Cardiology - Antiarrhythmics Flashcards
What do the Class IA Antiarrhythmics do?
Sodium channel blockade with some K+ channel block
–> decreases speed of depolarisation
And PROLONGS repolarisation
(MOD potency, INTERMEDIATE kinetics)
Three examples of Class IA Antiarrhythmics?
Quinidine
Procainamide
Disopyramide
What do the Class IB Antiarrhythmics do?
Sodium channel blockade
–> decreases speed of depolarisation
And NO CHANGE to repolarisation
(LOW potency, RAPID kinetics)
Three examples of Class IB Antiarrhythmics?
Lidocaine
Mexilitene
Phenytoin
What do Class IC Antiarrhythmics do?
Sodium channel blockade
–> decrease speed of depolarisation
And SHORTENS repolarisation
Also PROLONG REFRACTORY PERIOD
(HIGH potency, SLOW kinetics)
Two examples of Class IC antiarrythmics?
Flecainide
Propaferone
Flecainide is a Class IC Antiarrhythmic, what does it do in addition?
Decreases action potential WITHOUT affecting duration
Propafenone is a Class IC Antiarrhythmic, what does it do in addition?
Reduces spontaneous automaticity
Which Antiarrhythmic Class must be avoided in structural heart disease or coronary artery disease?
Class IC (Flecainide or Propafenone)
What do Class II Antiarrhythmics do?
Beta adrenergic blockade
Decreases SYMPATHETIC TONE
SUPPRESS: automaticity, SA conduction and AV conduction
Name 5 Class II Antiarrhythmics
Metoprolol Propranolol Carvedilol Atenolol Bisoprolol
What do the Class III Antiarrhythmics do?
Block potassium channels
Prolong action potential
Delay repolarisation
Amiodarone is a Class III Antiarrhythmic, what does it do in addition to Class III action?
Class III drugs block potassium channels, prolong action potentials, and delay repolarisation
Amiodarone also blocks Na channels and Ca channels
Side effects of amiodarone?
Thyroid: at any dose! Hypo (6%) and hyper (2%)
Resp: fibrosis in up to 20%
Hepatic: LFT derangement (25%) and cirrhosis (2%)
Eyes: photosensitivity (50%) and corneal deposits (90%)
Dronedarone is a Class III Antiarrhythmic. In addition to class action what does it do?
Class III drugs block potassium channels, prolong action potentials, and delay repolarisation
Dronedarone also is a NEGATIVE INOTROPE by:
- blocking Na channels
- blocking beta1 receptors
- altering adenylyl cyclase generation
Extra benefit:
- reduce hospitalisation in pAF
- reduce stroke (esp if CHADS2>=2)
Sotolol is a Class III Antiarrhythmic. In addition to the Class action what does it do?
Class III drugs block potassium channels, prolong action potentials, and delay repolarisation
It PROLONGS QTc
** sotolol is a mix of d and i isomers.
d-isomer: prolongs repolarisation (Class III effect)
i-isomer: acts as nonselective beta blocker
Ibutilide is a Class III Antiarrhythmic. In addition to class action what does it do?
Class III drugs block potassium channels, prolong action potentials, and delay repolarisation
Also changes atrial cycle length variability
Dofetilide is a Class III Antiarrhythmic. In addition to class action what does it do?
Class III drugs block potassium channels, prolong action potentials, and delay repolarisation
Also terminates INDUCED re-entrant tachycardias
NO IMPACT on Na channels or alpha/beta receptors
NO IMPACT on cardiac output, stroke volume or vascular resistance
Name the five Class III Antiarrhythmics?
Amiodarone Dronedarone Sotolol Ibulitide Dofetilide
What do the Class IV Antiarrhythmics do?
Calcium channel blockade (nonhydropyridine)
Suppression of SA and AV conduction
Name the two Class IV Antiarrhythmics?
Verapamil
Diltiazem
How does Adenosine work?
TRANSIENTLY blocks the ANTEGRADE AV node conduction
How do Cardiac Glycosides work?
Cardiac Glycoside = Digoxin
1) Increases vagal activity, slowing SA and AV nodal conduction
(NOT EFFECTIVE if there is increased sympathetic tone!)
2) Direct and indirect INOTROPE
3) Increases MYOCYTE CONTRACTILITY
4) Indirectly enhances CAROTID SINUS activity and enhances sympathimimetic withdrawal to increased mean arterial pressure
What class of Antiarrhythmic is:
Quinidine
Class IA
What class of Antiarrhythmic is:
Lidocaine
Class IB
What class of Antiarrhythmic is:
Procainamide
Class IA
What class of Antiarrhythmic is:
Propafenone
Class IC
What class of Antiarrhythmic is:
Metoprolol
Class II
What class of Antiarrhythmic is:
Disopyramide
Class IA
What class of Antiarrhythmic is:
Sotolol
Class III
What class of Antiarrhythmic is:
Amiodarone
Class III
What class of Antiarrhythmic is:
Phenytoin
Class IB
What class of Antiarrhythmic is:
Mexilitene
Class IB
What class of Antiarrhythmic is:
Flecainide
Class IC
What class of Antiarrhythmic is:
Bisoprolol
Class II
What class of Antiarrhythmic is:
Dofetilide
Class III
What class of Antiarrhythmic is:
Verapamil
Class IV
What class of Antiarrhythmic is:
Digoxin
Not technically a Class, but it is a Cardiac Glycoside
What class of Antiarrhythmic is:
Dronedarone
Class III
What class of Antiarrhythmic is:
Ibutilide
Class III
How does Atropine work?
When is it used?
What are its effects?
= antagonist to muscarinic acetylcholine receptors
Used in organophosphate poisoning
Effect: tachycardia and mydriasis
