS not fired then it resets

Second degree Mobitz 2
- Intermittent failure through AVN
- Random absence of QRS complexes after P waves
- Risk of progression to complete heart block
- Usually set ratio e.g. 3:1 block

Third-degree heart block
- No relationship between P waves and QRS complexes
- High risk of progression to asystole

Question 23

What can cause bradycardia?

Answer 23

Medications e.g. beta blockers
Heart block
Sick sinus syndrome

Question 24

What is sick sinus syndrome?

Answer 24

Encompasses many conditions that cause dysfunction in SAN

Caused by idiopathic degenerative fibrosis of the SAN

Question 25

What can sick sinus syndrome lead to?

Answer 25

Sinus bradycardia
Sinus arrhythmias
Prolonged pauses

Question 26

When is there a risk of asystole?

Answer 26

Mobitz type 2
Third degree heart block
Previous asystole
Ventricular pauses over 3 seconds

Question 27

How are unstable patients and those at risk of asystole managed?

Answer 27

IV atropine
Inotropes (isoprenaline or adrenaline)
Temporary cardiac pacing
Permanent implantable pacemaker

Question 28

What options for temporary cardiac pacing are there?

Answer 28

Transcutaneous pacing (pads on patient’s chest)
Transvenous pacing
(catheter fed through venous system to directly stimulate heart)