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24 Cards in this Set

  • Front
  • Back
Name the Class IA antiarrhythmics
Name the Class IB antiarrhythmics
Name the Class IC antiarrhythmics
In general, how does a Class I antiarrhythmic change a myocyte's depolarization?
Blocks Na+ channels. This results in a decreased Phase 0 slope and increased threshold for firing.
How does the myocyte's depolarization change with Class IA antiarrhythmics?
Decreases phase 0 slope (some)
Prolonged action potential
(block K+ channels too!)
Long effective refractory period and QT interval
How does the myocyte's depolarization change with Class IB antiarrhythmics?
Decreases phase 0 slope (a little)
Shortened action potential
How does the myocyte's depolarization change with Class IC antiarrhythmics?
Decreases phase 0 slope (a lot)
No change in action potential
What are Class IA antiarrhythmics used for?
Effective in atria and ventricles
Reentrant and ectopic SVT
What are Class IB antiarrhythmics used for?
Best post-MI!

Preferentially affect ischemic or depolarized Purkinje or ventricular tissue
Useful for acute ventricular arrhythmias (especially post-MI) and in digitalis-induced arrhythmias.
What are Class IC antiarrhythmics used for?
Worst post-MI!

Can only be used in patients without structural abnormalities
Last resort in refractory tachyarrhythmias
How do Class II antiarrhythmics have their effects?
Work best on AV node and on cells with automaticity

Suppress abnormal pacemakers by decreasing the slope of phase 4

Slowed conduction through the AV node can cause an increased PR interval
Name the Class III antiarrhythmics?
K - (potassium)
I - Ibutilide
S - Sotalol
B - Bretylium
A - Amiodarone
D - Dofetilide
What is the mechanism of Class III antiarrhythmic's action?
Block the K+ channels, delaying repolarization.
Increases action potential duration, effective refractory period, and QT interval
Amiodarone is a class III antiarrhythmic. How does it work?
Blocks K+ channels... AND...
alters the lipid membrane, leading to class I, II, III, and IV effects.
What must be done when a patient is started on Amiodarone?
Check PFTs, LFTs, and TFTs regularly
What are the side effects of Amiodarone?
Pulmonary fibrosis
Corneal and skin deposits
Cardiovascular effects (bradycardia, CHF, heart block)
Name the Class IV antiarrhythmics

What cells do Class IV antiarrhythmics work on?
AV node and cells with automaticity

Most selective for rapidly depolarizing myocytes in the nodes/atria
How is a myocyte affected by a Class IV antiarrhythmic?
Decreased conductance velocity
Increased PR interval
Increased effective refractory period
What are Class IV antiarrhythmics used for?
Prevention of nodal arrhythmias
How does adenosine work?
Opens K+ channels, which hyperpolarizes the cell and inhibits Ca2+ influx at the SA and AV nodes.
What is adenosine used for?
Termination of supraventricular tachycardia
What drug are the effects of adenosine blocked by?
Theophylline (asthma drug)
When is Mg2+ used with arrhythmias?
Effective against torsades and digoxin toxicity