Various Antiarrhythmic Drugs.

Question 1

INa

Fast AP?

Answer 1

o Responsible for Phase 0

o Rapid depolarization

Question 2

IKs and IKr

Fast AP?

Answer 2

o Open during Phase 2
o Increasing activation in Phase 3
o Allows for maintenance of potential during plateau and repolarization

Question 3

ICa-­‐L

Fast AP?

Answer 3

o Open during Phase 2
o Almost equivalent flow as K allows membrane potential to be constant
o Ca triggers contraction, inactivation allows Phase 3

Question 4

INa

slow AP?

Answer 4

Very little present

Question 5

IKs and IKr

slow AP?

Answer 5

Responsible for Phase 3 (repolarization)

Question 6

ICa-­‐L

slow AP?

Answer 6

Responsible for Phase 0 (slow upstroke)

Question 7

Class Ia Na+ Channel blockers

Which potentials?

Answer 7

Fast > slow

Question 8

Class Ib Na+ channel blockers

Which potentials?

Answer 8

Fast > slow

Question 9

Class Ic Na+ channel blockers

Which potentials?

Answer 9

Fast > slow

Question 10

Class Ia Na+ Channel blockers

Fast AP?

Answer 10

o	Slows Phase 0 (class I effect)
o	Prolongs Phase 2 (class III effect – K channels)
o	Increase refractory period

Question 11

Class Ib Na+ channel blockers

Fast AP?

Answer 11

o Slow Phase 0
o Do not prolong phase 2
o Increase refractory period

Question 12

Class Ic Na+ channel blockers

Fast AP?

Answer 12

o Slow Phase 0
o Mildly prolong phase 2
o Power prolongation of refractory period

Question 13

Class II β blockers

Which potentials?

Answer 13

Unspecified – Used in AV node re-entry arrhythmias and in controlling ventricular rate in A-Fib

Question 14

Class II β blockers

Fast AP?

Answer 14

o Reduce the funny current, ICa-L, and the IKs
o Result = reduced rate of diastolic repolarization
o The pace rate is reduced and the refractory period is prolonged

Question 15

Class II β blockers

Slow AP?

Answer 15

o Reduce the funny current, ICa-L, and the IKs
o Result = reduced rate of diastolic repolarization
o The pace rate is reduced and the refractory period is prolonged

Question 16

Class III K+ channel blockers

Which potentials?

Answer 16

Fast

Question 17

Class III K+ channel blockers

Fast AP?

Answer 17

o Prolongs phase 2 and refractory periods

o Some drugs reduce conduction velocity by blocking Na channels

Question 18

Class IV Ca2+ channel blockers

Which potentials?

Answer 18

Slow (nodal cells) > fast

Question 19

Class IV Ca2+ channel blockers

slow AP?

Answer 19

o Slows the Ca-dependent upstroke
o Slows conduction velocity
o Prolong refractory period

Question 20

Adenosine

Which potentials?

Answer 20

Slow (nodal cells)

Question 21

Adenosine

slow AP?

Answer 21

o Increases K current and decreases Ca current
o Reduces SA and AV node firing rate
o Reduced conduction rate at AV node