Pharmacology II - Chapter 14 Antiarrhythmics
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Which class of antiarrhythmic drugs is primarily known for blocking sodium channels and prolonging action potential duration?

  • Class 2
  • Class 3
  • Class 1A (correct)
  • Class 1B

    • Which antiarrhythmic drug is indicated for severe ventricular arrhythmias?

  • Amiodarone
  • Diltiazem
  • Flecainide (correct)
  • Lidocaine

    • What is the primary action of Class III antiarrhythmic drugs?

  • Reduce sympathetic autonomic effects
  • Shorten action potential duration
  • Block sodium channels
  • Block potassium currents (correct)

    • Which of the following drugs has minimal to no effect on action potential duration and has a slow binding profile?

    <p>Flecainide</p> Signup and view all the answers

    Which class of antiarrhythmic drugs is primarily associated with reducing beta adrenergic activity in the heart?

    <p>Class II</p> Signup and view all the answers

    What is the primary mechanism of action of Quinidine in treating arrhythmias?

    <p>Sodium channel blockade</p> Signup and view all the answers

    Which statement about Class Ic antiarrhythmic drugs is accurate?

    <p>They are effective only after other antiarrhythmics have failed.</p> Signup and view all the answers

    What is a major clinical concern associated with Sotalol as a Class III antiarrhythmic?

    <p>Precipitation of Torsade de Pointes arrhythmia</p> Signup and view all the answers

    How do beta blockers function in the context of treating arrhythmias?

    <p>They reduce sodium and calcium currents and suppress abnormal pacemakers.</p> Signup and view all the answers

    What distinguishes Class Ib antiarrhythmic drugs from other classes?

    <p>They can lead to a high first-pass effect and are used exclusively at sodium channels.</p> Signup and view all the answers

    Which of the following is NOT classified as an arrhythmia?

    <p>Myocardial infarction</p> Signup and view all the answers

    What distinguishes atrial flutter from atrial fibrillation?

    <p>Atrial flutter typically involves a single reentrant circuit.</p> Signup and view all the answers

    Which of the following factors can cause an arrhythmia?

    <p>Change in conduction velocity</p> Signup and view all the answers

    In the context of cardiac action potentials, which statement is true?

    <p>Different phases of action potentials are determined by specific ion flows.</p> Signup and view all the answers

    Which mechanism is NOT associated with arrhythmias?

    <p>Normal conduction pathways</p> Signup and view all the answers

    Torsade de pointes is typically characterized by which of the following?

    <p>Polymorphic ventricular tachycardia with an increased QT interval.</p> Signup and view all the answers

    In terms of cardiac cell ion flux, what is true?

    <p>Each cardiac myocyte channel is specific to a single ion.</p> Signup and view all the answers

    Ohm's Law in relation to cardiac arrhythmias is relevant for understanding what concept?

    <p>Current flow relative to voltage and conductance.</p> Signup and view all the answers

    What is the primary function of the atrioventricular (AV) node in the cardiac conduction system?

    <p>To distribute electrical impulses to the ventricles</p> Signup and view all the answers

    Which antiarrhythmic drug is indicated for maintaining normal sinus rhythm in patients with heart failure?

    <p>Amiodarone</p> Signup and view all the answers

    Which part of the heart's electrical system is referred to as the 'natural pacemaker'?

    <p>SA node</p> Signup and view all the answers

    What is the primary use of Amiodarone in arrhythmias?

    <p>As a broad-spectrum agent used when all other treatments fail.</p> Signup and view all the answers

    Which side effect is most commonly associated with Class IV antiarrhythmic drugs?

    <p>Constipation.</p> Signup and view all the answers

    In the context of antiarrhythmic therapy, what is a critical consideration before initiating treatment?

    <p>Confirming the specific type of arrhythmia present.</p> Signup and view all the answers

    What significant toxicity is associated with the use of Verapamil, a Class IV drug?

    <p>Severe constipation.</p> Signup and view all the answers

    Which part of the cardiac conduction system initiates the conduction of an electrical signal?

    <p>His bundle</p> Signup and view all the answers

    During which phase of the action potential do Class I drugs primarily act?

    <p>Phase 0 - Rapid depolarization</p> Signup and view all the answers

    Which ion concentration is significantly higher extracellularly compared to intracellularly in cardiac cells?

    <p>Na+</p> Signup and view all the answers

    What is the primary consequence of abnormal automaticity in the heart?

    <p>Erratic heart rhythms</p> Signup and view all the answers

    Which of the following ions is primarily responsible for the plateau phase in cardiac action potentials?

    <p>Ca++</p> Signup and view all the answers

    What is the role of the His-Purkinje system in the heart?

    <p>To conduct electrical impulses throughout ventricles</p> Signup and view all the answers

    What characterizes Class III drugs in relation to cardiac action potentials?

    <p>Prolong repolarization phase</p> Signup and view all the answers

    What drugs are well tolerated in heart failure (reduced ejection volume) and have the ability to convert or prevent atrial fibrillation?

    <p>Dofetilide</p> Signup and view all the answers

    What is used to reverse digoxin-induced arrhythmias?

    <p>Digoxin immune fab</p> Signup and view all the answers

    What may precipitate torsade de pointes arrhythmia?

    <p>Sotalol</p> Signup and view all the answers

    What is the mechanism of action (MOA) of adenosine?

    <p>Activates K+ channels and blocks calcium channels</p> Signup and view all the answers

    What is the importance of magnesium?

    <p>May act on ATPase enzyme, Na channels, certain K channels, and Ca channels; often used to treat torsades de pointes</p> Signup and view all the answers

    What can hypokalemia induce?

    <p>Ectopic pacemaker activity</p> Signup and view all the answers

    Match each drug glass to its indications

    <p>Class 1 A = AF, PVC Class 1B = PVCs Class 2 = AF, atrial flutter, PVCs Class 1C = Severe ventricular arrhythmia</p> Signup and view all the answers

    Match each drug class to its indiciations

    <h1>Class 3 = AF, Severe ventricular arrythmias Class 4 = AF, atrial flutter</h1> <p>=</p> Signup and view all the answers

    Study Notes

    Pharmacology II - Chapter 14 Antiarrhythmics

    • Case Study 1:

      • 69-year-old female with a one-month history of palpitations, shortness of breath, and fatigue.
      • Hypertension history.
      • ECG shows atrial fibrillation with a ventricular response of 122 bpm.
      • Echocardiogram reveals a 38% left ventricular ejection fraction.
      • Rhythm reverted to normal after seven days of metoprolol treatment.
      • Patient still experiences atrial fibrillation paroxysms.
      • Question: What antiarrhythmic drug is appropriate for maintaining a normal sinus rhythm?

    • Case Study 2:

      • A drug well-tolerated in heart failure (reduced ejection volume) and with the ability to convert or prevent atrial fibrillation is required.
      • Possible drug options: amiodarone or dofetilide.

    Normal Cardiac Rhythm

    • Sinoatrial (SA) node initiates electrical impulses at a rate of 60-100 beats per minute.
    • Impulse spreads through the atria and then to the atrioventricular (AV) node.
    • Impulse travels through the His-Purkinje fibers to the ventricles.
    • Ventricles contract.

    Cardiac Conduction System

    • SA node (pacemaker) located in the right atrium.
    • Electrical impulses generated by the SA node.
    • AV node located between the atria and ventricles, acting as an electrical bridge.
    • His-Purkinje system composed of His bundle, right bundle branch, left bundle branch, and Purkinje fibers.

    Mechanisms of Arrhythmias

    • Abnormal automaticity or reentrant conduction.

    • Examples of arrhythmias include atrial flutter, atrial fibrillation, AV nodal reentry, premature ventricular beats (PVBs), ventricular tachycardia, and ventricular fibrillation.

    • Arrhythmia causes:

      • Abnormal site of impulse origin
      • Change from normal in rate or regulatory control
      • Change in conduction velocity

    • Cardiac cell electrical potential controlled by ion flux through cell pores/gates.

    Action Potential Phases (Cardiac Cell)

    • Phase 0: Rapid depolarization.
    • Phase 1: Early-fast repolarization.
    • Phase 2: Plateau.
    • Phase 3: Repolarization.
    • Phase 4: Diastole, resting potential.

    ECG/EKG

    • P wave: Atrial depolarization.
    • QRS complex: Ventricular depolarization.
    • T wave: Ventricular repolarization.
    • PR interval: Conduction time from atrium to ventricle.
    • QRS duration: Time required for ventricular activation (intraventricular conduction time).
    • QT interval: Reflects the duration of the ventricular action potential.

    Table 1: Antiarrhythmic Drugs

    • Includes different drug classes (1A, 1B, 1C, 2, 3, 4) and their corresponding drugs, like quinidine, lidocaine, flecainide, esmolol, amiodarone, sotalol
    • Provides specific indications for each drug class.

    Mechanisms of Antiarrhythmic Drugs

    • Block sodium channels.
    • Block sympathetic autonomic effects.
    • Prolongation of refractory period.
    • Block calcium channels.

    Classes of Antiarrhythmic Drugs

    • Class I: Sodium channel blockers (Ia, Ib, Ic).
      • Local anesthetics.
      • Vary in binding affinity to sodium channels.
      • Prolongation or shortening of action potential duration.
    • Class II: Beta-blockers (reduce beta adrenergic activity in the heart).
    • Class III: Potassium channel blockers (prolong action potential duration).
    • Class IV: Calcium channel blockers (block calcium currents).

    Additional Antiarrhythmic Drugs

    • Adenosine (endogenous and used in high doses for AV nodal arrhythmias).
    • Magnesium (less specific class designation and mechanism of action)

    Principles in Clinical Use of Antiarrhythmic Agents

    • Eliminate underlying causes, such as electrolyte imbalances or drug interactions.
    • Accurately diagnose the arrhythmia.
    • Assess baseline conditions of the patient (e.g., heart failure, other cardiac diseases).
    • Question the necessity for drug therapy.

    Specific Drugs (detailed information)

    • Quinidine:

      • Class Ia sodium channel blocker.
      • Prolonged QRS duration.
      • Major cardiac effects: QT interval prolongation, induction of Torsade de Pointes arrhythmia, and syncope.
      • Extraction of quinine from cinchona bark led to quinidine discovery.

    • Procainamide: Hypotension and lupus erythematosus (L. wolf)

    • Lidocaine: Used in acute ventricular arrhythmias caused by ischemia following MI. High first-pass effect.

    • Amiodarone: Used for a broad spectrum of arrhythmias. High toxicity. Deposits in cornea and skin. Causes thyroid dysfunction.

    • Esmolol: Used IV only for acute arrhythmias.

    • Propranolol, metoprolol, timolol: Used as prophylactic drugs in patients following MI.

    • Sotalol: High toxicity. May precipitate torsades de pointes arrhythmia.

    • Flecainide: Used for both atrial and ventricular arrhythmias. High mortality rates.

    • Verapamil: Key toxicity is constipation, nausea, flushing, and dizziness. Can lead to heart failure.

    • Adenosine: Slows or blocks conduction. Blocks AV nodal arrhythmias.

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    PM 719 Pharmacology II - Chapter 14 Antiarrhythmics PDF

    Description

    Explore key concepts in antiarrhythmic pharmacology through case studies. This quiz covers the mechanisms and options for maintaining normal sinus rhythm, especially in patients with atrial fibrillation. Test your knowledge on drug choices and cardiac rhythms.

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