Class I antiarrhythmics Flashcards
What are some commonalities to the functions of class I antiarrhythmics?
the all decrease the slope of phase 0 of the AP and slow conduction. they incr. the threshold for firing in abnormal pacemaker cells.
toxicities are all worsened by hyperkalemia
they are all state dependent (selectively depresses tissue that is frequently activated)
list the class Ia antiarrhythmics
quinidine, procainamide, disopyramide
Mechanism of class Ia antiarrhythmics
decrease the slope of phase 0 and prolong the AP. increase the effective refractory period and increase QT interval.
Use for Class IA antiarrhythmics
atrial and ventricular arrythmias, esp. re-entrant and ectopic SVT and VT
toxicity of class IA antiarrhythmics
procainamide: SLE-like syndrome
cinchonism (headache and tinnits with quinidine), heart failure with disopyramide. all can cause thrombocytopenia, torsades de points
list the class IB antiarrhythmics
lidocaine, mexiletine (phenytoin)
mechanism of the class IB antiarrhythmics
shorten the AP duration. decrease the slope of phase zero. especially effect ischemic or depolarized Purkinje/ventricular tissue
class IB uses
acute ventricular arrhythmias, esp. post-MI. digitalis-induced arrhythmias. (it is the best post-MI)
toxicity of class IB antiarrhythmics
CNS stimulation/depression; CV depression
list class IC antiarrhythmics
Flecainide, propafenone
mechanism of class IC anti-arrhythmics
prolongs the refractory period in the AV node. minimal effects on AP duration
clinical use of class IC anti-arrhythmics
supraventricular tachycardia, including afib. only as a last resort in ventricular tachycardia
toxicity of class IC anti-arrhythmics
proarrhythmic, esp. post-MI. it is contraindicated in structal and ischemic heart disease
When is Mg used as an antiarrhythmic?
torsades de points and digoxin toxicity
