17 Mechanisms of anti-arrhythmic drugs Flashcards
mechanisms of propagation blocks
- *more positive resting membrane potential**
- less Na channels activated/slower conduction velocity/higher threshold
ischemia = decreased ATP
- Katp channels open/raised threshold/time from stimulus to phase 0 increased
3 conditions for re-entry to occur
2 parallel conduction paths
unidirectional block in one path(extended refractoriness)
slow or delayed conduction in other path
relavent class IA antiarrhythmics
mechanism, effect, use
”
quinidine, procainamid, disopyramide
block Na channels
increase length of AP, ERP and QT
procainamide is used acutely
“
class IB antiarrhythmic drugs
mechanism, effect, use
“lidocaine
blocks Na channels
decrease length of AP
acute ventricular arrhythmias
”
class IC antiarrhythmic drugs
mechanism
“flecainide, propafenone
strongly depress Na current(rate of rise of AP) strongly
“
class II antiarrhythmic drugs
b-blockers
Propanolol(B1/2)
metoprolol, esmolol, atenolol (all B1 specific)
Carvedilol - B1/2/a1
Labetalol - B1/2/a
Reduced excitability and decreased conduction velocity in AV node
class III antiarrythmic drugs
mechanism? effect?
amiodarone, dronedarone, sotalol, ibutilide, dofetilide
K+ channel blocker; prolong AP duration
“describe ““reverse use dependence”” and which drug class these applyt o”
“K channel blockers work BEST when the channels are in resting state
therefore, these drugs produce long QT better at lower HRs
this is the opposite of ""use-dependent"" Na channel blockers(class I) "
class IV antiarrhythmic drugs
mechanism? effect?
verapamil, diltiazem
CCBs
increase refractoriness in AV node; harder for SA/AV to depolarize
digoxin
Na-K exchange pump inhibitor
M2 agonist - vagal input activation
shortes refractory period; can be bad if there are aberrant pathways(enhanced excitability)
antiarrhythmic drugs crossing the BBB; effect?
lidocaine - seizures
propanolol - nightmares, sedation
digoxin - cognitive/vision effects
metoprolol?
adverse effects of amiodarone
high iodine content - propensity to cause hyper/hypothyroidism
pulmonary fibrosis
blue skin
photosensitivity
corneal deposits
drug treatment for atrial flutter or afib
BBs or CCBs to slow AV excitability
anticoagulate if longer than 48 hrs
add class III drug to return to normal sinus rhythm
difference between atrial fibrillation and flutter
flutter - excessive p waves; consistant/regugular QRS beats
fibrillation - irregularly irregular; QRS are not rhythmic; p waves are excessive/sporadic
AVNRT treatment
difference for AVRT treatment?
- *acute**
- vagal maneuvers
- adenosine(IV) most effective; possibly verapamil to slow conduction/reentry
long term
- BBs or CCBs
- ablation
avoid CCBs and digoxin for AVRT since it can increase conduction down aberrant pathways(refractoriness is reduced on CCBs); otherwise, treatment is the same