Anti-arrythmics

Question 1

What is meant by inotropy?

Answer 1

Modification of the force of contraction

Question 2

What is meant by lusitropy?

Answer 2

Modification of the rate of relaxation (Length of Diastole)

Question 3

What is meant by Chronotropy?

Answer 3

Modification of heart rate

Question 4

What is Torsades de pointes?

Answer 4

A highly irregular form of arrhythmia

Question 5

What is an arrhythmia?

Answer 5

A condition where there are disturbances to the electrophysiology of the heart

Question 6

What are the 2 causes of arrhythmias?

Answer 6

Abnormal impulse formation
Abnormal impulse conduction

Question 7

What are the 2 types of abnormal impulse formation?

Answer 7

Triggered rhythm
Automatic rhythm

Question 8

What are the 2 types of Triggered rhythm?

Answer 8

Ectopic foci - APs arise from sites other than the SA node
Enhanced normal automaticity - More AP from SA node

Question 9

What are the 2 types of Automatic rhythm?

Answer 9

Delayed After-Depolarisations
Early After-Depolarisations (Phase 2&3)

Question 10

What are the 2 types of abnormal impulse conduction?

Answer 10

Conduction Block
Re-Entry

Question 11

What are the 3 main types of Conduction block?

Answer 11

1st degree
2nd degree
3rd degree

Question 12

What is meant by a 1st degree conduction block?

Answer 12

AV delay >0.2 ms without disrupting the hearts function

Question 13

What is meant by a 2nd degree conduction block?

Answer 13

Intermittent failure of the heart to conduct between SA and AV nodes

Question 14

What is meant by a 3rd degree conduction block?

Answer 14

Complete loss of communication between the atria and ventricles

Question 15

What are the 2 types of Re-entrant arrhythmia?

Answer 15

Circus movement
Reflection

Question 16

What is meant by circus movement?

Answer 16

Circular motion of electrical impulses in the heart leading to fluttering

Question 17

What is meant by reflection?

Answer 17

Movement of electrical impulses forwards from the atria to the ventricles, and then back down the same pathway

Question 18

What are the 6 classes of Vaughn-Williams anti-arrhythmic drugs?

Answer 18

Class 1a
Class 1b
Class 1c
Class 2
Class 3
Class 4

Question 19

What is meant by a class 1 anti-arrhythmic drug?

Answer 19

Sodium channel blocker:
a = Moderate strength
b = Weak
c = Strong

Question 20

What is meant by a class 2 anti-arrhythmic drug?

Answer 20

ß-adrenoceptor blockers

Question 21

What is meant by a class 3 anti-arrhythmic drug?

Answer 21

Potassium channel blocker

Question 22

What is meant by a class 4 anti-arrhythmic drug?

Answer 22

Calcium channel blocker

Question 23

How do class 1 (Sodium channel blockers) anti-arrhythmics work?

Answer 23

Na+ channel blockers slow the depolarisation of the myocytes, preventing contraction which occurs by opening of Na+ channels

Question 24

What are the main uses of Class 1 (Na+ channel blockers) anti-arrhythmics?

Answer 24

They can be used in life-threatening ventricular arrhythmias, ischaemic tissue and inherited long QT syndrome

Question 25

What are some examples of Class 1 (Na+ channel blockers) anti-arrhythmics?

Answer 25

Lidocaine Mexilitine

Question 26

How does lidocaine work?

Answer 26

Lidocaine is a type 1b anti-arrhythmic and a local anaesthetic It only blocks inactive or open channels, so blocks damaged, depolarised tissue It blocks during depolarisation and then rapidly dissociates

Question 27

How do Class 2 (ß-adrenoceptor blockers) anti-arrhythmics work?

Answer 27

ß1 adrenoceptors are bound to GßY and Gαs Gαs ad GTP activates adenylyl cyclase This converts AMP to cAMP cAMP increases protein kinase A levels Protein Kinase A leads to a shorter funny current ß-adrenocpetors stop this and so increase the length of the funny current

Question 28

What are the 2 types of ß-blockers?

Answer 28

Cardio selective Non-selective

Question 29

What are some examples of Cardio selective ß-blockers?

Answer 29

Atenolol Bisoprolol Carvedilol Metoprolol

Question 30

What are some examples of non-selective ß-blockers?

Answer 30

Propranolol Soltalol

Question 31

Why should asthmatics not be given non-selective ß-blockers?

Answer 31

They also act on ß2-adrenoceptors and thus can cause bronchospasm

Question 32

What are the main uses of Class 2 (ß-adrenoceptor blockers) anti-arrhythmics?

Answer 32

They can be used to manage non-sustained ventricular arrhythmias, atrial tachycardia, angina and hypertension

Question 33

What are the risks of Type 3 (K+ channel blockers) anti-arrhythmics?

Answer 33

They are extremely difficult to manage and can lead to Torsades de pointes, meaning they are only used in those who have tried other treatments

Question 34

How do Class 3 (K+ channel blockers) anti-arrhythmics work?

Answer 34

They decrease the probability of K+ influx leading to depolarisation. This increases the length of the plateau in myocytes and thus, increases the length of the refractory period

Question 35

What is an example of a Class 3 (K+ channel blocker) anti-arrhythmic?

Answer 35

Amiodarone (Also has Class 1,2 and 4 actions)

Question 36

How can some Class 3 anti-arrhythmic become pro-arrhythmic?

Answer 36

Lengthening the refractory period should prevent another action potential occurring too soon, however, some can prolong the QT interval and thus become pro-arrhythmic

Question 37

What are some main uses of amiodarone?

Answer 37

It prolongs the action potential, mainly by blocking K+ channels, this can suppress tachyarrhythmias due to re-entry and can be used in atrial fibrillation

Question 38

How do Class 4 (Ca2+ channel blockers) anti-arrhythmic drugs work?

Answer 38

They block Ca2+ influx in the pacemaker cells of the SA node This causes a delay in the depolarisation phase and extends the refractory period

Question 39

What are some examples of class 4 (Ca2+ channel blockers) anti-arrhythmic drugs

Answer 39

Verapamil Diltiazem

Question 40

What are the main uses of Class 4 anti-arrhythmics?

Answer 40

They decrease aberrant pacemakers, conduction velocity and depolarisation This blocks re-entrant rhythms such as supra ventricular tachycardia

Question 41

Where do Atrial and supra-ventricular arrhythmias occur?

Answer 41

In the Sino-Atrial or Atria-Ventricular Node

Question 42

Where do Ventricular arrhythmias occur?

Answer 42

In the common Bundle of His, bundle branches or Purkinje fibres

Question 43

What is atrial fibrillation?

Answer 43

A supra-ventricular tachyarrhythmia with uncoordinated atrial electrical activation and thus ineffective atrial contraction

Question 44

What is meant by a paroxysm?

Answer 44

A sudden attack or occurrence of symptoms

Question 45

How does Ivabradine work?

Answer 45

It blocks HCN Na+ channels and thus elongates the funny current

Question 46

How does Adenosine work?

Answer 46

It is a natural nucleoside that binds to adenosine A1 receptors It alters opening of some K+ and Ca2+ channels This slows AV nodal conduction It also hyperpolarises the cell