Anti-Arrhythmia Drugs Flashcards
3 mechanisms for drugs to be anti-arrhythmic
decrease autmaticity
increase refractory period
decrease conduction velocity
what are the five ways to decrease automaticity of a cell?
- increase threshold potential
- decrease phase 4 slope
- increase AP duration
- slow SA/AV node depolarization
- increase maximum diastolic potential
mechanism to increase the depolarization threshold and class of these drugs
block sodium channels
class 1 anti arrhythmics
what are the subsets of class I antiarrhythmics and which of these also blocks potassium channels?
A,B,C
Class IA blocks potassium too
rate class IA-C by increasing strength of Na block
B is weakest
A in the middle
C is strongest
with potassium channel blocking…what is the greatest toxicity?
will lead to lengthened QT…so torsades
name the class IA anti-arrhythmic and its function
Procainamide…Na and K blockers
name the two class IC anti-arrhythmics and its function
Flecainide and Propafenone..Na blockers
what is the warning with class IC drugs?
do not give to patients with structural heart abnormalities
name the class IB anti arrhythmic and its function
lidocaine and Na blocker
how do we decrease the phase 4 slope in the action potential of a nodal cell?
block the HCN channels
what common drugs block the HCN channels?
beta antagonists
class II anti-arrhythmics are what type of drug?
beta blockers
how to increase length of the action potential?
block the K channels that are repolarizing the cells
what class of antiarrhythmics block the K channels to lengthen the action potentials?
Class III and Class IA
name the Class II anti arrhythmics to know
metoprolol, propanolol, atenolol, carvedilol
how to slow depolarization of SA/AV node cells?
block calcium channels
what class of anti arrhythmics blocks calcium channels?
class IV
what are the two calcium channel blockers of class IV to know for cardiac muscle?
verapamil and diltiazem
what other effect can calcium channel blockers have?
decrease smooth muscle tone so they can treat hypertension
how do we increase the maximum diastolic potential and what does this actually mean?
the repolarization drops lower…do this via stimulating K+ influx to the cell
what is the drug that does a good job at increasing the maximum diastolic potential?
adenosine brings in more K+
how must we administer adenosine and why?
IV bolus because its naturally occurring and has receptors all over so need it to get to the heart fast
name the two classes of drugs that will cause the AP to lengthen
class IA class III BOTH POTASSIUM BLOCKERS
name the four classes of drugs that will slow recovery of Na channels
class IA,B,C adenosine
name the four classes of drugs that will slow recovery of Na channels or Ca channels
class IA,B,C adenosine is Ca channels
the class IABC and adenosine all slow recovery of the Na channels…what is the effect this has on the AP?
the AP will not be lengthened like it is with potassium block…rather the recovery of the Na channels just takes longer and causes the cells to be refractory
three mechanisms to slow conduction velocity through the AV node
block Ca channels
block HCN channels
increase K+ influx
what three classes/drugs can be nodal (AV) blockers?
class II (HCN) IV (Ca) and adenosine (K+)
name the four class III anti arrhythmics
amiodarone, dronedarone, dofetalide, sotalol
