Antiarrhythmics

Question 1

Arrhythmias: Basic causes?

Answer 1

disturbance of impulse formation/conduction

Question 2

Arrhythmias: Precipitating factors?

Answer 2

ischemia/hypoxia
pH Δs
high catecholamines
drug tox (digitalis, antiarrhy)
overstretch
injured/dz tissue

Question 3

Impulse conduction disturbances caused by?

Answer 3

Simple block:
AV node, bundle branch

Reentry (major):
conduction block, unidirectional block, long conduction time

Question 4

Normal impulse conduction?

Answer 4

two impulses extinguish each other ->

allows channels to reset

Question 5

Unidirectional block/Reentry????

Answer 5

slide 12???

Question 6

Goal of arrhythmia therapy?

Answer 6

↓ ectopic (abn place) pacemaker activity

Question 7

Antiarrhy at regular dose suppresses?

Answer 7

ectopic auto
abn conduction
min effect on normal cells

Question 8

Antiarrhy at high doses do what?

Answer 8

depress conduction in normal tissue,

produce arrhythmias

Question 9

Class I Antiarrhy action?

Answer 9

block Na+ channels

Question 10

Class IA Antiarrhy action?

Answer 10

block open or activated Na+ channel ->

lengthens AP

Question 11

Class IB Antiarrhy action?

Answer 11

block inactivated Na+ channel ->

shorten AP

Question 12

Class IC Antiarrhy action?

Answer 12

binds all Na+ channels ->

Φ effect on AP

Question 13

Class II Antiarrhy action?

Answer 13

↓ adrenergic activity on heart

Question 14

Class III Antiarrhy action?

Answer 14

inhibit K+ channel -> lengthen AP

Question 15

Class IV Antiarrhy action?

Answer 15

block Ca2+ channel -> ↓ HR and contract

Question 16

Torsade de pointes is?

Answer 16

rapid, unstable vent tachy:

EKG = polymorphic tachy w/ single normal sinus beat, followed by long QT, immediate return to poly tachy