Antiarrhythmics - Quiz 4 Flashcards by Donny Le

What happens in Phase 0 of the Cardiac Action Potential?

At -70mV, Na⁺ rushes in and causes Ventricular Contraction until +65mV when the Na⁺ channels inactivate

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What happens in Phase 1 of the Cardiac Action Potential?

Early Rapid Repolarization

Inactive Na⁺ Channel & Open K⁺ Channel for Exit

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What happens in Phase 2 of the Cardiac Action Potential?

Plateau

Slow Ca²⁺ Influx balances out K⁺ Efflux and maintains +10 to -20 mV

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What happens in Phase 3 of the Cardiac Action Potential?

Rapid Repolarization

Inactivated Ca²⁺ Channels & BIG K⁺ Efflux

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What happens in Phase 4 of the Cardiac Action Potential?

Spontaneous Depolarization

ATP Pumps resets all electrolytes back

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What is the diference between Muscle Cell Action Potentials & Automatic SA/AV Cell Action Potentials?

Muscle Cell: Sodium-Dependent Deplarization

SA/AV Cell: Calcium-Dependent Depolarization

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How does an Automaticity Reduction in the Higher Pacemaker Sites affect the Lower Pacemaker Sites?

Automaticity will favor Lower Pacemaker Sites

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What factors reduce the automaticity of higher pacemaker sites?

Vagal Responses

Digitalis Drugs

Parasympathomimetics

Halothane

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What causes Ectopic Foci?

Enhanced Automaticity near the SA Node

Sympathomimetics

Hypercarbia

Hypoxia

Dig. Toxicity

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What can cause Arrythmias from Re-Entry?

Unidirectional Impulse Block from Injury

Alternate Pathway

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In regards to Arrhythmias, where can Re-Entry occur?

Atrium

Ventricle

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What are Type I Antiarrhythmics?

Na⁺ Channel Blockers - Slows Conduction & Prolongs QRS

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What are Type IV Antiarrhythmics?

Ca²⁺ Channel Blockers -

Slows Atrial Rate via SA Node

Slows Conduction via AV Node prolonging P-R Interval

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What are Type III Antiarrhythmics?

K⁺ Channel Blockers -

Slows Conductions & ↑Refractory Period to prolong QT Interval

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What meds are Class Ia Antiarrhythmics and how do they affect the Action Potential?

Slows 0 & Prolongs 3 - Blocks Na⁺ & K⁺ Channels

Quinidine

Procainamide

Disopyramide

Moricizine

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What meds are Class Ib Antiarrhythmics and how do they affect the Action Potential?

Slows 0 & Shortens 3

Lidocaine

Mexilitine

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What meds are Class Ic Antiarrhythmics and how do they affect the Action Potential?

Very Slow Phase 0 - Potent Na⁺ Channel Blocker

Flecainide

Propafenone

MOST PRO-ARRHYTHMIC

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What meds are Class II Antiarrhythmics and how do they affect the Action Potential?

Reduces Phase 4 Slope - ↓Depolarization Rate

Beta-Blockers

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What meds are Class III Antiarrhythmics and how do they affect the Action Potential?

Prolongs Phase 3 - Inhibits K⁺ Channels

Amiodarone

Dronedarone

Sotalol

Ibutilide

Dofetilide

Bretylium

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What meds are Class IV Antiarrhythmics and how do they affect the Action Potential?

Reduces Phase 4 Slope - Inhibits Slow Ca²⁺ Channels

Diltiazem

Verapamil

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Although Amiodarone & Sotalol are Class III Antiarrhythmics that Block K+ Channels, what other channels do they block?

Na+ (Class I)

Beta Receptors (Class II)

Ca²⁺ (Class IV)

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Which class of Antiarrhythmics do Adenosine & Digoxin belong to?

Unclassified

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How does Procainamide work?

Ia Antiarrhythmic

Blocks Na⁺& K⁺ Channels

Converts Unidirectional to Bidirectional Blcok to prevent Re-Entry

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What type of Arrhythmias does Procainamide treat?

Any type of Arrhythmia

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What is the concern when giving Procainamide?

Myocardial Depression Hypotension QT Prolongation Heart Block Ventricular Ectopy Lupus

What the risk of giving multiple doses of Procainamide?

NAPA Metabolite w/ Longer half-life & MORE cardiac side effects

How does Quinidine work?

Ia Antiarrhythmic ↑Excitability Threshold ↓Automaticity Prolongs Action Potential & Refractory

Why does Quinidine also cause Hypotension, Tachycardia, and Atrial Arrhythmias?

It also has Alpha Blockade effects & Vagal Inhibition

When is Quinidine indicated?

A-Fib/Flutter & V-Fib/V-Tach

What are signs of Quinidine Toxicity?

QT Prolongation V-Tach Diarrhea Thrombocytopenia Cinchonism (Tree Bark) - Heachache & Tinnitus

How does Lidocaine Work?

Ib Antiarrhythmic Blocks Na⁺ Channels ↓Phase 4 Slope & Automaticity

How does Disopyramide compare to the other Ia Antiarrhythmics?

Same as Quinidine, but WITHOUT Alpha Effects and WITH Anticholinergic Effects

What are signs of Disopyramide Toxicity?

Acute CHF QT Prolongation Thrombocytopenia Anticholinergic Side Effects

When is Lidocaine used?

Ventricular Arrhythmias & Re-Entry Dysrhythmias (NOT effective for SVT)

What are the side effects of Lidocaine?

Depression to Seizure LV Dysfunction Nystagmus Speech Changes Does NOT prolong QT

When should Lidocaine dosages be reduced?

In patients w/ CHF & Liver Disease

How does Phenytoin work as an Antiarrhythmic?

Ib Antiarrhythmic Blocks Na⁺ Channels Stops Digitalis-Induced Dysrhythmias

What happens if Phenytoin is given too quickly?

Respiratory Arrrest Hypotension Ventricular Ectopy Death

What are the CNS effects of Phenytoin?

Drowsiness Nystagmus Nausea Vertigo

How does Flecainide Work?

Ic Antiarrhythmic Blocks Na⁺, K⁺, & Ca²⁺ Channels ↓Phase 0 Supresses SA node like B-Blockers & CCBs

What are indications for Flecainide?

PVCs Wolf-Parkinsons White Atrial Tachydysrhthmias

When should Flecainide NOT be used due to its Negative Inotropic Effects?

CAD LV Failure V-Tach

How do Beta-Blockers work as Anti-Arrhythmics?

Type II Antiarrythmic Slows SA Node & ↓Phase 4

What are the side effects of Flecainide?

Vertigo Vision Problems Highly Pro-Arrhythmic

Which arrhythmias are Beta-Blockers used for?

SVT A-Fib/Flutter NO Ventricular Arrythmias Effects

What does Amiodarone do?

Type III Anti-Arrhythmic Blocks Na⁺, K⁺, Ca²⁺ Channels Blocks Abnormal Automaticity Anti-Adrenergic (Alpha & Beta) Converts Atrial Arrhythmias to NSR Prolongs PR, QRS, & QT

What kind of Arrhythmias does Amiodarone treat?

Recurrent V-Fib Unstable V-Tach Wolf-Parkinsons White Atrial Arrhythmias

What happens to the Half-Life of Amiodarone when there is prolonged use?

Half-Life Increases

How does Amiodarone affect Anticoagulants?

Increases INR & Bleeding

How does Amiodarone affect Meds that Prolong QT?

Futher Prolongs QT and causes Torsades

How does Amiodarone affect Digoxin & Lidocaine?

Increases Toxicity of Both

How does Amiodarone affect Statins?

Increases Myalgias

How does Amiodarone affect Suggamadex & AV Nodal Blockers?

↑Bradycardia ↑AV Block Sinus Arrest

How does Amiodarone affect Versed?

Prolongs Sedation & ↑Respiratory Depression

What are the Respiratory complications from Amiodarone?

ARDS & Pulmonary Fibrosis

What are the CV complications from Amiodarone?

Bradycardia Hypotension Dysrhythmias Heart Failure Heart Block Sinus Arrest

How does Amiodarone affect the Liver?

Elevated LFTs & Liver Failure

What are the Endocrine complications from Amiodarone?

Hyper/Hypothyroidism

What is Dronedarone?

PO med used to convert A-Fib

Why is Dronedarone not used in patients w/ Heart Failure or Permanent A-Fib?

Worsens HF ↑Stroke ↑Death

When is Dronedarone contraindicated?

2nd & 3rd Degree Blocks Prolonged QT Pregnancy Liver Disease

What is Ibutilide/Dofetilide?

Class III Antiarrhythmic used to convert A-Fib

What is the main Complication of Ibutilide/Dofetilide??

Torsades & V-Tach

How does Verapamil work as an Antiarrhythmic?

Class IV that blocks slow Ca²⁺ channels to prolong SA & AV Nodal Conduction

Which arrhythmias is Verapamil used for?

Atrial Arrhythmias SVT NO effects on accessory paths

What are Verapamil's side effects?

Hypotension Bradycardia Asystole

How does Diltiazem compare to Verapamil as an Antiarrhythmic?

Same, but less significant and MORE DRUG INTERACTIONS

What kind of Arrhythmias does Digoxin treat?

Atrial Arrythmias

When is use of Digoxin as an Antiarrhythmic contraindicated?

Accessory Pathways - WPW Syndrome

How does Adenosine work?

Activates K⁺ channels for _Nodal_ Hyperpolarization causing a transient 3rd degree block and increases refractory

What do the A1 Adenosine receptors do?

Negative Dromotrope & Beta Sympatholytic

What do the A3 Adensoine receptors do?

Negative Inotrope & Dromotrope

When is Adenosine used?

**Paroxysmal SVT (including accessory pathways)** NO effect on A-Fib/Flutter or Arrhythmias distal to AV Node

Which class of Anti-Arrhythmic is most likely to cause Torsades?

**Class Ia & III** - blocks K⁺ channels & prolongs QT

What NON Antiarrhythmic meds prolong QT Intervals?

Antipsychotics Diuretics Antifungals Methadone Aricept Anesthetic Gas Nausea Meds

Which antibiotics prolong QT intervals?

Macrolides & Fluoroquinolones

Which Class of Antiarrhythmics might be the cause of Incessant V-Tach?

1a & 1c