Antiarrhythmic Agents

Question 1

5 Phases of the Action Potential of the Cardiac Muscle Cell

Answer 1

Phase 0: sodium ions move into cells
Phase 1: potassium ions move out of cells
Phase 2: Calcium ions move into cells
Phase 3: Potassium ions move out of cells
Phase 4: Back at rest and ready to start again

Question 2

Causes of Cardiac Arrhythmias

Answer 2

Electrolyte disturbances that alter the action potential
Decreases in oxygen delivered to the cells
structural damage changing the conduction pathway through the heart
Acidosis or accumulation of waste products altering the action potential
Drugs that alter the action potential or cardiac conduction

Question 3

Types of Cardiac Arrhythmias

Answer 3

Tachycardia
Bradycardia
Premature atrial contractions (PACs) or premature ventricular contractions (PVCs)
Atrial Flutter
Atrial fibrillation or ventricular fibrillation
Alterations in conduction through the muscle (heart blocks and bundle branch blocks)

Question 4

Classifications of Antiarrhythmics

Answer 4

Class I: Block the sodium channels in the cell membrane during an action potential (phase 0)
Class II: Block beta-receptors causing a depression of phase 4 of the action potential
Class III: block potassium channels, prolong phase 3 of the action potential
Class IV: Block calcium channels in the cell membrane (phase 2)

Question 5

Children

Use of Antiarrhythmic Across the Lifespan

Answer 5

Monitor closely - more likely to experience ADE
Digoxin is approved in children
Dosages should be calculated by age and weight
Ablation procedures have been successful

Question 6

Adults

Use of antiarrhythmic across the lifespan

Answer 6

Used frequently during emergencies
Monitor frequently
avoid use in pregnancy/lactation

Question 7

Older Adults

use of antiarrhythmics across lifespan

Answer 7

Frequently prescribed
More likely to experience ADE
start at lower dose

Question 8

Sub-Classes of Class I Antiarrhythmic drugs

Answer 8

Block the sodium channels in the cell membrane during an action potential
Ia: Disopyramide, procainamide, quinidine
Ib: Lidocaine (prototype), mexiletine
Ic: Flecainide, propafenone

Question 9

Class I Antiarrhythmic

Answer 9

Actions: Decreases depolarization, decreasing automaticity of the ventricular cells; increases ventricular fibrillation threshold
Indications: Management of acute ventricular arrhythmias during cardiac surgery or MI
Contraindications: Allergy, bradycardia or heart block, CHF, hypotension or shock, electrolyte disturbances
Caution: Renal or hepatic dysfunction or pregnancy
ADE: dizziness, fatigue, slurred speech; nausea/vomiting; arrhythmias; respiratory depression; rash, loss of hair and potential bone marrow suppression
DDI: quinidine and digoxin; oral anticoagulants; digoxin and beta-blockers
Drug-Food: foods that alkalinize the urine (citrus juice, veggies, antacids, milk products) grapefruit juice

Question 10

Mnemonic for Subclasses of Antiarrhythmics

Answer 10

Class 1a: "double quarter pounder" = Disophyramide, quinidine, procainamide
Class 1b: "with lettuce, mayo and tomato" = Lidocaine, mexiletine, tocainide
class 1c: "and more fries please!" = moricizine, flecainide, propefanone

Question 11

Class II Antiarrhythmic

“-olol”

Answer 11

Acebutolol, esmolol, propranolol (prototype)
Action: Beta-adrenergic blockers block beta receptors causing a depression of phase 4 of the action potential; Competitively block beta receptor sites in the heart and kidneys –> decrease heart rate, cardiac excitability and cardiac output –> slow conduction through the AV node
Indication: Treatment of supra ventricular tachycardia and PVCs
Contraindications: Sinus Brady Cardia, AV Block, cardiogenic shock, CHF, asthma, respiratory depression, pregnancy/lactation
Cautions: Diabetes thyroid dysfunction, renal or hepatic dysfunction
ADE: Related to the effects of blocking beta receptors in the sympathetic nervous system - dizziness, insomnia, dreams and fatigue; hypotension, bradycardia, AV block, arrhythmias; bronchospasm and dyspnea; nausea/vomiting, anorexia; loss of libido, decreased exercise tolerance, alterations in blood glucose levels
DDI: Verapamil, insulin

Question 12

Class III Antiarrhythmic

Answer 12

Amiodarone (prototype), dofetilide, sotalol
Action: Block potassium channels and slow the outward movement of potassium during phase 3 of the action potential, prolonging it
Indications: life threatening ventricular arrhythmias; maintenance of sinus rhythm after conversion of atrial arrhythmias
Contraindications: when used for life threatening arrhythmias, there is no contraindications
Caution: Shock, hypotension, respiratory depression, prolonged QT interval, renal or hepatic disease
ADE: Nausea/vomiting, weakness, dizziness, arrhythmia
DDI: digoxin or quinidine; other specific drug interactions vary with individual drugs

Question 13

Class III Mnemonic

Answer 13

Class III: SAD banana = Sotalol, Amiodarone, Dofelitide

Question 14

Class IV Antiarrhythmic

Answer 14

Diltiazem (prototype), Verapamil
Action: Block the movement of calcium ions across the cell membrane, depressing the generation of action potentials and delaying phases 1 and 2 of repolarization, which slows automaticity and conduction in the AV node
Indication: Supraventricular tachycardia (SVT); control the ventricular response to rapid atrial rates
Contraindications: Allergy, sick sinus syndrome or heart block, pregnancy/lactation, CHF, hypotension
Caution: Idiopathic hypertrophic subaortic stenosis, renal and liver impairment
ADE: dizziness, weakness, fatigue, depression, GI upset, hypotension, CHF, shock
DDI: many of them

Question 15

Class IV Mnemonic

Answer 15

Class IV: Very Dairy = Verapamil Diltiazem

Question 16

Other drugs used to treat arrhythmias

Answer 16

Adenosine
Digoxin
Dronedarone

Question 17

Adenosine

Answer 17

Used to convert supraventricular tachycardia to sinus rhythm when vagal maneuvers have been ineffective

Question 18

Digoxin

Answer 18

Slows calcium from leaving the cell, prolonging the action potential and slowing conduction and heart rate

Question 19

Dronedarone

Answer 19

Used to reduce risk of hospitalization in patients with paroxysmal or persistent AF or flutter who have risk factors for CVD and are in sinus rhythm or scheduled to be converted to sinus rhythm

Question 20

Nursing Considerations for Antiarrhythmic Therapy

Answer 20

Assess: History and physical exam; known allergy; impaired kidney or liver function, heart block, HF, hypotension, shock, respiratory dysfunction, electrolyte disturbances; Pregnancy and lactation. neurological and cardiac status, respirations, baseline ECG and appropriate lab values
Nursing Diagnoses: Decreased cardiac output related to cardiac effects; disturbed sensory perception r/t CNS effects; risk for injury r/t adverse drug effects; deficient knowledge
Implementation: Titrate dose to the smallest amount needed to achieve control of arrhythmia; continually monitor cardiac rhythm when initiating or changing dose; ensure that emergency life support equipment is readily available; administer parenteral forms as ordered only if the oral form is not feasible; consult with prescriber to reduce dose in patients with renal or hepatic dysfunction; establish safety precautions (side rails, lighting, noise control) if CNS effects occur; arrange for periodic monitoring of cardiac rhythm for long-term therapy