Presentation on theme: "Drugs for Dysrhythmias 19. Learning Outcomes 1. Explain how rhythm abnormalities can affect cardiac function. 2. Illustrate the flow of electrical impulses."— Presentation transcript:
Drugs for Dysrhythmias 19
Learning Outcomes 1. Explain how rhythm abnormalities can affect cardiac function. 2. Illustrate the flow of electrical impulses through the normal heart. 3. Classify dysrhythmias based on their location and type of conduction abnormality.
Learning Outcomes 4. Explain the importance of ion channels to cardiac function and the pharmacotherapy of dysrhythmias. 5. Identify the importance of nonpharmacologic therapies in the treatment of dysrhythmias. 6. Identify basic mechanisms by which antidysrhythmic drugs act.
Learning Outcomes 7. For each of the classes in the Drug Snapshot, identify representative drugs, explain their mechanisms of action, primary actions, and important adverse effects: 8. Categorize antidysrhythmic drugs based on their classifications and mechanisms of action.
Core Concept 19.1 Some types of dysrhythmias produce no patient symptoms, whereas others may be life threatening.
Core Concept 19.6 Sodium channel blockers slow the rate of impulse conduction through the heart.
Sodium Channel Blockers Largest group of antidysrhythmics Three subgroups IA, IB, and IC Based on subtle differences in their mechanisms of action
Sodium Channel Blockers Because progression of the action potential depends on the opening of sodium ion channels, a blockade of these channels will slow the spread of impulse conduction across the myocardium
Core Concept 19.7 Beta-adrenergic blockers reduce automaticity and slow conduction velocity in the heart.
Beta Blockers Ability to slow the heart rate and conduction velocity can suppress several types of dysrhythmias. Slow the heart rate Decrease conduction velocity through the AV node.
Beta Blockers Myocardial automaticity is reduced Many types of dysrhythmias are stabilized Main value is to treat atrial dysrhythmias associated with heart failure.
Core Concept 19.8 Potassium channel blockers prolong the refractory period of the heart.
Potassium Channel Blockers Blocks potassium ion channels in myocardial cells Prolong the duration of the action potential by lengthening the refractory period (resting stage) Stabilizes dysrhythmias.
amiodarone (Pacerone, Cordarone)
Core Concept 19.9 Calcium channel blockers are available to treat supraventricular dysrhythmias.
Calcium Channel Blockers Slowconduction velocity Stabilize certain dysrhythmias Effects include Reduced automaticity in the SA node Slowed impulse conduction through the AV node Prolongs the refractory period Stabilizes many types of dysrhythmias
Calcium Channel Blockers Only effective against supraventricular dysrhythmias.
Core Concept Digoxin and adenosine are used for specific dysrhythmias, but do not act by blocking ion channels.
Adenosine (Adenocard, Adenoscan) Given as a 1- to 2-second bolus IV injection Actions Terminates serious atrial tachycardia Slows conduction through the AV node decreases automaticity of the SA node
Adenosine (Adenocard, Adenoscan) Primary indication Paroxysmal supraventricular tachycardia (PSVT), for which it is a drug of choice 10-second half-life, adverse effects are generally self-limiting.
Digoxin (Lanoxin, others) Primarily used to treat heart failure Prescribed for certain types of atrial dysrhythmia Decreases automaticity of the SA node Slows conduction through the AV node