Anti arrhythmic

Question 1

Describe the action potential graph and phases

Answer 1

Phase 0: Upstroke
- Depolarization as Na+ channels open

Phase 1: Early fast repolarization
- K+ starts going out

Phase 2: Plateau
- Na+ going in &laquo_space;K+ going out

Phase 3: Repolaristion
- Na+ channel closes and K+ still going out

Phase 4: Diastole. No movement in Na+ and K+

Question 2

What is the effective refractory period?

Answer 2

Period of time where a new action potential cannot be initiated

Question 3

What does the P wave represent?

Answer 3

Atrial contraction
- Wave of depolarization that spreads from SA node throughout atria

Question 4

What does the PR wave represent?

Answer 4

Time between the onset of atrial depolarization and the onset of ventricular depolarization.

Time taken for impulse to travel from atrium to ventricles.

Prolonged PR wave suggestive of AV block as the impulse is held at the AV node for a longer period of time.

Question 5

What does the QRS complex represent?

Answer 5

Ventricular depolarization.
R - left heart
S- right heart

Question 6

What does the QT interval represent?

Answer 6

Duration of action potential (ie. ventricular depolarization and repolarization)

Question 7

What does ST represent?

Answer 7

Ventricular repolarization

Question 8

Describe what is excitability

Answer 8

Cell can change its internal electrical balance to reach threshold

Question 9

Describe automaticity

Answer 9

Cell can generate an electrical impulse without being stimulated

Question 10

Describe conductivity

Answer 10

Cell can transfer an electrical impulse to the next cell

Question 11

List ALL the classes of antiarrhythmic drugs

Answer 11

1. Na+ channel inhibitors: Class 1A,B,C
2. Beta blockers
3. K+ channel inhibitors
4. Ca2+ channel inhibitors

Question 12

Name a Class 1A anti arrhythmic drug and its MOA

Answer 12

Procainamide
- Slows atrial depolarization
- Reduces conductivity and automaticity

Question 13

Name a Class 1B anti arrhythmic drug and its MOA

Answer 13

Lidocaine
- Slows atrial depolarization
- Shortens ventricular repolarization
- Reduces automaticity

Question 14

Name a Class 1C anti arrhythmic drug and its MOA

Answer 14

Flecainide
- Slows atrial depolarization
- Shortens ventricular repolarization

Question 15

Procainamide is a Class 1_ antiarrhythmic drug that _ ERP and action potential duration.

Answer 15

Procainamide is a Class 1A antiarrhythmic drug that increases ERP and action potential duration.

Question 16

Lidocaine is a Class 1_ antiarrhythmic drug that _ ERP and _ action potential duration.

Answer 16

Lidocaine is a Class 1B antiarrhythmic drug that does not change ERP and decreases action potential duration.

Question 17

Flecainide is a Class 1_ antiarrhythmic drug that _ ERP and action potential duration.

Answer 17

Flecainide is a Class 1C antiarrhythmic drug that has little to no effect on ERP and action potential duration.

Question 18

What is the clinical use of Flecainide?

Answer 18

Refractory ventricular tachycardias that tend to progress to VF

Question 19

List 2 beta blockers

Answer 19

Metoprolol succinate
Bisoprolol

Question 20

Describe the MOA of beta blockers

Answer 20

1. Reduce phase 4 depolarization
2. No change in ERP & APD
3. Prolonged AV conduction
4. Reduces HR and contractility (sympathetic NS)

Block beta 1 adrenergic receptors in the heart
-> reduce effects of NE and epinephrine
-> reduced HR and contractility

Question 21

What is the clinical indication for beta blockers?

Answer 21

Any condition that is primarily caused by over-activation of sympathetic nervous system.

1. Tachycardia caused by sympathetic activation
2. Atrial fibrillation

Question 22

Name a potassium channel blocker and its MOA/effect on the heart

Answer 22

Amiodarone
- Prolongs phase 3 repolarization
- Increases ERP & APD

Question 23

State the unique PK characteristic of amiodarone

Answer 23

Amiodarone is a potassium channel blocker.

It undergoes hepatic metabolism to a BIOACTIVE METABOLITE.

This means that after discontinuation, effects are maintained for 1-3 months.

Question 24

List the potassium channel blocker and its clinical indications

Answer 24

Amiodarone
- Used to MAINTAIN normal sinus rhythm in pts with AF
- Prevention of reentrant ventricular tachycardia

Question 25

List the potassium channel blocker and its adverse effect

Answer 25

Amiodarone

Symptomatic bradycardia and heart block

Question 26

List 2 non-DHP calcium channel blockers

Answer 26

Verapamil and diltiazem

Question 27

Name the non-DHP calcium channel blockers and its effects

Answer 27

Verapamil, dilitiazem

Prolongs phase 4 depolarization and reduces conductivity on AV node.

Increases ERP and APD

Question 28

What is verapamil, its uses and adverse effects?

Answer 28

It is a calcium channel blocker used for:
1. Supraventricular tachycardia (anti arrhythmia)
2. Hypertension (anti hypertensive)
3. Angina (anti anginal)

Contraindicated in pts with preexisting depressed cardiac function and hypotension

Question 29

Which 2 classes slow Phase 0 depolarization?

Answer 29

Class 1A (Procainamide) and 1C (Flecainide)

Question 30

Which class shortens phase 3 repolarization?

Answer 30

Class 1b lidocaine

Question 31

Which class suppresses phase 4 depolarization?

Answer 31

Beta blockers (metoprolol succinate and bisoprolol)

Question 32

Which class prolongs phase 3 repolarization?

Answer 32

Potassium channel blockers - amiodarone

Question 33

Which class prolongs action potential/phase 4 depolarization?

Answer 33

Verapamil and diltiazem

Non-DHP Calcium channel blockers