Anti-arrhythmic drugs

Question 1

Tx for increased automaticity

Answer 1

reduce slope of phase 4 depol

prolong refractory period

Question 2

Tx for re-entry circuits

Answer 2

lengthen refractory period

impair impulse propagation in retrograde

Question 3

Class I antiarrhythmic MOA

Answer 3

Na channel blockade

Question 4

Class II antiarrhythmic MOA

Answer 4

beta-adrenergic receptor blockade

Question 5

Class III antiarrhythmic MOA

Answer 5

Prolong AP duration (K channel block)

Question 6

Class IV antiarrhythmic MOA

Answer 6

Ca channel antagonists

Question 7

Digoxin MOA

Answer 7

Positive inotropy , prolong refractory period of AV node
Mechanical: increase contractility
inhibit sarcolemmal Na/K ATPase –> more Ca pumped into sarcolemma

Electric: slow conduction velocity, prolong refractory period of AV node
enhance vagal tone & reduce sympathetic activity

many toxic effects once it reaches toxic range

Question 8

Digoxin indications

Answer 8

HF
a-fib, a-flutter
PSVT

Question 9

Atropine MOA

Answer 9

Anticholinergic - competitively bind to muscarinic, suppress vagal stimulation
transient effect

Question 10

Atropine indications

Answer 10

symptomatic bradycardias
only increases HR acutely, transient effect
pacemakers needed for a sustained action

Question 11

Adenosine MOA

Answer 11

iv adenosine - transient heart block in AV node, decreasing HR
commonly administered to patients with AV node re-entry
binds A1 receptor –> inhibition of adenylyl cyclase –> reduction in cAMP –> hyperpolarization by increased efflux of K

endothelial-dependent relaxation of smooth muscles surrounding arteries

Question 12

Adenosine SEs

Answer 12

facial flushing
temporary rash on the chest
lightheadedness
diaphoresis
nausea
"sense of impending doom"
angina