Questions and Answers
What is automaticity?
Ability of cardiac cells to depolarize spontaneously.
What is proarrhythmia?
The provocation of a new arrhythmia or the aggravation of a pre-existing one during therapy with a drug at doses or plasma concentrations below those considered to be toxic.
What are pacemaker cells responsible for?
Cardiac rate (aka chronotropy).
What are cardiac myocytes?
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What does H's and T's of ACLS stand for? (Select all that apply)
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What may cause a proarrhythmia?
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What are some arrhythmia treatments? (Select all that apply)
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What is the Vaughan Williams classification used for?
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What is the primary action of Class I antiarrhythmic drugs?
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What is the mechanism of action for Class IA drugs?
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What EKG changes are associated with Class IA drugs?
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Which of the following are Class IA drugs? (Select all that apply)
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What is the primary effect of Class IB drugs on phase 0 depolarization?
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What EKG changes are associated with Class IB drugs?
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What are Class IC drugs known for? (Select all that apply)
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Which of the following are Class IC drugs? (Select all that apply)
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What characterizes Class II antiarrhythmic drugs?
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What EKG changes are typically seen with Class II drugs?
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What are Class III antiarrhythmic drugs primarily used for?
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What potential EKG changes may occur with Class III drugs?
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Which of the following are Class III drugs? (Select all that apply)
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What is the mechanism of action of Amiodarone?
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What are the black box warnings associated with Amiodarone?
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Study Notes
Automaticity and Cardiac Function
- Automaticity refers to cardiac cells' ability to spontaneously depolarize.
- Pacemaker cells are responsible for rhythmically controlling heart rate, while cardiac myocytes enable contraction through depolarization.
Proarrhythmia and H's and T's
- Proarrhythmia is the exacerbation of arrhythmias during drug therapy, even at non-toxic doses.
- The H's and T's of Advanced Cardiac Life Support (ACLS) include:
- Hypovolemia, Hypoxia, Hydrogen ions (acidosis), Hypothermia
- Toxins, Thrombosis (pulmonary or coronary), Trauma, Tamponade, Tension pneumothorax
Treatments for Arrhythmia
- Treatment options include:
- Antiarrhythmic drugs
- Cardioversion and defibrillation
- Implantable cardioverter-defibrillators (ICDs)
- Pacemakers with cardiac resynchronization therapy
- Catheter ablation
- Surgery
Vaughan Williams Classification
- A system that categorizes antiarrhythmic drugs based on their primary electrophysiological effects.
Classes of Antiarrhythmic Drugs
- Class I: Sodium channel blockers that reduce phase 0 depolarization, divided into three subgroups (A, B, C).
Class IA Antiarrhythmics
- Moderate inhibition of phase 0 depolarization with intermediate kinetics.
- Associated with widened QRS and prolonged QT interval, increasing the risk of ventricular tachycardia.
- Key drugs include Disopyramide, Quinidine, and Procainamide.
Class IB Antiarrhythmics
- Display weak effects on phase 0 depolarization with fast kinetics.
- Result in narrowed QRS and shortened QT interval.
- Include Lidocaine and Mexiletine, with concerns for hepatotoxicity and complications in patients with structural heart disease.
Class IC Antiarrhythmics
- Have a significant effect on phase 0 depolarization due to powerful sodium channel blockage and slow kinetics.
- They pose risks of proarrhythmias and severe issues in those with structural heart disease.
- Notable drugs are Flecainide and Propafenone.
Class II Antiarrhythmics
- Consist mainly of beta blockers, excluding sotalol.
- Associated EKG changes include increased PR interval.
Class III Antiarrhythmics
- Comprised of potassium channel blockers, leading to delayed repolarization.
- Can increase QT interval with a risk of Torsades de Pointes.
- Important drugs include Dronedarone, Amiodarone, Dofetilide, Ibutilide, and Sotalol.
Amiodarone Characteristics
- A unique potassium channel blocker with several potential toxicities, including pulmonary and hepatic concerns.
- Known for its slow and variable absorption, long half-life (58 days), and broad spectrum of use.
- FDA warnings include proper usage and risk of proarrhythmic effects.
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Explore key concepts related to antiarrhythmic drugs with these flashcards. Each card provides a critical term along with its definition to enhance your understanding of cardiac physiology and pharmacology. Perfect for students and professionals studying cardiology.