Antidysrythmic Drugs

Question 1

What is atrial fibrilation?

Answer 1

a chaotic rhythm of the QRS complexes

Question 2

What is shown here?

Answer 2

an illustration of a damaged pathway

Question 3

What is shown here?

Answer 3

Depolarization struggles to get through the muscle, but does, the P-QRS complex is just bigger

Question 4

What is shown here?

Answer 4

re-entry

Question 5

What is shown here?

Answer 5

Depolarization struggles to get around, but keeps going around in circles: re-entry arrhythmias

Question 6

What do class I antidysrhythmic drugs do?

Answer 6

block voltage-sensitive Na channels

Question 7

What do class II antidysrhythmic drugs do?

Answer 7

beta adrenoceptor antagonists (beta blockers)

Question 8

What do class III antidysrhythmic drugs do?

Answer 8

They prolong the refractory period of the myocardium - increase the refractory period gap

Question 9

What do class IV antidysrhythmic drugs do?

Answer 9

Calcium antagonists - impair impulse propagation in damaged areas of the myocardium and dilate coronary arteries

Question 10

How do class I antidysrhythmic drugs work?

Answer 10

they block Na channels in the open or refractory stage (in depolarized/damaged muscle) and inhibit the refractory stage

Question 11

When do class I antidysrhythmic drugs have the greatest efficacy?

Answer 11

when the heart is beating rapidly

Question 12

What drug is a class Ib antidysrhythmic drug?

Answer 12

lidocaine

Question 13

Class Ib antidysrhythmic drugs _______ and _______ rapidly.

Answer 13

associate, dissociate

Question 14

What are class Ib antidysrhythmic drugs useful for?

Answer 14

the control of ventricular dysrhythmias after myocardial infarction

Question 15

What drug is a class Ic antidysrhythmic drug?

Answer 15

flecainide

Question 16

Class Ic associate and dissociate more ____.

Answer 16

slowly

Question 17

Since class Ic drugs associate and dissociate more slowly what does that say about their steady state block level?

Answer 17

it does not vary with the stage of the cycle

Question 18

What are class Ic drugs used for?

Answer 18

general reduction in excitation and have less effect against premature beats like class Ib

Question 19

What will class Ic drugs suppress?

Answer 19

re-entrant rhythms

Question 20

What drugs are class 1a antidysrhythmic drugs?

Answer 20

Procainamide and Quinidine

Question 21

How do muscarinic receptors affect the heart?

Answer 21

they decrease heart rate and excitability

Question 22

What drug is a class II antidysrhythmic drug?

Answer 22

propanolol - beta antagonist

Question 23

What are class II antidysrhythmic drugs used to do?

Answer 23

reduce excitability due to sympathetic over-activity and reduce AV conduction in atrial tachycardias to slow ventricular rate

Question 24

Why would you want to use propranolol in cats with thyroid hyperplasia?

Answer 24

because thyroid hyperplasia can cause arythmias

Question 25

What is the main class III antidysrhythmic drug?

Answer 25

amiodarone

Question 26

What is the special feature of class III antidysrhythmic effects?

Answer 26

they prolong the cardiac action potential and increase refractory period

Question 27

What effects does Class III antidysrhythmic drugs have?

Answer 27

it produces ventricular and supra-ventricular antidysrhythmic effects - complex mechanism including K channel block and calcium channel block

Question 28

What are the main examples of class IV antidysrhythmic drugs?

Answer 28

Verapamil and diltiazem

Question 29

What do class IV antidysrhythmic drugs do?

Answer 29

they block sensitive Ca channels which inhibits transient inward current and thus suppressing premature ectopic beats and re-entrant rhythms

Question 30

What do class IV antidysrhythmic drugs do to the plateau phase of the action potential?

Answer 30

it is shortened

Question 31

What is the effect of Class IV antidysrhythmic drugs on the coronary arteries?

Answer 31

it dilates them

Question 32

What is procainamide?

Answer 32

a class 1a antidysrhythmic drug

Question 33

When is procainamide indicated?

Answer 33

in dogs for maintenance of ventricular arrhythmias or ventricular tachycardia In humans - Torsades de points

Question 34

When is Procainamide contraindicated?

Answer 34

in dogs with conduction block

Question 35

When is lidoocain used?

Answer 35

without epinephrine intravenously for severe acute ventricular arrhythmias of any cause

Question 36

Why isn't lidocaine given orall?

Answer 36

because of the efficient first pass effect through the liver

Question 37

When should you reduce doses of lidocaine?

Answer 37

in congestive heart failure or hepatic disease

Question 38

What does propranolol prevent?

Answer 38

reflex tachycardia

Question 39

What does propranolol reduce?

Answer 39

blood pressure and ventricular hypertrophy in cardiomyopathy associated with hyperthyroidism

Question 40

What is a possible side effect of propanolol use?

Answer 40

bronchial muscle spasm

Question 41

What does amiodarone do?

Answer 41

prolongs the refractory period of cardiac action potential

Question 42

What amiodarone used for?

Answer 42

treatment of supra-ventricular and ventricular arrhythmias

Question 43

What side effects are associated with amiodarone?

Answer 43

pulmonary fibrosis, gastro-intestinal disturbances, corneal deposits

Question 44

What is the half-life with amiodarone?

Answer 44

long elimination half-life

Question 45

What type of drugs are Verapamil and Diltiazem?

Answer 45

class IV antidysrhythmic

Question 46

How do Verapamil and Diltiazem work?

Answer 46

they inhibit slow Ca channels and dilate capillaries

Question 47

What conditions are Verapamil and Diltiazem favored for?

Answer 47

supraventricular tachycardias

Question 48

How is Verapamil favored to be given?

Answer 48

IV

Question 49

How is Diltiazem favored to be given?

Answer 49

long-term oral administration