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Flashcards in 1 - Antiarrhythmics Deck (40):
1

What are cardiac arrhythmias caused by?

  • Disease
  • Cardiac injury
  • Drugs

2

What are arrhythmias a result from?

  • Abnormal impulse formation
  • Abnormal impulse conduction
  • Combination of both

3

What are the different types of arrhythmias?

  • Premature contractions - PVC's or PACS
  • Tachycardia 
  • Flutters - atrial flutter (300 bpm), re-entry
  • Fibrillations - uncoordinated contractions
  • Bradycardia - normal but slower
  • Heart block:
    • Complete - His purkinje system cut in half, atria & ventricles work independently
    • Partial - some more than others

4

What do antiarrhythmic medications do?

  • Depress parts of the heart that are beating abnormally

5

What are the pharmacological effects of antiarrhythmic medications?

  • Change of slope of depolarization
  • Raise threshold for depolarization
  • Alter conduction velocity in different parts of the heart

6

Where do most antiarrhythmic medications work (in which phase)?

At the effective refractory phase

7

What is the absolute (effective) refractory phase?

  • Phases 0,1,2 and most of 3 (to about -50mV)

8

What is the relative refractory period?

  • Middle of phase 3 to beginning of phase 4

9

What term is synonymous with absolute (effective) refractory period?

Depolarization

10

What are the 3 areas of the heart that have pacemaker activity?

  • SA node
  • AV node
  • Purkinje fibers

11

What drives automaticity?

Spontaneous opening and closing of K+ channels

12

What is important in determining how easily and how frequently cells can depolarize?

Threshold and resting membrane potentials

13

How does the effective refractory period (ERP) relate between packemaker area cells and mycocardial cells?

ERP in pacemaker areas is longer than myocardial cells

14

Different arrhythmias require that the ERP be _________ or _________?

Lengthened of Shortened

15

When are drugs used to induce an arrhythmia?

  • Ventricular arrhythmias due to AV node block
  • Temporary heart block until pacemaker insertion
    • Epinephrine
    • Isoproterenol - beta 1 and beta 2 agonist
    • Hypokalemic diuretics

16

What are the contraindications for antiarrhythmics?

  • Complete AV heart block
  • Congestive heart failure
  • Hypotension
  • Known hypersensitivity to the drug

17

What does the Class IA Antiarrhythmic drug's mechanism of action?

  • Na+ channel blocker (medium)
  • Blocks conduction
  • Prolongs duration of AP

18

 

What does the Class IB Antiarrhythmic drug's mechanism of action?

 

  • Na+ channel blocker (fast)
  • Blocks conduction
  • Decreases ERP
  • Shortens the AP

19

 

What does the Class IC Antiarrhythmic drug's mechanism of action?

 

  • Na+ channel blocker (slow)
  • Blocks conduction
  • Little effect on ERP
  • Slows conduction without affecting AP

20

 

What does the Class II Antiarrhythmic drug's mechanism of action?

 

  • Beta Blocker
  • Decreases SA node automaticity
  • Reduces sympathetic activity

21

 

What does the Class III Antiarrhythmic drug's mechanism of action?

 

  • K+ channel blocker
  • Prolongs the AP
  • Prolongs phase 3 repolarization

22

 

What does the Class IV Antiarrhythmic drug's mechanism of action?

 

  • Ca+ channel blocker
  • Slows conduction velocity at AV node
  • Decreases firing rate of SA and AV nodes

23

What are the 3 drugs classified as Class IA antiarrhythmics?

  • quinidine
  • procainamide (Pronestyl)
  • disopyramide (Norpace)

24

What are some characteristics of quinidine?

  • Toxic - can produce fatal arrhythmias
  • Made from bark of cinchona tree --> cinchonism
  • Site of action: atrial tissues

25

What are some characteristics of procainamide (Prnoestyl)?

  • Class IA
  • Derivative of the local anesthetic procaine
  • Reversible lupus-like syndrome in 25% of pts

26

What are some characteristics of disopyramide (Norpace)?

  • Class IA
  • Causes peripheral vasoconstriction
  • Treats ventricular arrhythmias, alternative to quinine and procainamide

27

What is the class IB drug of choice, used to treat ventricular arrhythmias?

Lidocaine (crossover drug)

28

What are other Class IB drugs that are indicated for other agents?

  • Site Ventricles:
    • phenytoin (Dilantin) - anticonvulsant
      • Gingival hyperplasia
    • mexiletine (Mexitil) - suppression of PVCs
    • tocainide (Tonocard) - suppression of life-threatening ventricular arrhythmias

29

What are the characteristics of flecainide (Tambocor) and propafenone (Rythmol)?

  • Class IC
  • Acts on ventricles
  • Approved only for use of refractory ventricular arrhythmias (life-threatening)
    • Causes arrhythmias because of profound effect on Na+ channels in healthy heart tissue -- Safety conern **

30

What class of antiarrhythmic drugs block effects of catecholamines on pacemaker cells to prolong the refractory period?

Class II

31

What do Class II antiarrhythmic drugs do?

  • Depress automaticity
  • Prolong AV conduction
  • Decrease heart rate and contractility

32

What do Class III antiarrhythmic drugs do?

  • Block K+ channels
  • Prolongs AP and prolongs effective refractory period (ERP)
  • Slows heart because drug reduces amount of norepinephrine released

33

What are some characteristics of amiodarone (Cordaron, Pacerone)?

  • Class III
  • Life-threatening recurrent ventricular fibrillation
  • Contains iodine - blue skin
  • May cause thyroid disease
  • Severe toxic effects

34

What are some characteristics of verapamil (Calan)?

  • Class IV
  • Dilates coronary and peripheral arteries

35

What is the drug of choice for cardiac arrhythmias (PSVT)?

verapamil (Calan)

36

What class IV antiarrhythmic medication is also called a cardiac glycoside?

Digoxin - used for treatment of congestive heart failure

37

What does Digoxin do?

  • Inhibits Na/K ATPase pump
  • Increases intracellular Na/Ca exchange
  • Increases intracellular Ca leading to increased contractility

38

What is used to treat bradyarrhythmias?

  • atropine (anticholinergic) - elevates sinus rate, accompany MI
  • isoproteronol (Isuprel) - beta agonist (beta1 and beta2), AV nodal block

39

What is used to treat ectopic pacemakers?

  • Postassium 
  • Magnesium ion 

40

What are the toxic reactions to antiarrhythmics?

  • Hypersensitivity
  • Hypotension, shock
  • Paradoxical arrhythmias
  • GI disorders
  • Cinchonism - quinidine