Antiarrhythmia

Question 1

What class of antiarrhythmic drugs that work on fast response fibers of the heart (heart muscle)? and what kind of arrhythmia does is treat?

Answer 1

Class I and III—>ventricular arrhythmia (fast response fibers)

Question 2

What class of antiarrhythmic drugs that work on phase 0 and 4 of slow response fibers of SA and AV node?

Answer 2

Class II (beta blockers) and IV (Na channel blockers)

Question 3

What class of antiarrhythmic drugs are used for SVT?

Answer 3

Class II and IV

Question 4

What are all the antiarrhythmic drugs’ affects on EEG?

Answer 4

Class I and III—>prolonged QT (ventricular contraction)

Class II and IV—>prolonged PR (atrial contraction)

Question 5

What are the symp and parasymp’s affect on slow response fiber?

Answer 5

Symp—>increase the slope of phase 0 and 4

Paraymp—>decrease the slope of phase 0 and 4

Question 6

Vagal stimulation is useful for ventricular or supraventricular tachy?

Answer 6

SVT

Question 7

Why is SA node the pacemaker of the heart?

Answer 7

Is has the fastest phase 4 (repolarization)

Question 8

What else does K channel blocker prolong besides repolarization?

Answer 8

Effective refractory period (ERP) and action potential duration (APD)

Question 9

How does the sodium channel change from the beginning to late phase 3? what is the resting state of sodium channel?

Answer 9

Beginning of phase 0—>M and h gate open (active state)
Late phase 0 to phase 3—>h gate closes (inactive state)
Then back to resting state—>M gate closes and h gate open

Question 10

What state of the sodium channel does class I antiarrhythmic drug target?

Answer 10

Active and inactive state—>mainly inactive state

Question 11

What are the characteristics of class Ia Ib and Ic drugs?

Answer 11

Ia–>block both Na and K channels—>prolonged QT—>torsades
Ib—>block Na channel in ischemic tissues of the heart/shorten APD
Ic—>proarrhythmia/use for SVT like a fib

Question 12

Why don’t we use quinidine much anymore? and what enhance the toxicity of it?

Answer 12

It also blocks muscarinic receptor at heart—>increase HR
It blocks alpha 1—>vasodilate—>reflex tachy
Cinchonism—>GI upset and tinnitus
Hyperkalemia

Question 13

What are the class Ia Ib and Ic drugs? Double quarter pounder/lettuce tomato mayo/more fries please

Answer 13

Ia—>disopyramide/quinidine/procainamide
Ib—>lidocaine/mexiletine
Ic—>moricizine/flecainide/propafenone

Question 14

What causes torsades?

Answer 14

Drugs that block K channel—>prolonged QT

Question 15

What are lidocaine and mexiletine used for?

Answer 15

Ventricular arrhythmia or tachy (post MI)
Digoxin induced ventricular arrhythmia
Mexiletine—>oral lidocaine

Question 16

Which beta blocker is used IV for acute SVT?

Answer 16

Esmolol

Question 17

What is the antiarrhythmic drug that treats all arrhythmia? and what are its side effects?

Answer 17

Amiodarone (contain iodine)

Pul fibrosis/blue skin/hypo or hyperthyroidism/hepatic necrosis

Question 18

What else does sotalol block besides K channel?

Answer 18

Beta blocker

Question 19

What is torsades de pointes? what class cause it? and what is the drug that most likely cause torsades? and how do we treat it?

Answer 19

QT prolongation—>ventricular tachy
Class I and III
Sotalol
Give Mg

Question 20

What drugs should Long QT syndrome pt avoid?

Answer 20

Class I and III

Question 21

What are the class III and IV drugs?

Answer 21

Class III—>amiodarone/sotalol/dofetilide/ibutilide

Class IV—>verapamil/diltiazam

Question 22

What are the side effect of class IV and what drug interaction are there?

Answer 22

Verapamil—>constipation
AV block—>worsen with beta blocker or digoxin
Verapamil and quinidine displace digoxin

Question 23

What is adenosine used for?

Answer 23

Work on adenosine receptor
SVT (DOC for PSVT)
Short half life—>not for chronic

Question 24

What else can be used to treat PSVT besides adenosine?

Answer 24

Class II and IV (for SVT)

Carotid sinus massage/valsalva—>stimulate vagal

Question 25

What other drugs can cause torsades?

Answer 25

Thioridazine/TCA

Question 26

SUMMARY

Drugs that treat SVT and VT?

Answer 26

SVT:
class II and IV/adenosine/digoxin
VT:
class I and III

Question 27

How to treat a fib?

Answer 27

Class II and IV for rate control + anticoagulant

Flecainide for rhythm control