Antiarrhythmic Agents Flashcards
What are the 5 phases of the Action Potential of the Cardiac Muscle Cell?
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)
What are some causes of Cardiac Arrhythmias?
- 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
How do the classifications of Antiarrhythmics work?
Class I: Block sodium channels
Class II: Act on autonomic receptors
Class III: Block potassium channels
Class IV: Block calcium channels
Lifespan considerations of Antiarrhythmics
In Children
- 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
Lifespan considerations of Antiarrhythmics
In Adults
- Used frequently during emergencies
- Monitor frequently
- Avoid use in pregnancy and lactation (alternative feeding method needed)
Lifespan considerations of Antiarrhythmics
In Older Adults
- Frequently prescribed
- More likely to experience adverse effects
- Start low
Class I Antiarrhythmics
Sub-Classes and Drug Names
- Ia: Procainamide, quinidine
- Ib: Lidocaine
- Ic: Flecainide, propafenone
Class I Antiarrhythmics
Mechanism of Action
- 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
Class I Antiarrhythmics
Indications
- Tachycardia
- Life-threatening ventricular arrythmias
- Symptomatic paroxysmal atrial arrhythmias
Class I Antiarrhythmics
Contraindications
Absolute:
* Allergy
* Bradycardia, heart block
* CHF
* Hypotension, shock
* Electrolyte disturbances
Cautions:
* Renal or hepatic dysfunction
* Pregnancy or lactation
Class I Antiarrhythmics
Adverse Effects
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
Class I Antiarrhythmics
Drug Interactions
Numerous
ie. Cemetidine, Digoxin, warfarin
Food:
Quinidine: foods that alkanalize the urine (citrus juice, vegetables, antacids, milik products); grapefruit juice
Class II Antiarrhythmics
Mechanism of Action
- “-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
Class II Antiarrhythmics
Indications
- 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
Class II Antiarrhythmics
Drug Names
Acebutolol
Esmolol
Propranolol
Digoxin
Adenosine
Class II Antiarrhythmics
Contraindications
Absolute:
* Allergy
* Sinus bradycardia
* AV block
* Cardiogenic shock
* Respiratory Depression
Caution:
* Diabetes
* Thyroid dysfunction
* Asthma or COPD
* Pregnancy and lactation
* Renal and hepatic dysfunction
Class II Antiarrhythmics
Adverse Effects
- CNS: Dizziness, insomnia, dreams, fatigue
- CV: hypotension, bradycardia, AV block, arrhythmias
- Respiratory: Bronchospasm, dyspnea
- GI: Nausea, vomiting, anorexia
Class II Antiarrhythmics
Drug Interactions
- Verapamil or diltiazem (increased risk of CV effects)
- Antidiabetic medications
- Methylxanthines
Class III Antiarrhythmics
Mechanism of Action
- Block potassium channels and slow outward movement of potassium during Phase 3 of the action potential (prolonging it)
Class III Antiarrhythmics
Indications
- Life-threatening ventricular arrhythmias
- Maintenance of sinus rhythm after conversion of atrial arrhythmias
Class III Antiarrhythmics
Contraindications
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
Class III Antiarrhythmics
Drug Names
Sotalol
Amiodarone
Dofetilide
(SAD)
Class III Antiarrhythmics
Adverse Effects
- GI: Nausea and vomiting
- CNS: dizziness, weakness
- CV: hypotension, arrhythmia
Class III Antiarrhythmics
Drug Interactions
Numerous
ie.
Digoxin, quinodine, antihistamines, TCAs, phenothiazines
Class IV Antiarrhythmics
Mechanism of 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
- Slows conduction through the AV node
Class IV Antiarrhythmics
Drug Names
Diltiazem
Verapamil
(Calcium Channel Blockers)
Class IV Antiarrhythmics
Indications
- Rapid supraventricular dysrhythmias (rapid afib, atrial flutter, paroxysmal supraventricular tachycardia)
Class IV Antiarrhythmics
Contraindications
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
Class IV Antiarrhythmics
Adverse Effects
- CNS: dizziness, weakness, fatigue, depression
- GI: upset
- CV: hypotension, CHF, shock, edema
Class IV Antiarrhythmics
Drug Interactions
Numerous
ie.
Beta Blockers
Digoxin
Antiarrhythmic Therapy
Assessment
- 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
Antiarrhythmic Therapy
Nursing Diagnoses/Conclusions
- Altered cardiac output (r/t cardiac effects)
- Altered sensory perception (r/t CNS effects)
- Injury risk (r/t adverse effects)
- Knowledge deficit
Antiarrhythmic Therapy
Implementation/Patient Teaching
- 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
