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Cardiology > Pharmacology: Drugs Affecting Cardiac Rhythm I and II > Flashcards

Pharmacology: Drugs Affecting Cardiac Rhythm I and II Flashcards

1
Q

8 prototypical antiarrhythmic drugs per Singh-Vaughan Williams

A

procainamide, lidocaine, flecainide, atenolol, dofetilide, verapamil, digoxin, adenosine

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2
Q

What are targets of Class IA antiarrhythmics and what is the prototypical example of such a drug?

A

Na, K currents –> procainamide

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3
Q

What are targets of Class IB antiarrhythmics and what is the prototypical example of such a drug?

A

Na current –> lidocaine

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4
Q

What are targets of Class IC antiarrhythmics and what is the prototypical example of such a drug?

A

Na current –> flecainide

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5
Q

What are targets of Class II antiarrhythmics and what is the prototypical example of such a drug?

A

beta blockers –> beta receptor –> Ca, K, F currents –> atenolol

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6
Q

What are targets of Class III antiarrhythmics and what is the prototypical example of such a drug?

A

K current –> dofelitide

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7
Q

What are targets of Class IV antiarrhythmics and what is the prototypical example of such a drug?

A

calcium channel blockers –> Ca current –> verapamil

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8
Q

What is adenosine’s target?

A

P/purinergic - adenosine receptor

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9
Q

Drugs used to treat v-tach

A

Class I and III

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10
Q

Drugs used to treat a-fib

A

Class I and III

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11
Q

Drugs used to treat AV reentry

A

Class I and II and III

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12
Q

Drugs used to treat AV nodal reentry

A

Class II and IV and digoxin and adenosine

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13
Q

What are the drug effects that treat reentrant tachycardias?

A

reduced excitability (except class III), slower conduction velocity (except class III), longer refractory period (except class IB), IA and III increase AP duration

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14
Q

What are the drug effects that treat automaticity?

A

slow down phase 4 depolarization

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15
Q

What are the drug effects that treat tachycardia due to early afterdepolarization (e.g. torsades de pointes)

A

prolong ventricular action potential duration

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16
Q

Potency of Class I drugs

A
  1. C>A>B
  2. more potent at fast heart rate
  3. more potent at depolarized resting membrane potential
17
Q

What factors increase the effect of K current blockade on AP duration? (which drugs do this?)

A

Class IA and III –>

  1. slow heart rate
  2. low extracellular K
  3. low extracellular Mg
18
Q

What are parasympathetic effects on heart as modulated by digoxin?

A

reduction in beta-receptor mediated calcium current and increase in muscarinic K current –> more depolarization

19
Q

What are effects on heart as modulated by adenosine?

A

reduction in beta-receptor mediated calcium current and increase in muscarinic K current –> more depolarization

20
Q

What are the effects of Class II, IV, digoxin, and adenosine on sinus rate, AVN ERP, AVN excitability?

A

reduce sinus rate, increase refractory period, reduce excitability

21
Q

Which calcium channel blockers selective for cardiac and vascular channels?

A 
verapamil = cardiac
nifedipine = vascular
diltiazem = both
22
Q

How do Class II, IV, digoxin, adenosine affect inotropy?

A

digoxin is positive, the others are negative

23
Q

3 requirements for reentry

A
  1. potential path
  2. unidirectional block
  3. slow conduction
24
Q

What is the risk of trying to kill a reentry circuit by causing refractory block –> letting it run into itself?

A

excessively long APD and torsades de pointes

–> require short excitable gap to work

25
Q

What is the risk of trying to reduce a reentry circuit by causing fixed block –> slowing it down?

A

slow conduction facilitates reentry

–> require low safety factor for this to work

26
Q

What is electrical wavelength?

A

the distance traveled by a wavefront during the time between depolarization and end of refractory period of start of wave –> ERP * conduction velocity

27
Q

Do smaller wavelengths promote or protect against afib?

28
Q

Drugs that affect cardiac rhythm that are used for nonarrhythmic indications: htn

A

ca blockers, beta blockers

29
Q

Drugs that affect cardiac rhythm that are used for nonarrhythmic indications: systolic dysfunction

A

beta blockers, digoxin

30
Q

Drugs that affect cardiac rhythm that are used for nonarrhythmic indications: ischemia

A

ca blockers, beta blockers

31
Q

Risk of antiarrhythmics in pts with long qt, low K, low Mg

A

torsade de pointes w/ class IA, III

32
Q

Risk of antiarrhythmics in pts with sick sinus

A

worse sinus bradycardia w/ class II, IV, digoxin, amiodarone

33
Q

Risk of antiarrhythmics in pts with AV block

A

higher degree AV block w/ class II, IV, slowed junctional pacers w/ class I, II

34
Q

Risk of antiarrhythmics in pts with poor systolic function

A

Class I, II, IV are negatively inotropic

Cardiology (41 decks)

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