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56 Cards in this Set
- Front
- Back
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What is an arrythmia?
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Abnormality in impulse
-initiation -conduction -or both |
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How are arrythmias classified and what are these?
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Classified according to anatomic site
1. Supra-ventricular (SA node, Atria, or AV node) 2. Ventricular |
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How do anti-arrhythmic agents work?
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Work to impact electrolyte channels and/or autonomic function
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What are class I agents?
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Na+ channel blockers
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What are the effects of Class I agents on the SA node?
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Increased threshold of excitability
Decreased conduction velocity |
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What are the effects of class I agents on ventricular cells?
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Slower phase 0 depolarization and conduction velocity (slows conduction)
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Which Class I agent has the fastest recovery from channel block? Intermediate? Slowest?
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Fastest: 1B
Intermediate: 1A Slowest: 1C |
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Since class I agents are weak bases, alkalosis ________ activity of class I agents, and acidosis ________ activity of class I agents.
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1. diminishes
2. accentuates |
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How do you treat toxicity of Class I Agents?
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Treat toxicity with Sodium Bicarbonate IV
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Describe phase 0 depolarization, repolarization, and action potential duration of Class IA Agents.
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-Phase 0 depolarization: Moderate
-Repolarization: Prolonged -Action potential duration: Increased |
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Describe phase 0 depolarization, repolarization, and action potential duration of Class IB Agents.
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-Phase 0 depolarization: Mild
-Repolarization: No change or shortened -Action potential duration: Decreased |
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Describe phase 0 depolarization, repolarization, and action potential duration of Class IC Agents.
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-Phase 0 depolarization: Strong
-Repolarization: No change -Action potential duration: No change |
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Which drugs are Class IA Agents?
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Quinidine
Procainamide Disopyramide |
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Quinidine is a natural alkaloid from what substance?
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Cinchona bark
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What is the mechanism of action of Quinidine?
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Blocks Na+ channels
Blocks K+ channels Anticholinergic effects Alpha-adrenergic blocker |
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What are adverse effeccts of quinidine?
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Cinchonism (headache, dizziness, N/V, diarrhea)
Diarrhea (monitor K+!) Anti-cholinergic effects Hypotension (from alpha-blockade) |
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T/F Quinidine has lots of drug interactions?
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True
CYP-450 effects |
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What is Procainamide's mechanism of action?
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Blocks Na+ channels
Blocks K+ channels Less anticholinergic effects than Quinidine No alpha-blocking effects |
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What are the adverse effects of Procainamide?
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Lupus-like Syndrome (ANAs, w/ or w/o rash & joint pain)
Hypotension Torsade's |
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What is the mechanism of action for Disopyramide?
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Blocks Na+ channels
Blocks K+ channels MORE anticholinergic effects than Quinidine No alpha-blocking effects |
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What is the order of anticholinergic effects of Class IA Agents in descending of order of effect?
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Disopyramide > Quinidine > Procainamide
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What are the adverse effects of Disopyramide?
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Anti-cholinergic effects
Depresses heart contractility Torsade's |
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Which drugs are Class Ib Agents?
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Lidocaine
Mexiletine |
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What is Lidocaine's mechanism of action?
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Rapidly blocks Na+ channels
Also utilized as a local anesthetic |
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How do you administer lidocaine?
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IV route only
Huge 1st pass effect |
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What are the adverse effects of Lidocaine?
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Well tolerated, of all Class I agents
Drowsiness/dizziness, slurred speech, blurred vision, lethargy |
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What is the mechanism of action of Mexiletine?
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Blocks Na+ channels
Oral derivative of lidocaine (lower 1st pass effect; oral) |
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What are adverse effects of Mexiletine?
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GI (oral route)
Others similar to lidocaine |
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Which drugs are Class IC Agents?
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Flecainide
Propafenone |
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What is the mechanism of action of Flecainide?
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Blocks Na+ channels
Blocks K+ channels Blocks Ca2+ channels (also blocks RyR2 receptor- SR Ca2+ release) |
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What are the adverse effects of Flecainide?
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Increased mortality (CAST trial)- not to be used in pts w/ structural defects
Negative inotropic effects (worsening CHF) Increased ventricular rate in A. Flutter/ Vent. Re-entry |
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What is the mechanism of action of Propafenone?
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Blocks Na+ channels
Blocks K+ channels Has mild beta-receptor blocking activity |
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What are the adverse effects of Propafenone?
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Bradycardia/Heart block (due to beta-blockade)
Bronchospasm Worsening CHF Ventricular re-entrant tachycardia or increased ventricular rate in A. Flutter |
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What are Class II Agents?
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Beta-blockers
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What does beta-receptor stimulation result in?
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Increased contractility
Increased conduction velocity Decreased nodal refractory period Increased automaticity and heart rate |
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What happens in beta-receptor blockade?
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Decreased automaticity
Increased refractory period Prolonged action potential duration Slowed conduction |
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Which class of anti-arrhythmic agents has demonstrated decreased sudden cardiac death in patients with prior MI?
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Class II Agents (beta-blockers)
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What are anti-arrhythmic uses of beta-blockers?
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Slowing ventricular response to atrial tachy-arrhythmias
Arrhythmias post-MI |
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How do Class III Agents work?
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Inhibit K+ channels
Prolongation of action potential Increased refractory period |
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Which drugs are Class III Agents?
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Amiodarone
Dronedarone Sotalol Dofetilide Ibutilide |
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What is the mechanism of action of Amiodarone?
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Blocks K+, Na+, and Ca2+ channels
Has alpha- and beta-blocker activity |
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What are the adverse effects of Amiodarone?
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Sinus bradycardia and AV nodal blocks
Pulmonary Hepatotoxicity Corneal micro-deposits/Optic neuritis Photosensitivity (blue-gray skin discoloration) Thyroid dysfunction Neuromuscular symptoms |
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What is the mechanism of action of Dronedarone?
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Blocks K+, Na+, Ca2+ channels and alpha-/beta-receptors
Has customary peripheral alpha- and beta-blocker blocker activity (stronger than amiodarone) Decreases mortality in pts w/ A. FIb. |
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What are adverse effects of Dronedarone?
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Worsening HF (don't use in Class IV HF)
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What was included in the black box warning for Dronedarone?
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1. Decompensated HF (Class IV) - increased risk of mortality (2x)
2. Persistent AF (non-convertible) - increased risk of mortality, stroke and hospitalization due to HF (2x) |
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What is the mechanism of action of Sotalol?
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Blocks K+ channels
Has customary peripheral beta-blocker activity Vaughn-Williams Class II and Class III |
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What is the mechanism of action of Dofetilide?
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Only blocks K+ channels
Considered a "pure" Class III agent |
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What is the mechanism of action of Ibutilide?
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Blocks K+ channels
Activates inward Na+ channels |
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How do Class IV Agents work?
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Inhibit Ca2+ channels
Slowed depolarization Increased refractory period and action potential duration |
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Which drugs are the Class IV Agents?
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Diltiazem and Verapamil only (non-dihydropyridines)
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What is the tissue-selectivity for diltiazem? For verapamil?
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Diltiazem: more myocardial than vascular
Verapamil: myocardial |
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What is the mechanism of action of Digoxin?
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Blocks Na+/K+-ATPase pump in AV node - positive inotropic effect
Reduces response to sympathetic tone Indirectly increases vagal tone LOTS of drug interaction |
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What are adverse effects of Digoxin?
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Arrhythmias
GI distress - usually 1st sign of toxicity CNS (visual disturbance, headaches/dizziness, seizures) |
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How do you treat Digoxin overdose?
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Hold Digoxin
Correct electrolyte abnormalities Digoxin Immune Fab (Digibind/Digifab) |
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What is the mechanism of action of Adenosine?
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Activates K+ channels in SA/AV nodes
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What are adverse effects of Adenosine?
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Bronchospasm/Shortness of breath - caution in pts with asthma/COPD
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