Arrhythmias

Question 1

Atrial fibrillation pathophysiology

Answer 1

Atria spasm (contract rapidly and irregularly)
Contraction is irregularly transmitted to ventricles giving an irregularly irregular pulse and ECG

Question 2

Prevalence of atrial fibrillation in the population

Answer 2

> 20yrs old: 3%

>80yrs old: 15%

Question 3

Clinical presentations of atrial fibrillation

Answer 3

Asymptomatic
Palpitations
Dyspnoea
Fatigue
Chest pain
Embolism (blood pools in atria = ↑risk thrombus)

Question 4

Medical treatment of atrial fibrilation

Answer 4

RATE CONTROL:
β-blockers
Na+ channel blockers
Rate limiting CCBs
Digoxin

RHYTHM CONTROL:
Amiodarone

ANTICOAGULANTS:
Warfarin
DOACs

Question 5

Atrial flutter

Answer 5

Rapid, regular atrial contraction caused by firing of an irritable automaticity focus.
Ventricular contraction is less rapid (but still rapid) due to the refractory period.
Produces “saw tooth” waves on ECG with several P waves for every QRS

Question 6

Types of supraventricular tachycardia (SVT)

Answer 6

Atrial fibrillation
Atrial flutter
Paroxysmal supraventricular tachycardia
Wolff-Parkinson-White syndrome

Question 7

Supraventricular tachycardia

Answer 7

Abnormally fast heart rhythm arising from improper electrical activity in the upper part of the heart.
Always shows a narrow QRS

Question 8

Wolff-Parkinson-White syndrome

Answer 8

Periods of tachycardia caused by an extra electrical connection between the atria and ventricles.
This connection can be congenital or develop later

Question 9

Ventricular tachycardia

Answer 9

Tachycardia caused by rapid firing of ventricular cells
↓Ventricular filling time = ↓circulating blood = medical emergency
Can lead to ventricular fibrillation
Wide QRS

Question 10

Ventricular fibrillation

Answer 10

Spasm of ventricular cells
Causes cardiac arrest
No blood circulating
Rapidly causes death

Question 11

Sinus arrest

Answer 11

A pause in heart beats caused by normal pacemaker cells in the SA node stopping firing.
The ventricles may continue to beat under other control

Question 12

Heart block definition

Answer 12

An arrhythmia where the signal from atria to ventricles is delayed or blocked

Question 13

1st degree heart block

Answer 13

Signal is delayed but still reaches ventricle

PR interval >200ms

Question 14

2nd degree heart block

Answer 14

TYPE 1:
PR interval becomes progressively longer until a beat is dropped

TYPE 2:
Dropped beats occur randomly

*The ventricles eventually do contract after a dropped beat due to firing of ventricular pacemaker cells = an escape beat

Question 15

3rd degree (complete) heart block

Answer 15

Signal is completely blocked from reaching the ventricles every time
Ventricles only contract due to escape beats at very slow rates

Question 16

Ectopic beat

Answer 16

A premature heartbeat arising from fibres outside the SA node

Question 17

Interventional treatment of atrial fibrilation

Answer 17

Ablation/MAZE procedure: destroys a faulty electrical pathway
Pacemaker

Question 18

Difference between ventricular and atrial ectopic beats

Answer 18

Atrial = narrow QRS
Ventricular = broad QRS

Question 19

Digoxin mechanism

Answer 19

Improves action of sodium-potassium pump = more Ca2+ available for contraction = increased strength of contraction

Question 20

General arrhythmia symptoms

Answer 20

Asymptomatic
Palpitations
Dyspnoea
Chest pain

(pre)syncope - extreme e.g. Vtach/Vfib

Question 21

Electrical Cardioversion

Answer 21

A controlled electric shock to restore normal rhythm

Used in Afib if chemical cardioversion (drugs) is unsuccessful.

Question 22

The Vaughan-Williams Classification

Answer 22

Divides anti-arrhythmic drugs into classes that act at different stages of the action potential

Question 23

Class I Vaughan-Williams drugs

Answer 23

Membrane stabilising agents

Block sodium channels

Question 24

Class II Vaughan-Williams drugs

Answer 24

Beta blockers

Reduce transmission of impulses in the heart’s conduction system

Question 25

Class III Vaughan-Williams drugs

Answer 25

Increase action potential duration

Question 26

Class IV Vaughan-Williams drugs

Answer 26

Calcium channel blockers

Question 27

Other (class V) Vaughan-Williams drugs

Answer 27

E.g.
Digoxin
Amiodarone
Adenosine

Question 28

Amiodarone mechanism

Answer 28

Delays repolarisation by blocking K+ channels

Question 29

Anti-coagulant therapy in cardiac arrhythmias

Answer 29

Atrial fibrillation - reduces risk of stroke by 80%

Blood pools in the atria so ↑ risk of thrombosis

Question 30

Escape beats

Answer 30

1 or 2 ectopic beats following a long pause in ventricular rhythm that prevent cardiac arrest