Antiarrhythmic drugs Flashcards
Impulse propagation depends on –
conduction velocity and gNa+
conduction velocity depends on -
intracellular resistance and gNa+
gNa+ depends on
transmembrane [Na+] gradient and state of Na+ channel readiness
shortest interval at which a premature stimulus results in a propagated response
effective refractory period
sodium channel blockade
quinidine, lidocaine, encainide
beta-adrenergic blockade
propranolol
moderate phase-0 depression and slow conduction (usually long repolarization)
quinidine
minimal phase-0 depression and slow conduction (usually shorten repolarization)
lidocaine
marked phase-0 depression and slow conduction (little effect on repolarization)
encainide
prolong repolarization
amiodarone (and quinidine)
Ca2+ channel blockade
verapamil, diltiazem
adenosine, digitalis glycosides are – drugs
miscellaneous
Class IA antiarrhytmic drugs
quinidine
What does quinidine block (class IA)?
use-dependent block of Na+ channels
Class IA (quinidine) drugs have a similar action on the heart as –
peripheral nerves
Difference between the action of peripheral nerves and Class IA (quinidine) on the heart
Class IA (quinidine) affect the heart at lower concentrations
What treatments are Class IA (quinidine) used for?
prophylaxis
treatment of supraventricular arrhythmia
treatment of ventricle arrhythmia
How can you decrease automaticity?
NT or drugs that increase K+ permeability or decrease Na+/Ca2+ permeability
What causes the pacemaker potential?
net influx of positive charge
How does a large membrane hyperpolarization affect the pacemaker potential?
longer to reach threshold (heart skips a beat)
how can you change the pacemaker potential’s slope?
release Ach decreases slope
release NE increases slope
what does a decreased slope of a pacemaker potential result in?
decreased HR
How is the intensity of inward Na+ current reflected?
in the maximal rate of rise (Vmax) of AP phase-0 (depol)
Effect of larger phase 0
more intense Na+ current –> increase conduction velocity
