Antiarrhythmics

Question 1

2 etiologies of arrhythmias

Answer 1

Abnormal impulse formation and alterations in impulse conduction

Question 2

Most life threatening arrhythmias

Answer 2

Ventricular tachycardia

Question 3

Class 1 antiarrhythmic drugs

Answer 3

Sodium channel blockers

Question 4

Class 2 antiarrhythmic drugs

Answer 4

Beta blockers

Question 5

Class 3 antiarrhythmic drugs

Answer 5

Potassium channel blockers

Question 6

Class 4 antiarrhythmic drugs

Answer 6

Calcium channel blockers

Question 7

Fast response fibers

Answer 7

Located in muscle–ventricle and atria

Question 8

Phase 0 of AP in fast response fibers

Answer 8

Na channels open, rapid depolarization

Class 1 drugs can slow or block phase 0

Question 9

Phase 1 of AP in fast response fibers

Answer 9

Na+ channels are inactivated

No effect of anti arrhythmic drugs

Question 10

Phase 2 of AP in fast response fibers

Answer 10

Plateau phase due to L type Ca channels
Inward Ca balanced by outward K
Class III drugs prolong plateau by blocking K channels
Class IV drugs have little effect on this type of Ca channel

Question 11

Phase 3 of AP in fast response fibers

Answer 11

Repolarization phase due to K leaving and Ca channels inactivated
Class III drugs prolong repolarization

Question 12

Phase 4 of AP in fast response fibers

Answer 12

Return to resting membrane potential
Due to Na/K pump
Digoxin can be pro-arrhythmic through blockade of phase 4

Question 13

Slow response fibers

Answer 13

SA and AV nodes
No participation of Na
Class 1 drug has no effect

Question 14

What is solely responsible for AP in slow response fibers

Answer 14

Ca

Class IV drugs block phase 0

Question 15

Prolonging action potential duration with antiarrhythmics

Answer 15

Prolongs refractoriness to pathologic stimuli and slows down rhythm

Question 16

Ischemia causes

Answer 16

Decreased O2 supply–> decreased electron transport chain–> decreased ATP–>Decreased Na/K ATPase–> Na stays in the cell keeping it depolarized causing a large amount of channels in inactive state
Requires anti-arrhythmic drug

Question 17

Class 1A drugs

Answer 17

Blocks open, activated Na channel

Question 18

Class 1B drugs

Answer 18

Blocks refractoriness–decreases rate of firing

Question 19

Class 1C drugs

Answer 19

Blocks open, activated Na channel

Question 20

Examples of 1A drugs

Answer 20

Quinidine 
Procainamide 
Pyramidine 
Moderate Na binding
Increased AP by blocking K+
Used for both ventricular and atrial dysrythmias

Question 21

Example of 1B drug

Answer 21

Lidocaine
Phenytoin
Mexiletine

Question 22

Example of 1C drug

Answer 22

Flecainide

Propafenone

Question 23

1B drugs are specific to

Answer 23

Ischemia
Used for post MI, digoxin toxicity, open heart surgery
Least Na binding; decreased AP

Question 24

1C drugs used for

Answer 24

life threatening V Tach, fibrillation and refractory SVTs
(A fib)
Strong Na binding
No effect on AP length due to no effect on K+

Question 25

FDA approved beta blockers for arrhythmias

Answer 25

Metoprolol, Propranolol, Esmolol

Question 26

Amiodarone

Answer 26

K+ channel blocker Very long half life of 20-50 days Main side effects: pulmonary fibrosis, liver toxicity, thyroid dysfunction Has 1, 2, 3, 4 properties

Question 27

Calcium channel blockers indicated for arrhythmias

Answer 27

Verapamil and diltiazem

Question 28

Side effects of calcium channel blockers

Answer 28

Decreased BP, decreased CO, lower extremity edema, constipation

Question 29

Adenosine

Answer 29

Rapidly acting AV nodal blocker--administered IV Quick half life of 30 seconds Drug of choice for paroxysmal supraventricular tachycardia

Question 30

Digoxin

Answer 30

Inhibits Na/K ATPase inhibitor

Question 31

Class 2 anti arrhythmic

Answer 31

Beta blocker Prolongs stage 4 slow depolarization by decreasing Ca depolarization Treatment of supraventricular arrythmias

Question 32

Class 3 anti arrhythmic

Answer 32

Blocks K+ channels--delays repolarization and increases AP length Can treat both atria and ventricular arrhythmias

Question 33

Sotalol

Answer 33

Class 3 anti arrythmic | Also used as beta blocker

Question 34

Dofetilide

Answer 34

Class 3 anti arrhythmic

Question 35

Ibutilide

Answer 35

Class 3 anti arrhythmic

Question 36

Class 4 anti arrhythmic

Answer 36

Non-dihydropyridine Ca channel blockers | Used for supraventricular arrhythmias especially A fib