Antiarrhythmics II

Question 1

what are the class III drugs

Answer 1

AiDS
Amiodarone
ibutilide
Dofetilide
Sotalol

Question 2

mechanism of class III drugs

Answer 2

K channel blockers hence increase QT interval

Question 3

special mechanisms of the class III drugs

Answer 3

• Amiodarone has class I (Na channel blocker), II (beta blocker), class III (K channel blocker), and class IV (calcium channel blocker) activity
• dofetilide has no extracardiac effects
• sotalol is a class III drug in addition to having weak beta blocking activity

Question 4

clinical uses of class III drugs

Answer 4

• amiodarone - severe supraventricular and ventricular arrhythmias, acute VT refractory to cardioversion shock, maintain ventricular rate in a-fib pts
• dofetilide - maintenance of normal sinus rhythm, conversion of a-flutter or a-fib to normal sinus rhythm
• sotalol - life threatening ventricular arrhythmias, maintenance of sinus rhythm in pts with a-fib or a-flutter

Question 5

adverse effects of class III drugs

Answer 5

• amiodarone: interstitial pulmonary fibrosis, hypo or hyper thyroidism, corneal deposits, blue grey skin discoloration, photosensitivity
• dofetilide: possible ventricular tachycardia, torsades de pointes

Question 6

contraindication of class III drugs

Answer 6

• amiodarone can alter effects of digoxin, warfarin, theophylline, and quinidine (DWTQ - dancing with Tom Queen)
• bradycardia, hypotension, SA or AV block, severe respiratory failure

Question 7

what are the class IV drugs

Answer 7

diltiazem and verapamil (antihydropyridines)

calcium channel blockers

Question 8

mechanism of class IV drugs

Answer 8

calcium channel blockers and slows conduction in SA and AV nodes

major effect on cardiac and vascular smooth muscle

Question 9

clinical uses of class IV drugs

Answer 9

• supraventricular tachycardia

- reduction of ventricular rate in a-fib and a-flutter

Question 10

adverse effects of class IV drugs

Answer 10

excessive bradycardia, impaired cardiac conduction, depressed contractility

Question 11

contraindications of class IV drugs

Answer 11

preexisting cardiac depressed function

verapamil increases the conc of simvastatin, lovastatin, digoxin, and dofetilide, (SLiDD)

Question 12

what are the miscellaneous drugs used for antiarrhythmias

Answer 12

MAAD

magnesium, adenosine, atropine, digoxin

Question 13

clinical use of digoxin

Answer 13

control of ventricular response rate in atrial fibrillation and flutter with impaired left ventricular function or heart failure

direct AV node blocking effects and activation of vagomimetic properties

Question 14

adverse effects of digoxin

Answer 14

cardiac arrhythmias esp a-tach and AV block

toxic doses can lead to v-tach and v-fib

Question 15

what is adenosine used for

Answer 15

abolishing acute supraventricular tachycardia

Question 16

mechanism of action of adenosine

Answer 16

• enhances K conductance via G protein
• inhibits cAMP mediated ca2+
• hyperpolarization in AV node

Question 17

adverse effects of adenosine

Answer 17

bronchoconstriction can occur in asthmatic patient for up to 30 mins

Question 18

clinical use of magnesium

Answer 18

• torsades de pointes
• digitalis induced arrhythmia
• prophylaxis of arrhythmia in acute MI

Question 19

mechanism of magnesium

Answer 19

functions as a calcium antagonist by preventing the influx of calcium into the cell

Question 20

what is atropine used for

Answer 20

bradyarrhythmias

Question 21

how is a-fib managed

Answer 21

1. slow down ventricular rate
2. prevent thromboembolism
3. correction of rhythm disturbance

Question 22

first line rate control options for a-fib

Answer 22

class II drugs - beta blockers (PEM - propanalol, esmolol, metapronol)
class IV drugs - diltiazem and verapamil

Question 23

when is amiodarone used in a-fib

Answer 23

• patients who are refractory

- or contraindications to beta blockers, calcium channel blockers, digoxin

Question 24

patients with a-fib for longer than 48 hours or an unknown period should be given what and why

Answer 24

warfarin because a-fib can cause clots due to viscous blood (stasis) and can lead to stroke

Question 25

how long is warfarin given to patient with a-fib

Answer 25

for three weeks prior to cardioversion and up to 4 weeks after effective cardioversion and return of normal sinus rhythm

Question 26

what drug is given to patient with a-fib of less than 48 hours and before when?

Answer 26

heparin and prior to cardioversion (DCC - direct current cardioversion)

Question 27

what are the recommended drugs for conversion of a-fib to normal sinus rhythm

Answer 27

F-PAD

flecainamide, propafenone, amiodarone, dofetilide