Arrhythmias

Question 1

What is an arrhythmia?

Answer 1

Abnormality in the cardiac rhythm, generated by abnormal electrical conduction usually by ectopic beats

Question 2

What are ectopic beats?

Answer 2

Conduction originating out-with the SA node

Question 3

Categories of arrhythmias

Answer 3

Tachycardias, bradicardias

SVT, AV nodal, ventricular

Question 4

Describe altered automaticity

Answer 4

Alteration (acceleration) of spontaneous cardiac rhythmicity even from on myocyte
Due to increased rate of diastolic depolarisation caused by increased sympth stimulation

Question 5

Describe triggered activity

Answer 5

After depolarisations may reach threshold potential to produce an unwarranted action potential
Due to pacing, catecholamine electrolyte imbalances, hypoxia, medications eg. digoxin

Question 6

Describe re-entry circuit

Answer 6

Fibrous ring surrounds inexcitable region of myocardium - creates bridge to allow premature, accelerated conduction to contractile myocardium
Due to congenital abnormality

Question 7

Mechanisms by which arrhythmias develop

Answer 7

Altered automaticity
Triggered activity
Re-entry circuit

Question 8

Causes of arrhythmias

Answer 8

Heart conditions (IHD, HT, valve disease, cardiomyopathy, congenital defects)
Thyrotoxicosis, electrolyte imbalance, lung disease, substance misuse

Question 9

Arrhythmia presentation

Answer 9

Palpitations, dizziness, syncope, fast/slow/irregular pulse, dyspnoea, chest pain

Question 10

Arrhythmia tests

Answer 10

ECG (exercise, 24hr)
CXR, echo
EP study - induced arrhythmia

Question 11

Arrhythmia treatment

Answer 11

Radio-frequency ablation
Cardioversion - electricity/drugs
Pacemakers

Question 12

Anti-arrhythmic drug classifications

Answer 12

Class I, II, III, IV

Question 13

AAD Class I

Answer 13

Na channel blockers (phase 0)

Slow conduction, prolong depolarisation

Question 14

AAD Class I examples

Answer 14

Disopryramide, Lignocaine, Flecainide, Propafenone

Question 15

AAD Class II

Answer 15

B-blockers (phase 4)

Slows HR

Question 16

AAD Class II examples

Answer 16

Atenolol, Propanolol

Question 17

AAD Class III

Answer 17

K channel blockers (phase 3)

Prolong repolarisation

Question 18

AAD Class III examples

Answer 18

Amiodarone, Sotalol

Question 19

AAD Class IV

Answer 19

Ca channel blockers (phase 2)

Slows HR

Question 20

AAD Class IV examples

Answer 20

Verapamil, Diltiazem

Question 21

Describe sinus bradycardia

Answer 21

Heart rate < 60, reg rhythm, QRS complexes far apart

Athletes may have it

Question 22

Causes of sinus bradycardia

Answer 22

Ischaemia/infarction of SA node
Fibrosis of atrium/SA node
Hypothermia/hypothyroidism
Drugs eg. b-blockers, verapamil

Question 23

What is fibrosis of the atrium/SA node called?

Answer 23

Sick sinus syndrome

Question 24

Sinus bradycardia treatment

Answer 24

Atropine

Pacing (perm if sick sinus)

Question 25

Describe heart block

Answer 25

AV block: block in AV/atrioventricular area | Bundle branch block: block in lower His bundle/purkinje fibres

Question 26

1st Degree heart block definition

Answer 26

Prolongation of PR interval (>0.2s)

Question 27

2nd Degree heart block definition

Answer 27

Intermittent block at the AVN (dropped beats) | Mobitz I and Mobitz II

Question 28

Mobitz I

Answer 28

Progressive PR interval prolongation, followed by dropped QRS

Question 29

Mobitz II

Answer 29

Dropped QRS but no PR prolongation Pathological Usually 2:1 or 3:1

Question 30

3rd Degree heart block

Answer 30

Complete heart block No APs from SA node get through AV node Regular rhythm - maintained by a junctional or ventricular escape rhythm P waves don’t link to QRS

Question 31

Right bundle branch block

Answer 31

Deep S waves in I + V6 | Tall R wave in V1

Question 32

Left bundle branch block

Answer 32

Deep S waves in V1 Tall R waves in I and V6 Abnormal Q waves

Question 33

Heart block treatment

Answer 33

IV atropine | Temp/perm pacing

Question 34

Where does supraventricular tachycardia arise from? What does this mean for the QRS complexes?

Answer 34

Atrium or AV junction | Therefore QRS complexes usually normal

Question 35

SVT tachycardia types

Answer 35

Atrial fibrillation | Atrial Flutter

Question 36

SVT tachycardia treatment

Answer 36

1. Vagal manoeuvres, carotid massage 2. IV adenosine 3. IV verapamil

Question 37

AF characteristics

Answer 37

Irregularly irregular - Chaotic Atrial rate >300 Absence of P waves

Question 38

3 Ps of AF

Answer 38

Paroxysmal - <48hrs Persistent - >48hrs Permanent - can't be cardioverted to NSR

Question 39

AF treatment

Answer 39

ACUTE: Cardioversion + anticoagulation Rhythm control: DC cardioversion, class I and III drugs Rate control: Digoxin + b-blocker/verapamil combo, AV node ablation Anticoagulation for prosthetic valves and CHA2DS2VASc score

Question 40

Atrial flutter characteristics

Answer 40

Atrial rate >300 Rapid re-entrant regular rhythm Saw-tooth F waves (baseline)

Question 41

Atrial flutter treatment

Answer 41

Electric cardioversion Radiofrequency ablation Class III drugs

Question 42

What is ventricular tachycardia associated with?

Answer 42

Dizziness, hypotension, cardiac arrest

Question 43

Ventricular tachycardia characteristics

Answer 43

QRS complexes are rapid, wide, and distorted The T waves are large with deflections opposite the QRS complexes Usually regular rhythm P waves are usually not visible PR interval not measurable Haemodynamically stable

Question 44

VT treatment

Answer 44

DC cardioversion if haemodynamic compromise Pulseless VT = fibrillation Amiodarone + Class I if CO and BP well maintained Calcium chloride if hyperkalaemia ICD if life-threatening

Question 45

What often follows VF

Answer 45

Cardiac arrest

Question 46

VF characteristics

Answer 46

Chaotic Irregularly irregular Shapeless, rapid oscillations with unorganised QRS complexes

Question 47

VF treatment

Answer 47

Defibrillation Magnesium chloride ICD