Antiarrhythmics

Question 1

What occurs at phase 4 of nodal cell action potential?

Answer 1

Spontaneous influx of Na through slow Na channels

Voltage-gated T-type Ca channels open for Ca influx

Question 2

What occurs at phase 0 of nodal cell action potential

Answer 2

Rapid depolarization

-40 mV: voltage gated L-type Ca channels open

Question 3

What occurs at phase 3 of nodal cell action potential?

Answer 3

L-type Ca channels close
K exits through voltage-gated K channels
Repolarization

Question 4

What occurs at phase 4 of cardiac myocyte action potential?

Answer 4

Constant efflux of K through rectifier channels

Resting phase at -90 mV

Question 5

What occurs at phase 0 of myocyte action potential?

Answer 5

Rapid depolarization
Voltage-gated Na channels open - rapid Na influx
Na channels inactivated
Voltage-gated L-type Ca channels open slowly for Ca influx

Question 6

What occurs at phase 1 of cardiac myocyte action potential?

Answer 6

Voltage-gated K channels open for K efflux

Question 7

What occurs at phase 2 of cardiac myocyte action potential?

Answer 7

Plateau due to balanced influx of Ca and efflux of K

Question 8

What occurs at phase 3 of the cardiac myocyte action potential?

Answer 8

Rapid repolarization
K efflux continues
L-type Ca channels gradually inactivate

Question 9

What is the MOA of class I anti arrhythmics?

Answer 9

Sodium channel blockade

Question 10

What are the class Ia antiarrhythmics?

Answer 10

Disopyramide
Quinidine
Procainamide

Question 11

What are the class Ib antiarrhythmics?

Answer 11

Lidocaine

Mexiletine

Question 12

What are the class Ic antiarrhythmics?

Answer 12

Flecainide

Propafenone

Question 13

What is the MOA of class II antiarrhythmics?

Answer 13

Beta-adrenergic channel blockade

Question 14

What are the class II antiarrhythmics?

Answer 14

Carvedilol
Esmolol
Metoprolol
Propranolol

Question 15

What is the MOA of class III antiarrhythmics?

Answer 15

Potassium channel blockade

Question 16

What are the class III antiarrhythmics?

Answer 16

Amiodarone
Dronedarone
Ibutilide
Dofetilide
Sotalol

Question 17

What is the MOA of class IV antiarrhythmics?

Answer 17

Calcium channel blockade

Question 18

What are the class IV antiarrhythmics?

Answer 18

Verapamil

Diltiazem

Question 19

What effects do class Ia antiarrhythmics have on the AP?

Answer 19

Increases threshold for depolarization at phase 0
Decreases conduction velocity
Increases the effective refractory period
Additional potassium channel blocking effects increase the AP duration

Question 20

What effects do class Ia antiarrhythmics have on the ECG?

Answer 20

Slows conduction - increases the PR interval and QRS width

Prolongs refractoriness - increases the QT interval

Question 21

What are the class effects of the class Ia antiarrhythmics?

Answer 21

Anticholinergic properties

Proarrhythmic - risk of Torsades de Pointe

Question 22

What are the specific pearls of the class Ia antiarrhythmics?

Answer 22

Disopyramide - avoid in HFrEF because it’s a negative inotrope, side effects are mainly anticholinergic in nature
Quinidine - thrombocytopenia, cinchonism, GI, rare immunologic abnormalities - only binds to open Na channels
Procainamide - ANA development, reversible drug-induced lupus, agranulocytosis, bone marrow suppression, neutropenia, thrombocytopenia

Question 23

What are the indications of the class Ia antiarrhythmics?

Answer 23

Disopyramide - ventricular and atrial arrhythmias
Quinidine - Brugada syndrome
Procainamide - unmask Brugada syndrome

Question 24

What effects do the class Ib antiarrhythmics have on action potential?

Answer 24

Shortens AP duration
Blocks Na channels that activate during late phase 2, shortening repolarization
Limited effect on phase 0

Question 25

What effects do the class Ib antiarrhythmics have on the ECG?

Answer 25

Changes will mainly be seen at faster heart rates, as there is little effect on the ECG at NSR Can shorten QTc

Question 26

What are the class effects of the class Ib antiarrhythmics?

Answer 26

Fast dissociation from Na channels Lowest potency Na channel blockers Used in ventricular arrhythmias, especially post-MI VA (tend to bind in depolarized state, which there is more of in ischemia)

Question 27

What are the pearls/side effects of the class Ib antiarrhythmics?

Answer 27

Lidocaine - NV, confusion, slurred speech, paresthesia, tremor, twitching, seizure, psychosis with toxicity. More activity in open and inactivated Na channel states. IV only Mexiletine: oral analog. NV, anorexia, paresthesia, tremor, blurred vision, dizziness, lethargy

Question 28

What is the indication of the class Ib antiarrhythmics?

Answer 28

Ventricular arrhythmias (little effect on atria tissue)

Question 29

What effects do the class Ic antiarrhythmics have on the action potential?

Answer 29

Does not change duration or refractoriness, only inhibits phase 0. Inhibits the his-purkinje conduction system

Question 30

What effects do the class Ic antiarrhythmics have on the ECG?

Answer 30

Prolongs the PR | Prolongs QRS

Question 31

What are the class effects of the class Ic antiarrhythmics?

Answer 31

Most potent Na channel blockers For supreventricular arrhythmias in structurally normal hearts Do not use in hx of MI Proarrhythmic - TdP

Question 32

What are the side effects of the class Ic antiarrhythmics?

Answer 32

Flecainide - blurred vision, dyspnea, dizziness, HA, CP, tremor, nausea, worsening HF, TdP (minor K blocking properties) Propafenone - dizziness, fatigue, taste disturbances, NV, bradycardia, worsening HF, heart block, TdP

Question 33

What are the indications for the class Ic antiarrhythmics?

Answer 33

AF conversion/maintenance "pill in the pocket" Cardioversion

Question 34

What effects do the class II antiarrhythmics have on the action potential?

Answer 34

Decreases the slope of phase 4 in cardiac pacemaker cells | Prolongs AV node repolarization