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Flashcards in Class I antiarrhythmics Deck (14):

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