CVS: Anti-arrhythmics

Question 1

P wave represents the…

Answer 1

wave of depolarisation that spreads from the SA node throughout the atria

Question 2

P-R interval represents the…

Answer 2

time between the onset of atrial depolarisation and the onset of ventricular depolarisation

Question 3

QRS complex represents…

Answer 3

ventricular depolarisation

Question 4

Q-T interval represents…

Answer 4

ventricular depolarisation and repolarisation, roughly estimates the duration of an average ventricular action potential

Question 5

Class I drugs are all…

Answer 5

Na+ channel blockers.

Question 6

What is the action of class IA drugs, and what will be their effect on the ERP?

Answer 6

Slows phase 0 depolarisation.

Increases the ERP.

Question 7

What is the action of class IB drugs, and what will be their effect on the ERP?

Answer 7

Shortens phase 3 repolarisation and APD (action potential duration).

ERP unchanged.

Question 8

What is the action of class IC drugs, and what will be their effect on the ERP?

Answer 8

Slows phase 0 depolarisation.

ERP unchanged.

Question 9

Class II drugs are all…

Answer 9

B-adrenoreceptor blockers.

Question 10

What is the action of class II drugs, and what will be their effect on the ERP?

Answer 10

Suppresses phase 4 depolarisation.

ERP unchanged.

Question 11

Class III drugs are all…

Answer 11

K+ channel blockers.

Question 12

What is the action of class III drugs, and what will be their effect on the ERP?

Answer 12

Prolongs phase 3 repolarisation.

Increases ERP.

Question 13

Class IV drugs are all..

Answer 13

Ca2+ channel blockers.

Question 14

What is the action of class IV drugs, and what will be their effect on the ERP?

Answer 14

Prolongs action potential.

Increases ERP.

Question 15

A class IA drug is…

Answer 15

Procainamide.

Question 16

Effect of procainamide on 1. conduction, 2. ERP/AED, 3. automaticity?

Answer 16

1. conduction: decreases
2. ERP/AED: increases
3. automaticity: decreases

Question 17

A class IB drug is…

Answer 17

Lidocaine.

Question 18

Effect of lidocaine on 1. conduction, 2. ERP/AED, 3. automaticity?

Answer 18

1. conduction: little effect
2. ERP/AED: increases
3. automaticity: decreases

Question 19

A class IC drug is…

Answer 19

Flecainide.

Question 20

Effect of flecainide on 1. conduction, 2. ERP/AED, 3. automaticity?

Answer 20

1. conduction: suppresses phase 0 upstroke
2. ERP/AED: has a minor effect on APD and refractoriness
3. automaticity: decreases due to an increase in the threshold potential

Question 21

Clinical uses of flecainide?

Answer 21

Refractory ventricular tachycardias that tend to progress to VFib.

Question 22

Adverse effects of flecainide?

Answer 22

Increase mortality.

Question 23

A class II drug is…

Answer 23

Propanolol.

Question 24

What is the action of propanolol?

Answer 24

Diminishes phase 4 depolarisation, depressing automaticity, prolonging AV conduction, decreasing heart rate and contractility

Question 25

Uses of class II drugs?

Answer 25

1. treat tachycardias caused by increased sympathetic activity 2. for atrial flutter and fibrillation 3. AV nodal reentrant tachycardia It is the only class that reduces mortality after MI. Propanolol reduces the incidence of sudden arrhythmic death after MI.

Question 26

A class III drug is...

Answer 26

Amiodarone.

Question 27

What is the action of amiodarone?

Answer 27

1. Blockade of Ikr and Iks channels in phase III, will not affect the K+ channels in phase 0 (Ito channels). 2. Blockade of Na+ channels in phase I 3. Blockade of adrenergic receptor in phase II 4. Blockade of Ca2+ channels in phase IV

Question 28

Pharmacokinetics of amiodarone?

Answer 28

35-65% bioavailability Hepatic metabolism into bioactive desethylamiodarone Long elimination half life: 3-10 days for first t1/2, several weeks for second t1/2. Therefore, after discontinuation, effects will be maintained for 1-3 months.

Question 29

What are the clinical uses of amiodarone?

Answer 29

1. Maintaining normal sinus rhythm in Afib patients | 2. Effective in preventing recurrent ventricular tachycardia

Question 30

What is the adverse effect of amiodarone?

Answer 30

Symptomatic bradycardia and heart block

Question 31

Class IV drug are...

Answer 31

Verapamil | Adenosine

Question 32

What is the action of verapamil?

Answer 32

1. Slowing conduction 2. Prolonging APD and ERP 3. Decreasing automaticity

Question 33

What are the uses of verapamil?

Answer 33

Supraventricular tachycardia Hypertension Angina

Question 34

Adverse effects of verapamil?

Answer 34

Hypotension Contraindication: patients with preexisting depressed cardiac function

Question 35

What is the action of adenosine?

Answer 35

Suppression of AV node conduction, increases the AV nodal refractory period Stimulates cardiac K+ channel, KAch Inhibits calcium current

Question 36

What is the pharmacokinetics of adenosine?

Answer 36

Half-life in blood is <10s. Therefore, it is very useful as emergency treatment.

Question 37

What is the clinical use of adenosine?

Answer 37

Supraventricular tachycardia

Question 38

What are the adverse effects of adenosine?

Answer 38

1. Flushing 2. SOB/chest burning 3. Induction of AV block/AF 4. Headache 5. Hypotension