Antiarrhythmics

Question 1

Phase 0 of action potential

Answer 1

• rapid depolarization
• Na channels open, increased Na+
• ventricular contraction
• inactive when +65 mV

Question 2

Phase 1 action potential

Answer 2

• early rapid repolarization
• Na permeability is inactivated
• K+ channels open (K efflux)

Question 3

Phase 2 of action potential

Answer 3

• plateau phase
• repolarization, increase in Ca++ through slow channels
• K channels open and maintain plateau

Question 4

Phase 3 of action potential

Answer 4

• rapid repolarization
• inactivation of Ca and increase in K permeability

Question 5

Phase 4 of action potential

Answer 5

• spontaneous depolarization
• ion balance restored by ATP pumps

Question 6

what channels do antiarrhythmic drugs work on for atria and ventricles?

Answer 6

• Na channels

Question 7

what channels do antiarrhythmic drugs work on for SA and AV node?

Answer 7

Ca++ channels

Question 8

what do Na channel blockers do and what type are they?

Answer 8

• slow the conduction and prolong the QRS complexes in the atria and ventricles
• type 1

Question 9

what do Ca++ channel blockers do and what type are they

Answer 9

• slow the atrial rate (SA node effect) and slow conduction through the AV node (prolong the PR interval)
• type IV

Question 10

what do K channel blockers do and what type are they?

Answer 10

• interrupt reentry by slowing conduction or increasing the refractory period
• prolongs the QT interval and induces triggered activity in the ventricle causing polymorphic VT
• type III

Question 11

class 1 antiarrhythmics inhibit what channels and phase

Answer 11

• inhibits fast Na channels
• affect phase 0
• decreases depolarization rate and conduction velocity

Question 12

class 1A antiarrhythmic drugs

Answer 12

• quinidine
• procainamide
• disopyramide
• moricizone

Question 13

class 1B antiarrhythmic drugs

Answer 13

• lidocaine
• mexilitine

Question 14

class 1C antiarrhythmics drugs

Answer 14

• flecainide
• propafenone

Question 15

class II antiarrhythmics and what they do

Answer 15

• decrease the rate of depolarization
• beta blockers

Question 16

class III antiarrhythmics inhibit what channels

Answer 16

• K channels

Question 17

class III antiarrhythmics (drugs)

Answer 17

• amiodarone
• sotalol
• ibutilide
• dofetilide
• bretylium

Question 18

class IV antiarrhythmics affect what channels

Answer 18

• inhibit slow Ca channels

Question 19

class IV antiarrhythmics (drugs)

Answer 19

• diltiazem
• verapamil

Question 20

action of class 1A drugs

Answer 20

• lengthen the action potential duration and effective refractory period and lengthen repolarization

Question 21

action of class 1B drugs

Answer 21

• less powerful Na channel blockers
• shorten the action potential duration and refractory period in normal cardiac ventricular muscle

Question 22

class 1C action

Answer 22

• Na channel blockers
• decrease the rate of phase 0 and speeds cardiac conduction
• shortens DOA of action potentials in purkinje fibers but ventricular myocardial cells

Question 23

class II beta blockers action

Answer 23

• decrease rate of phase 4
• slow HR
• slows conduction if impulses through atria (prolong P-R)

Question 24

class III action

Answer 24

• block K+
• prolong repolarization

Question 25

class IV

Answer 25

• calcium channel blockers
• inhibit slow Ca++ currents
• verapamil, diltiazem

Question 26

procainamide

Answer 26

• Na and K blocker
• depresses automaticity by decreasing phase 0
• for ventricular tachydysrhythmias and atrial tachycardia

Question 27

procainamide toxicity signs and symptoms

Answer 27

• myocardial depression
• hypotension
• QRS and QT prolongation
• heart block
• SLE like symptoms with chronic admin

Question 28

metabolite of procainamide

Answer 28

• N-acetyl procainamide (NAPA)

Question 29

quinidine

Answer 29

• class 1A
• increase threshold for excitability
• for a-flutter, a-fib, v-tach, v-fib

Question 30

quinidine toxicity

Answer 30

• QT prolongation
• v-tach
• loose stools
• thrombocytopenia
• cinchonism

Question 31

disopyramide

Answer 31

• class 1A
• for atrial tach and ventricular tachyarrhythmias
• known to cause cardiac arrest

Question 32

lidocaine

Answer 32

• Na channel blocker, decrease phase 0
• for ventricular arrythmias, particularly reentry
• ineffective against SVT
• almost no effect on QT

Question 33

early signs of lidocaine toxicity

Answer 33

• nystagmus
• speech changes
  (CNS depression to seizures)

Question 34

phenytoin

Answer 34

• Na channel blocker, depress phase 0
• useful in suppression of ventricular associated with digitalis toxicity
• useful in v-tach or torsades (prolonged QT)

Question 35

phenytoin toxicity

Answer 35

• rapid admin associated with respiratory arrest, hypotension, ectopy, and death
• CNS: drowsiness, nystagmus, nausea, vertigo

Question 36

flecainide (1C)

Answer 36

• blocks Na, K, Ca
• depresses phase 0
• prolongs QRS less than PR
• indicated for suppressing PVCs and atrial tachydysrhythmias including WPW
• moderate inotrope (no CAD, LV failure, v-tach)

Question 37

beta blockers

Answer 37

• slow S-A node (phase 4)
• control SVT
• toxicity can cause bronchospasm