Chapter 23

Question 1

antiarrhythmic drug

Answer 1

drug used to restore normal cardiac rhythm

Question 2

arrhythmia

Answer 2

disorder of cardiac conduction and electrical impulse formation

Question 3

cinchonism

Answer 3

quinidine toxicity, which is characterized by ringing in the ears (tinnitus), dizziness, and headache

Question 4

ectopic focus

Answer 4

area of the heart from which abnormal impulses originate

Question 5

premature atrial contraction (PAC)

Answer 5

premature contraction of the atria, usually caused by an ectopic focus

Question 6

premature ventricular contraction (PVC)

Answer 6

premature contraction of the ventricles, usually caused by an ectopic focus

Question 7

proarrhythmia

Answer 7

an arrhythmia caused by administration of an antiarrhythmic drug

Question 8

supraventricular arrhythmia

Answer 8

arrhythmia that originates above the AV node in the atria

Question 9

torsade de pointes

Answer 9

a type of proarrhythmia that causes ventricular tachycardia and fainting

Question 10

ventricular fibrillation

Answer 10

the most serious arrhythmia; usually a terminal event where ventricular contractions are no longer able to effectively pump blood

Question 11

What are Arrhythmias Caused by?

Answer 11

Electrolyte disturbances

Overstimulation of the heart

Question 12

Where do arrhythmias originate?

Answer 12

Can originate anywhere in the heart

Question 13

Types of Arrhythmias (3)

Answer 13

Tachycardias
Premature contractions
Flutters and fibrillations

Question 14

Supraventricular arrhythmias

Answer 14

Originate in the atria and atrioventricular (AV) nodal areas

Include paroxysmal atrial tachycardia, atrial flutter, atrial fibrillation, and premature atrial contractions (PACs)

Question 15

Ventricular arrhythmias

Answer 15

Originate below the AV node

Include premature ventricular contractions (PVC), ventricular tachycardia, and ventricular fibrillation

Question 16

ECG monitoring

Answer 16

Arrhythmias cause abnormalities in the appearance of waves and ECG intervals.

Question 17

Electrophysiology of the Heart

Answer 17

Generated by sodium (Na+), calcium (Ca2+), and potassium (K+) ions 
Phases of cardiac action potential
Phase 0 - Generation of action potential
Phase 1–3 - Repolarization of membrane
Phase 4 - Resting level

Question 18

Electrophysiologic Properties of the Heart

Answer 18

Conduction – Na+ rapidly moves to the inside of the cell, causing reversal of the membrane potential (depolarization)

Refractoriness – K+ moves to the outside of the cell, bringing the membrane potential back to its resting level (repolarization)

Automaticity – A latent property of ventricular muscle; in pacemaker cells, there is a slow inward movement of Na+ and Ca++ and an outward movement of K+, which “automatically” excites the membrane and begins another membrane depolarization

Question 19

Therapeutic effects of Antiarrhythmic drugs

Answer 19

Influence the movement of ions

Act on a specific phase of the action potential

Can cause arrhythmia to become worse, or cause a proarrhythmia, a new arrhythmia

Question 20

Class 1 Antiarrhythmic Drugs: Sodium Channel Blockers

Answer 20

Block Na ion influx during depolarization of nerves and excitable membranes

Prolong depolarization and conduction during phase 0

Class 1A drugs prolong efflux of K ion during repolarization

Question 21

Class 1 A

Antiarrhythmic Drugs: Sodium Channel Blockers

Answer 21

Class 1A

Quinidine
Cardiac depressant, produces anticholinergic and alpha-blocking effects

Procainamide
Produces less anticholinergic and alpha-blocking actions than quinidine

Disopyramide
Produces decreased conduction and prolonged refractory period

Question 22

Class 1B

Antiarrhythmic Drugs: Sodium Channel Blockers

Answer 22

Class 1B

Lidocaine
-Prevents ventricular arrhythmias, depresses automaticity

Mexiletine - Derivative of lidocaine

Question 23

Class 1 C

Antiarrhythmic Drugs: Sodium Channel Blockers

Answer 23

Class 1C

Flecanide and propafenone
-Used to treat arrhythmias that are unresponsive to other antiarrhythmic drugs

Question 24

Class 2 Antiarrhythmic Drugs: Beta-Blockers

Answer 24

Decrease heart rate, AV conduction, and automaticity of the SA and AV nodes and of atrial and ventricular muscle

• Propranolol - Possesses beta-blocking and depressant effects
• Esmolol - Affects beta-1 receptors in the heart

Question 25

Class 3 Antiarrhythmic Drugs: Potassium Channel Blockers

Answer 25

Block potassium channels

Interfere with the efflux of K+ during repolarization Phases 1 through 3

Amiodarone
-Used for most supraventricular and ventricular arrhythmias

Sotalol
-Treats ventricular arrhythmias and atrial fibrillation

Dofetilide
-Helps in the treatment of atrial fibrillation

Ibutilide
-Indicated for the conversion of atrial flutter and atrial fibrillation to normal sinus rhythm

Question 26

Special Considerations

Answer 26

ECGs of heart patients must be constantly monitored.

Infusion rate of antiarrhythmic drug should be adjusted to its proper rate of delivery.

Awareness of the adverse effects of antiarrhythmic drugs is important.
One must be alert for their appearance.

Question 27

Preferred Therapy for Selected Arrhythmias

Answer 27

Sinus bradycardia

• Atropine
• Nonpharmacologic therapy - Cardiac pacemakers

Atrial flutter and atrial fibrillation

• Beta blockers, calcium channel blockers, and digoxin stabilize and protect the ventricles.
• Anticoagulants prevent atrial blood clots
• Electrical cardioversion helps terminate arrhythmia.

Question 28

Preferred Therapy for Selected Arrhythmias

Answer 28

Paroxysmal supraventricular tachycardia

• Acute therapy - Adenosine
• Chronic therapy
  
  • Drugs that slow AV conduction, beta-blockers, calcium channel blockers, and digoxin

Supraventricular tachycardia

• Propranolol or metoprolol
• Verapamil or diltiazem

Ventricular arrhythmias

• Acute therapy
  
  • IV administration of amiodarone or lidocaine
• Chronic therapy
  
  • Amiodarone