Antidysrhythmic Drugs - Ch. 52 Flashcards
What is a dysrhythmia?
Any deviation from the normal rate/rhythm of the heart
What is an arrhythmia?
βno rhythmβ
What is Asystole?
No heartbeat
What are tachydysrhythmias?
Increased heart rate
-More common
-treated with drugs and other stuff
What are bradydysrhythmias?
Slowed heart rate
Electrical pacing
-Treated with Atropine
What caused dysrhythmias?
Ischemic heart disease
MI
Cardiomyopathy
myocarditis
electrolyte imbalanses (e.g, abnomral K+ level)
What are antidysrythmics?
Drugs used for the treatment and prevention in cardiac rate and/or rhythm
Most antidysrythmics do what?
Supress abnormal electrical impulse formation or conduction
What produces cardiac electrical activity?
SA node cells
AV node cells
Purkinje fibres cells
Ventricular cells
-Electrical activity differs with each cell type
What results in action potential in cardiact muscle?
Movement of ions across the cardiac cell membranes
What does action potential cause the contarction of?
Myocaridal muscle
In SA and AV node cells what does action potential depend on?
Ca2+ influx via calcium channels
In ventricular/atrial cardiac muscle cells how does action potential start?
With Na+ influx (depolarization) via sodium channels
In ventricular/atrial cardiac muscle cells how does action potential end?
K+ efflex (repolarization) via potassium channels
What are the symptoms of dysrhythmias?
Palpitations
Dizziness
Fainting
Dyspnea
or asymptomatic sometimes
What is the HR of someone with supraventricular tachycardia?
120-250 beats/min
What are the kinds of supraventricular tachycardia?
Paroxysmal
Persistent
Permanent
Atrial flutter
Atrial fibrillation
What is Paroxysmal supraventricular tachycardia?
Episodic, starts suddenly and returns to normal within ~24 hours
What is Persistent supraventricular tachycardia?
Episodes last longer than 7 days
Usually treatment is needed to return the heart to a normal rhythm
What is Permanent supraventricular tachycardia?
dysrhythmia lasts for more than a year despite medications and other treatments
What is the most common supraventricular tachycardia type?
Atrial fibrillation
What is Ventricular tachycardia (VT)?
problem with ventricular muscle
How long is non-sustained VT?
<30sec
How long is sustained VT?
> 30sec
What do supraventricular dysrythmias affect?
Ventricular contraction rate
-A-V block desireable
What dysrhythmias are more dangerous?
Ventricular are more dangerous than supraventricular
How is the large variety of antidysrhythmic drugs classified?
Vaughan Williams classification
What can allantidysrhythmics cause?
Dysrhythmias
-Create new and/or worsen existing ones
How are drugs classified with Vaughan Williams classification?
Into Class Ia,b,c, Class II, Class III, Class IV and unclassified
What are Class Ia, Ib, Ic antidysrhythmic drugs?
Na Channel blockers
What are Class II antidysrythmic drugs?
beta-blockers
What are Class III antidysrythmic drugs?
K channel blockers (+ others)
What are Class IV antidysrythmic drugs?
Calcium channel blockers
What are unclassified antidysrythmic drugs?
Adenosine, digoxin
What do Class I: Na channel blockers do?
All block Na channels which slows depolarization
Why are Class I: Na channel blockers subdivided?
Because they have differing pharmacological effects
What Na channel blockers are in Class Ia?
Quinidine, procainamide and disopyramide
What do Class Ia: Na channel blockers do?
-Block Na channels
Slows atrial and ventricular rates
Delay repolarization (Class III acgtion)
Increase the AP duration
What are Class Ia: Na channel blockers used for?
Acute onset atrial fibrillation
-Premature atrial contractions (PAC)
-Premature ventricula contractions (PVCs)
-Ventricular tachycardia
-Wolff-Parkinson-White syndrome (cause Tachy, atrial fib/flutter)
What Na channel blockers are in Class Ib?
IV Lidocaine
What do Class Ib: Na channel blockers do?
-Block Na channels
Accelerate repolarization
Decrease AP duration
What are Class Ib: Na channel blockers used for?
Ventricular dysrhythmias only
-PVC
-Ventricular tachycardia
-Fibrillation after MI
What Na channel blockers are in Class Ic?
Flecainide, encainide, propafenone
What do Class Ic: Na channel blockers do?
-Block Na channels
Little effect on AP duration or repolarization
What are Class Ic: Na channel blockers used for?
Severe ventricular dysrhythmias
Atrial fibrillation
What beta-blockers are in Class II?
Metaprolol, esmolol (IV), propanolol, sotalol
What do Class II: Beta-blockers do?
reduce or block sympathetic nervous system stimulation
-AV block
What are Class II: Beta-blockers used for?
Myocardial depressents for supraventricular and ventricular dysrhythmias
What Potassium channel blockers are in Class III?
Amiodarone, dofetilide, sotalol, bretylium
What do Class III: Potassium channe blockers do?
Prolong repolarization
Prolong cardiac AP, extends refractory period of cells
What does Amiodarone also affect?
SA node contractility
What is Amiodarone?
Very effective drug but ~75% have serious adverse effects
-Lung fibrosis, thyroid
How long do you need to use Amiodarone to have serious adverse effects (~75%)?
6 months
What percentage of cases of amiodarone causing adverse effects are fatal?
10%
What is Amiodarone used for?
Ventricular tachycardia
Ventricular fibrillation
Atrial fibrillation
Atrial flutter
-resistant to other drugs
Sustained ventricular tachycardia
What do Class IV: Calcium Channel Blockers do?
Inhibit Ca entry into the cell (Cardio-active)
Act on AV node which reduces conduction velocity
-AV block
What Calcium channel blockers are in Class IV?
Diltiazem, verapamil
What are Class IV: Ca channel blockers used for?
Proxysmal (periodic attack) SVT
Rate control for atrial fib and flutter
NOT for ventricular dysrythmias
What do Unclassified antidysrythmics do (Digoxin and adenosine)?
Decrease AV conduction and SA node automaticity
What does digoxin do?
AV block
Slows heartrate
What does adenosine ddo?
Slows conduction through AV node (AV block)
What is Adenosine used for?
Convert paroxysmal supraventricular tachycardia to sinus rhythm
Describe the hald life of adenosine?
Short
10-20 sec
What is the only way adenosine is administered?
Fast IV push
What may adenosine cause?
Asytole for a few seconds
What should the client know to notify a HCP about when taking antidysrhythmics?
Worsening dysrythmia
Shortness of breath
Edema
Dizziness
Syncope
Signs of toxicity
What should clients taking Beta-blockers or digoxin be taught to how to do?
How to take their own radial pulse for 1 full minute
-Notify physician if pulse is less than 60bpm before taking next dose
What therapeutic response should the nurse monitor for?
Decrease BP in hypertensive clients
Decreased edema
Regular pulse rate
Pulse rate without major irregularities
Improved cardiac output