Antiarrhythmics

Question 1

What is the obvious downside of antiarrhythmic agents?

Answer 1

They can precipitate lethal arrhythmias

But you still have to treat b/c they can be life threatening

Question 2

Cardiac arrhythmias have two basic causes:

Answer 2

Disturbances in impulse formation

Disturbances in impulse conduction

(Or both)

Question 3

Precipitating factors for cardiac arrhythmias

Answer 3

Ischemia/hypoxia

Alkalosis, electrolyte abnormalities

Excessive catecholamine exposure

Drug toxicities

Overstretching cardiac fibers

Scarred/diseased tissue

Question 4

What is the most common mechanism for arrhythmias?

Answer 4

Unidirectional block

The impulse traveling through the block is extinguished in the anterograde direction

THe conduction pathway now can re-enter in the retrograde direction —> reentry arrhythmia circuit

Question 5

What is the aim of therapy for arrhythmias?

Answer 5

Reduce ectopic pacemaker activity

Modify conduction or refractories to disable reentry

Question 6

Main mechanisms for antiarrhythmics

Answer 6

Sodium channel blockade (Class I)
Blockade of sympathetic effects (Class II)
Prolongation of the effective refractory period (Class III)
Calcium channel blockade (Class IV)

Question 7

Class IA antiarrhythmics MOA

Answer 7

Preferentially block OPEN or ACTIVATED Na+ channels

Lengthens the DURATION of action potentials

Question 8

Class IA antiarrhythmics

Answer 8

Quinidine

Procainamide

Question 9

Class IB antiarrhythmics MOA

Answer 9

Block INACTIVATED sodium channels —> shorten the duration of action potentials

Question 10

Class IB antiarrhythmics

Answer 10

Lidocaine

Question 11

Class IC antiarrhythmics MOA

Answer 11

Bind to ALL sodium channels - no effect on the duration of action potentials

Question 12

Class IC antiarrhythmics

Answer 12

Flecainide

Question 13

Class II antiarrhythmics MOA

Answer 13

Reduce adrenergic activity on the heart

BETA BLOCKERS

Question 14

Class III antiarrhythmics MOA

Answer 14

K+ channel inhibitors —> prolong the effective refractory period

Question 15

Class III antiarrhythmics

Answer 15

Amiodarone

Sotalol

Question 16

Class IV antiarrhythmics MOA

Answer 16

Calcium channel blockers —> decrease HR, contractility

Verapamil, diltiazem

Question 17

What is the secondary action of Quinidine?

Answer 17

Blocking K+ channels (prolongs the action potential duration and effective refractory period)

Question 18

Which antiarrhythmic is the “Jack of all trades”?

Answer 18

Quinidine

It was the first (that’s why it’s Class IA)

Has “Atropine-like effect”

Rarely used these days b/c we have newer drugs with fewer side effects

Question 19

What drug is used for acute or chronic treatment of supraventricular and ventricular arrhythmias?

Answer 19

Quinidine

Question 20

What is the major adverse effect of Quinidine?

Answer 20

Torsade de pointes (treat with Mg)

Question 21

Patients with _______ are at great risk of quinidine syncope/Torsade

Answer 21

Long QT

Question 22

What makes Procainamide unique from the other Class IA drug (Quinidine)?

Answer 22

IT’S a MOTHERFUCKING HIP DRUG —> SLE IN SLOW ACETYLATORS

Question 23

Lidocaine blocks ________

Answer 23

Inactivated Na+ channels —> preferentially affects damaged tissue

Question 24

DOC for acute ventricular arrhythmias

Answer 24

Lidocaine - administered IV, rapid onset

Question 25

Adverse effects of Lidocaine

Answer 25

Least toxic, least negative inotropic CONVULSIONS

Question 26

Flecainide (Tambocor) strongly blocks _______.

Answer 26

All Na+ channels —> strong pro-arrhythmic effect That’s why it’s a last-ditch effort drug for supraventricular arrhythmias and life-threatening ventricular arrhythmias

Question 27

Which specific beta blockers are Class II antiarrhythmics?

Answer 27

Propranolol (Inderal) - non-specific Acebutolol (Sectral) - B1 specific Esmolol (Breviblock) - B1 but IV only

Question 28

Which class of antiarrhythmic is Amiodarone?

Answer 28

Class III - blocks K+ channels but also has some Class I, II, and IV properties

Question 29

DOC for ventricular arrhythmias, used by ACLS

Answer 29

Amiodarone

Question 30

Effective against both supraventricular and ventricular arrhythmias

Answer 30

Amiodarone

Question 31

What are the things that make Amiodarone special?

Answer 31

NO TORSADE DE POINTES Can cause pulmonary fibrosis if used long term Gets deposited in tissues —> yellow cornea, grayishblue skin Thyroid dysfunction (iodine derivative)

Question 32

Non-selective BB used as a Class III antiarrhythmic

Answer 32

Sotalol (Betapace) Used in ventricular and supraventricular arrhythmias like amiodarone but unlike it, this one will cause TORSADE

Question 33

What are the indications for Class IV antiarrhythmics?

Answer 33

(Verapamil and Diltiazem) Reentrant supraventricular tachycardia PSVT (for long term prophylaxis) A fib and flutter ****CCBs are only effective in the atria

Question 34

DOC for acute PSVT and WPW SYndrome

Answer 34

Adenosine Enhanced K+ conductance and inhibition of cAMP-induced Ca influx (basically resets the heart) Effective only for reentry arrhythmias

Question 35

PSVT treatment order

Answer 35

ACUTE: Adenosine Esmolol CCBs (IV) CHRONIC: Beta blockers CCBs

Question 36

DOC for Torsade de pointes

Answer 36

Magnesium (mechanism unknown) Can also be used to treat seizures associated with toxemia in pregnancy

Question 37

Both hyperkalemia and hypokalemia are ________

Answer 37

Arrhythmogenic