17 Mechanisms of anti-arrhythmic drugs Flashcards

1
Q

mechanisms of propagation blocks

A
  • *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
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2
Q

3 conditions for re-entry to occur

A

2 parallel conduction paths

unidirectional block in one path(extended refractoriness)

slow or delayed conduction in other path

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3
Q

relavent class IA antiarrhythmics

mechanism, effect, use

A

quinidine, procainamid, disopyramide

block Na channels

increase length of AP, ERP and QT

procainamide is used acutely

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4
Q

class IB antiarrhythmic drugs

mechanism, effect, use

A

lidocaine

blocks Na channels

decrease length of AP

acute ventricular arrhythmias

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5
Q

class IC antiarrhythmic drugs

mechanism

A

flecainide, propafenone

strongly depress Na current(rate of rise of AP) strongly

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6
Q

class II antiarrhythmic drugs

A

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

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7
Q

class III antiarrythmic drugs

mechanism? effect?

A

amiodarone, dronedarone, sotalol, ibutilide, dofetilide

K+ channel blocker; prolong AP duration

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8
Q

“describe ““reverse use dependence”” and which drug class these applyt o”

A

“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)
"
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9
Q

class IV antiarrhythmic drugs

mechanism? effect?

A

verapamil, diltiazem

CCBs

increase refractoriness in AV node; harder for SA/AV to depolarize

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10
Q

digoxin

A

Na-K exchange pump inhibitor

M2 agonist - vagal input activation

shortes refractory period; can be bad if there are aberrant pathways(enhanced excitability)

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11
Q

antiarrhythmic drugs crossing the BBB; effect?

A

lidocaine - seizures

propanolol - nightmares, sedation

digoxin - cognitive/vision effects

metoprolol?

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12
Q

adverse effects of amiodarone

A

high iodine content - propensity to cause hyper/hypothyroidism

pulmonary fibrosis

blue skin

photosensitivity

corneal deposits

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13
Q

drug treatment for atrial flutter or afib

A

BBs or CCBs to slow AV excitability

anticoagulate if longer than 48 hrs

add class III drug to return to normal sinus rhythm

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14
Q

difference between atrial fibrillation and flutter

A

flutter - excessive p waves; consistant/regugular QRS beats

fibrillation - irregularly irregular; QRS are not rhythmic; p waves are excessive/sporadic

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15
Q

AVNRT treatment

difference for AVRT treatment?

A
  • *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

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16
Q

adverse effects of type III antiarrhythmics

A

tend to cause torsades at lower HRs