Antiarrhythmic Agents

Question 1

What are the 5 phases of the Action Potential of the Cardiac Muscle Cell?

Answer 1

Phase 0: Sodium ions move INTO cells (depolarization)
Phase 1: Potassium ions move OUT of cells
Phase 2: Calcium ions move INTO cells (plateau stage)
Phase 3: MORE Potassium ions move OUT of cells (repolarization)
Phase 4: Back at rest and ready to start again

Summit Sodium (DEpolarization)
Plummet Potassium (REpolarization)

Question 2

What are some causes of Cardiac Arrhythmias?

Answer 2

• Electrolyte imbalances that alter the action potential
• Decrease in oxygen delivered to the cells
• Structural damage that changes the conduction pathway through the heart
• Acidosis or accumulation of waste products that alter the action potential
• Drugs that alter the action potential or cardiac conduction

Question 3

How do the classifications of Antiarrhythmics work?

Answer 3

Class I: Block sodium channels
Class II: Act on autonomic receptors
Class III: Block potassium channels
Class IV: Block calcium channels

Question 4

Lifespan considerations of Antiarrhythmics
In Children

Answer 4

• More likely to experience Adverse effects
• Digoxin IS approved in children
• Doses are calculated by age and weight
• Ablation procedures can be successful as alternative to drug therapy

Question 5

Lifespan considerations of Antiarrhythmics
In Adults

Answer 5

• Used frequently during emergencies
• Monitor frequently
• Avoid use in pregnancy and lactation (alternative feeding method needed)

Question 6

Lifespan considerations of Antiarrhythmics
In Older Adults

Answer 6

• Frequently prescribed
• More likely to experience adverse effects
• Start low

Question 7

Class I Antiarrhythmics
Sub-Classes and Drug Names

Answer 7

• Ia: Procainamide, quinidine
• Ib: Lidocaine
• Ic: Flecainide, propafenone

Question 8

Class I Antiarrhythmics
Mechanism of Action

Answer 8

• Block the sodium channels in the cell membrane during Phase 0 of the action potential
• Decreases depolarization
• Decreases automaticity of ventricular cells
• Increases ventricular fibrillation threshold

Question 9

Class I Antiarrhythmics
Indications

Answer 9

• Tachycardia
• Life-threatening ventricular arrythmias
• Symptomatic paroxysmal atrial arrhythmias

Question 10

Class I Antiarrhythmics
Contraindications

Answer 10

Absolute:
* Allergy
* Bradycardia, heart block
* CHF
* Hypotension, shock
* Electrolyte disturbances

Cautions:
* Renal or hepatic dysfunction
* Pregnancy or lactation

Question 11

Class I Antiarrhythmics
Adverse Effects

Answer 11

Due to delayed action potential of all cells
* CNS: dizziness, fatigue, slurred speech
* GI: Nausea and vomiting
* CV: Arrhythmias, heart block, hypotension, vasodilation, cardiac arrest
* Respiratory depression
* Misc.: rash, loss of hair, potential bone marrow suppression

Procainamide: fever, hepatomegaly, neutropenia, painful joints, liver failure, pericarditis, hemolytic anemia

Question 12

Class I Antiarrhythmics
Drug Interactions

Answer 12

Numerous
ie. Cemetidine, Digoxin, warfarin

Food:
Quinidine: foods that alkanalize the urine (citrus juice, vegetables, antacids, milik products); grapefruit juice

Question 13

Class II Antiarrhythmics
Mechanism of Action

Answer 13

• “-olol”s: Beta-adrenergic blockers block beta receptors, causing a depression of Phase 4 of the action potential (rest phase)
• Digoxin and Adenosine act on the autonomic nervous system
• Competitively block beta receptors in the heart and kidneys
• Decrease HR, cardiac excitability, and cardiac output
• Slow conduction through the AV node

Question 14

Class II Antiarrhythmics
Indications

Answer 14

• Rapid atrial fibrillation
• Atrial flutter
• Paroxysmal SVT
• PVCs
• Ventricular tachycardia

Adenosine is used for SVT when other measures are not effective - it is quick acting and short lasting

Question 15

Class II Antiarrhythmics
Drug Names

Answer 15

Acebutolol
Esmolol
Propranolol

Digoxin
Adenosine

Question 16

Class II Antiarrhythmics
Contraindications

Answer 16

Absolute:
* Allergy
* Sinus bradycardia
* AV block
* Cardiogenic shock
* Respiratory Depression

Caution:
* Diabetes
* Thyroid dysfunction
* Asthma or COPD
* Pregnancy and lactation
* Renal and hepatic dysfunction

Question 17

Class II Antiarrhythmics
Adverse Effects

Answer 17

• CNS: Dizziness, insomnia, dreams, fatigue
• CV: hypotension, bradycardia, AV block, arrhythmias
• Respiratory: Bronchospasm, dyspnea
• GI: Nausea, vomiting, anorexia

Question 18

Class II Antiarrhythmics
Drug Interactions

Answer 18

• Verapamil or diltiazem (increased risk of CV effects)
• Antidiabetic medications
• Methylxanthines

Question 19

Class III Antiarrhythmics
Mechanism of Action

Answer 19

• Block potassium channels and slow outward movement of potassium during Phase 3 of the action potential (prolonging it)

Question 20

Class III Antiarrhythmics
Indications

Answer 20

• Life-threatening ventricular arrhythmias
• Maintenance of sinus rhythm after conversion of atrial arrhythmias

Question 21

Class III Antiarrhythmics
Contraindications

Answer 21

Absolute:
* When used for life threatening arrhythmias - there is NO contraindication
* When used for NON-life threatening arrhythmias: bradyarrhythmias

Cautions:
* Shock, hypotension
* Respiratory depression
* Prolonged QT interval
* Renal or hepatic disease
* Amiodarone: thyroid or pulmonary disease

Question 22

Class III Antiarrhythmics
Drug Names

Answer 22

Sotalol
Amiodarone
Dofetilide
(SAD)

Question 23

Class III Antiarrhythmics
Adverse Effects

Answer 23

• GI: Nausea and vomiting
• CNS: dizziness, weakness
• CV: hypotension, arrhythmia

Question 24

Class III Antiarrhythmics
Drug Interactions

Answer 24

Numerous
ie.
Digoxin, quinodine, antihistamines, TCAs, phenothiazines

Question 25

**Class IV Antiarrhythmics** Mechanism of Action

Answer 25

* Block the movement of **calcium ions** across the cell membrane, depressing the generation of action potentials and **delaying phases 1 and 2** of repolarization * Slows conduction through the AV node

Question 26

**Class IV Antiarrhythmics** Drug Names

Answer 26

**Diltiazem** **Verapamil** *(Calcium Channel Blockers)*

Question 27

**Class IV Antiarrhythmics** Indications

Answer 27

* Rapid supraventricular dysrhythmias *(rapid afib, atrial flutter, paroxysmal supraventricular tachycardia)*

Question 28

**Class IV Antiarrhythmics** Contraindications

Answer 28

**Absolute:** * Allergy * Sick Sinus Syndrome * Heart Block * CHF * Hypotension **Caution:** * Idiopathic hypertrophic subaortic stenosis *(extra thick heart muscle)* * Pregnancy and lactation * Renal and hepatic impairment

Question 29

**Class IV Antiarrhythmics** Adverse Effects

Answer 29

* **CNS:** dizziness, weakness, fatigue, depression * **GI:** upset * **CV:** hypotension, CHF, shock, edema

Question 30

**Class IV Antiarrhythmics** Drug Interactions

Answer 30

**Numerous** ie. Beta Blockers Digoxin

Question 31

**Antiarrhythmic Therapy** Assessment

Answer 31

* Assess for contraindications and cautions * CNS: level of alertness, speech and vision, reflexes * CV: pulse, BP, HR, rhythm, heart sounds, cardiac monitoring, baseline ECG * Respiratory: rate and depth, lung sounds * Abdomen: bowel sounds * Skin: color, lesions, temperature **Labs:** * CBC * Renal and liver function tests

Question 32

**Antiarrhythmic Therapy** Nursing Diagnoses/Conclusions

Answer 32

* Altered cardiac output *(r/t cardiac effects)* * Altered sensory perception *(r/t CNS effects)* * Injury risk *(r/t adverse effects)* * Knowledge deficit

Question 33

**Antiarrhythmic Therapy** Implementation/Patient Teaching

Answer 33

* Titrate the dose to the smallest amount needed to achieve control of the arrhythmia * Continually monitor cardiac rhythm when starting or changing dose * Ensure that emergency life support equipment is readily available * Administer parenteral forms only if oral form is not feasible * Reduce dose in pts. with renal or hepatic dysfunction * Safety precautions: side rails, lighting, noise control * Periodic monitoring for long term therapy