antiarrhythmic Drugs Flashcards
What 2 classes of drugs are used to lower rate ?
class II: beta-blockers
class IV: Ca2+ blockers
What 2 classes of drugs are used to correct rhythm?
class I: Na+ channel blocker
class III: K+ channel blocker
Class I drug name + specifics
Class I : Na+ channel blocker
Ex: flecanide, lidocaine, propaferode
Class II drug name + specific
Class II: Beta blocker
Ex: metoprolol, etc.
Class III drug name + specific
Class III: K+ channel blocker
Ex: amiodarone, sotalol
Class IV drug name + specific
Class IV: Ca2+ channel blocker
verapamil, dilitazem
How do class I drugs work broadly?
Na+ blockers that prevent phase 0 upstroke
How do class II drugs work broadly?
prevent B1 which decreases contractility and lowers HR
How do class III drugs work broadly?
K+ channel blocker that prevents repolarization
How do class IV drugs work broadly?
Ca2+ channel blocker
decreases the plateau phase (myocyte) or upstroke phase (SA/AV)
This drug is suppresses spontaneous depolarization of SA and AV node via A1 receptor and is helpful in breaking and diagnosing a re-entry SVT.
adenosine
What receptor does adenosine work on?
a1
Which drug blocks Na/ATPase? What is its result?
Digoxin
Increases intracellular Ca2+ which increases LV contractility
What class III agent is iodinated and can lead to hypothyroidism?
amiodarone
Class IB agent gist and example
Blocks Na+ only channels which shortens the QT interval
ex: lidocaine
Class 1A drug that has associated lupus-like syndrome
Procainamide
How do sodium channel blockers work?
phase 0 of myocyte normally has Na+ entering the cell to depolarize it
if we block the sodium channel, the cell cannot depolarize and rhythm will be interrupted
What type of rhythm control is better to treat re-entry tachycardia?
class I
Na+ channels are not in the NA/AV action potential so this won’t slow the AV node which could be a problem in re-entry tachy
What is normally first line treatment for PSVT?
valsalva
then, adenosine
How do valsalva maneuvers work?
they decrease preload due to increased pressure
baroreceptor will compensate for increase in pressure by slowing heart rate
How do K+ channel blockers work?
normally potassium flows out of cell during repolarization
cell will struggle to repolarize if K+ channels are blocked
leads to increased action potential period and refractory period
What 2 phases does calcium channels work on?
1) phase 2 of myocytes
2) phase 0 of AV/SA
Phase 2 effects of class 4 drugs
contraction normally occurs during the plateau
decreased plateau time = decreased contraction
Phase 0 effects of class 4 drugs
prevents depolarization in SA/AV cells
What are 2 effects of digoxin?
1) Increase contractility (by blocking Na+/ATPase you have more intracellular calcium which will lead to an influx of Ca2+)
2) Decrease heart rate through stimulating the parasympathetic system
