Download 22-Antidysrhythmics

Antidysrhythmic Agents
Chapter 22
Antidysrhythmics
Dysrhythmia
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Any deviation from the normal rhythm of the
heart
Antidysrhythmics
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Drugs used for the treatment and prevention
of disturbances in cardiac rhythm
Cardiac Cell
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Inside the cardiac cell, there exists a
net negative charge relative to the
outside of
the cell.
Resting Membrane Potential:
RMP
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This difference in the electronegative
charge.
Results from an uneven distribution of
ions (sodium, potassium, calcium)
across the cell membrane.
An energy-requiring pump is needed to
maintain this uneven distribution of
ions.
Sodium-potassium ATPase pump
Action Potential
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A change in the distribution of ions causes cardiac
cells to become excited.
The movement of ions across the cardiac cell’s
membrane results in the propagation
of an electrical impulse.
This electrical impulse leads to contraction
of the myocardial muscle.
Action Potential
Four Phases

The SA node and the Purkinje cells each have
separate action potentials.
Vaughan Williams
Classification

System commonly used to classify
antidysrhythmic drugs
Vaughan Williams
Classification

Class 1
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Class Ia
Class Ib
Class Ic
Class II
Class III
Class IV
Other
Vaughan Williams
Classification
Class I
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Membrane-stabilizing agents
Fast sodium channel blockers
Divided into Ia, Ib, and Ic agents, according
to effects
Vaughan Williams
Classification
Class I
moricizine
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General Class I agent
Has characteristics of all three subclasses
Used for symptomatic ventricular and lifethreatening dysrhythmias
Vaughan Williams
Classification
Class Ia
quinidine, procainamide, disopyramide
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Block sodium channels
Delay repolarization
Increase the APD
Used for atrial fibrillation, premature atrial
contractions, premature ventricular
contractions, ventricular tachycardia, WolffParkinson-White syndrome
Vaughan Williams
Classification
Class Ib
tocainide, mexiletine, phenytoin, lidocaine
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Block sodium channels
Accelerate repolarization
Decrease the APD
Used for ventricular dysrhythmias only
(premature ventricular contractions,
ventricular tachycardia, ventricular fibrillation)
Vaughan Williams
Classification
Class Ic
encainide, flecainide, propafenone
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Block sodium channels (more pronounced
effect)
Little effect on APD or repolarization
Used for severe ventricular dysrhythmias
May be used in atrial fibrillation/flutter
Vaughan Williams
Classification
Class II
Beta blockers: atenolol, esmolol,
petaprolol, propranolol
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Reduce or block sympathetic nervous system
stimulation, thus reducing transmission of
impulses in the heart’s conduction system
Depress phase 4 depolarization
General myocardial depressants for both
supraventricular and ventricular dysrhythmias
Vaughan Williams
Classification
Class III
amiodarone, bretylium, sotalol, ibutilide
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Increase APD
Prolong repolarization in phase 3
Used for dysrhythmias that are difficult to
treat
Life-threatening ventricular tachycardia or
fibrillation, atrial fibrillation or flutter—
resistant to other drugs
Vaughan Williams
Classification
Class IV
verapamil, diltiazem
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Calcium channel blockers
Depress phase 4 depolarization
Used for paroxysmal supraventricular
tachycardia; rate control for atrial fibrillation
and flutter
Vaughan Williams
Classification
Other Antidysrhythmics
digoxin, adenosine

Have properties of several classes and are not
placed into one particular class
Antidysrhythmics
Digoxin
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Cardiac glycoside
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Inhibits the sodium-potassium ATPase pump
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Positive inotrope—improves the strength of cardiac
contraction
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Allows more calcium to be available for contraction
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Used for CHF and atrial dysrhythmias
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Monitor potassium levels, drug levels, and
for toxicity
Antidysrhythmics
adenosine (Adenocard)
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Slows conduction through the AV node
Used to convert paroxysmal supraventricular
tachycardia to sinus rhythm
Very short half-life
Only administered as fast IV push
May cause asystole for a few seconds
Other side effects minimal
Antidysrhythmics: Side Effects
ALL antidysrhythmics can cause
dysrhythmias!!
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Hypersensitivity reactions
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Nausea
Vomiting
Diarrhea
Dizziness
Blurred vision
Headache
Antidysrhythmics:
Nursing Implications
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Obtain a thorough drug and medical
history.
Measure baseline BP, P, I & O, and
cardiac rhythm.
Measure serum potassium levels before
initiating therapy.
Antidysrhythmics:
Nursing Implications
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Assess for conditions that may be
contraindications for use of specific
agents.
Assess for potential drug interactions.
Instruct patients regarding dosing
schedules and side effects to report to
physician.
Antidysrhythmics:
Nursing Implications
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During therapy, monitor cardiac rhythm,
heart rate, BP, general well-being, skin
color, temperature, heart and breath
sounds.
Assess plasma drug levels as indicated.
Monitor for toxic effects.
Antidysrhythmics:
Nursing Implications
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Instruct patients to take medications as
scheduled and not to skip doses or
double up for missed doses.
Patients who miss a dose should
contact their physician for instructions if
a dose is missed.
Instruct patients not to crush or chew
any oral sustained-release preparations.
Antidysrhythmics:
Nursing Implications
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For class I agents, monitor ECG for QT
intervals prolonged more than 50%.
IV infusions should be administered
with
an IV pump.
Antidysrhythmics:
Nursing Implications
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Patients taking propranolol, digoxin, and
other agents should be taught how to
take their own radial pulse for 1 full
minute, and to notify their physician if
the pulse is less than 60 beats/minute
before taking the next dose of
medication.
Antidysrhythmics:
Nursing Implications
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Monitor for therapeutic response:
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Decreased BP in hypertensive patients
Decreased edema
Regular pulse rate or
Pulse rate without major irregularities, or
Improved regularity of rhythm
What would you do????