Antiarrythmics

Question 1

What are Class I antiarrhythmics?

Answer 1

sodium channel blockers

Question 2

What are Class II antiarrhythmics?

Answer 2

beta blockers

Question 3

What are Class III antiarrhythmics?

Answer 3

potassium channel blockers

Question 4

What are Class IV antiarrhythmics?

Answer 4

calcium channel blockers

Question 5

What are two other antiarrhythmics?

Answer 5

Adenosine and Magnesium.

Question 6

What are the Class IA antiarrythmics?

Answer 6

Quinidine, Procainamide, Disopyramide

Question 7

What is the mechanism of action of Class IA antiarrhythmics?

Answer 7

Slows conduction velocity in atria and his/purkinje fibers. Increases AP duration, increases effection refractory period. Increases QT interval.

Question 8

What are the clinical uses for Class IA anti-arryhthmics?

Answer 8

Useful for atrial and ventricular arryhthmias, especially reentrant and ectopic SVT and VT; depresses automaticity of ectopic foci

Question 9

What are the important toxicities of Class IA antiarrythmics? What is one important toxicity associated iwth each one.

Answer 9

Torsades (long QT), thrombocytopenia.
Quinidine: Cinchonism (headache, tinnitus)
Procainamide: Reversible SLE-like syndrome
Disopyramide: heart failure

Question 10

What are the Class IB antiarrythmics?

Answer 10

Lidocaine, Mexilitine

Question 11

What is the mechanism of action of Class IB antiarrythmics?

Answer 11

 Decreases AP duration; increases conduction velocity of AV node/his-purk. Preferentially affect ischemic or
depolarized Purkinje and ventricular tissue.
Phenytoin can also fall into the IB category.

Question 12

What is the clinical uses of Class IB antiarrhythmics?

Answer 12

Acute ventricular arrhythmias (especially postMI), digitalis-induced arrhythmias. IB is Best
post-MI.

Question 13

What are toxicities associated with Class IB antiarrhythmics?

Answer 13

CNS stimulation/depression, cardiovascular

depression.

Question 14

What are the Class IC antiarrhythmics?

Answer 14

Flecainide, Propafenone.

Question 15

What is the mechanism of action of Class IC antiarrythmics?

Answer 15

Significantly prolongs ERP in AV node and
accessory bypass tracts. No effect on ERP in
Purkinje and ventricular tissue.
Minimal effect on AP duration.

Question 16

What is the clinical uses of Class IC antiarrhythmics?

Answer 16

SVTs, including atrial fibrillation. Only as a last

resort in refractory VT.

Question 17

What are toxicities associated with Class IC antiarrhythmics?

Answer 17

Proarrhythmic, especially post-MI
(contraindicated). IC is Contraindicated in
structural and ischemic heart disease.

Question 18

How do Class II antiarrhythmics work?

Answer 18

Beta blockers. Decreased beta receptor activation, decreased cAMP, decreased Ca2+ current. Thereby decrease SA and AV nodal activity.

Question 19

How do Class II antiarrhythmics affect the slope of phase 4 in pacemaker cells?

Answer 19

Decrease the slope; it takes longer to reach threshold. Suppress abnormal pacemakers.

Question 20

Why does the PR interval increase with Class II antiarrhythmics?

Answer 20

The AV node is particularly sensitive.

Question 21

Which Class 2 antiarryh is shortest acting?

Answer 21

esmolol

Question 22

What are the clinical uses for class II antiarrhythmics?

Answer 22

SVT, ventricular rate control for atrial fibrillation and atrial flutter.

Question 23

What is the toxicity associated with Class 2s?

Answer 23

Impotence, exacerbation of COPD and asthma, cardiovascular effects (bradycardia, AV block, HF), 
CNS effects (sedation, sleep alterations). May mask the signs of hypoglycemia.

Question 24

Which beta blocker can cause dyslipidemia?

Answer 24

Metoprolol

Question 25

Which beta blocker can exacerbate vasospasm in Prinzmetal's angina?

Answer 25

propanolol

Question 26

Which happens if you give beta blockers alone for pheo or cocaine toxicity?

Answer 26

There will be unopposed alpha agonism, will result in hypertension (soemtimes emergency)

Question 27

How to treat beta blocker overdose?

Answer 27

Saline, atropine, glucagon

Question 28

Which drugs are class III antiarrhythmics?

Answer 28

Amiodarone, Ibutilide, Dofetilide, Sotalol.

Question 29

What is the mechanism of Class III antiarrhythmics?

Answer 29

 Increase AP duration,  ERP,  and QT interval; prolongs phase 3.

Question 30

What are the clinical uses for Class III antiarrhythmics?

Answer 30

Atrial fibrillation, atrial flutter; ventricular | tachycardia (amiodarone, sotalol).

Question 31

What are the toxicities associated with sotalol?

Answer 31

Sotalol—torsades de pointes, excessive β | blockade.

Question 32

What are the toxicities associated with ibutilide?

Answer 32

torsades

Question 33

What are the toxicities associated with amiodarone?

Answer 33

Amiodarone—pulmonary fibrosis, hepatotoxicity, hypothyroidism/ hyperthyroidism (amiodarone is 40% iodine by weight), acts as hapten (corneal deposits, blue/ gray skin deposits resulting in photodermatitis), neurologic effects, constipation, cardiovascular effects (bradycardia, heart block, HF).

Question 34

What are the tests you must order before starting amiodarone?

Answer 34

PFTs, LFTs, TFTs

Question 35

Is amiodarone lipophilic?

Answer 35

yes

Question 36

What are the Class IV antiarrhthymics?

Answer 36

Verapamil, diltiazem

Question 37

What is the mechanism of Class IV antiarrhthymics?

Answer 37

decreases conduction velocity,  prolongs ERP,  prolongs PR interval.

Question 38

What is the clinical use of Class IV antiarrhthymics?

Answer 38

Prevention of nodal arrhythmias (e.g., SVT), rate control in atrial fibrillation.

Question 39

What is the toxicity associated with Class IV antiarrhthymics?

Answer 39

Constipation, flushing, edema, cardiovascular effects (HF, AV block, sinus node depression).

Question 40

How does adenosine work?

Answer 40

 K+ out of cells Žhyperpolarizing the cell and decreasing I Ca. Drug of choice in diagnosing/abolishing supraventricular tachycardia. Very short acting (~ 15 sec).

Question 41

What drugs blunt the effects of adenosine?

Answer 41

Effects blunted by theophylline and | caffeine (both are adenosine receptor antagonists).

Question 42

What are the adverse effects of adenosine?

Answer 42

Adverse effects include flushing, hypotension, | chest pain, sense of impending doom, bronchospasm.

Question 43

When is Mg2+ used as an antiarrhythmic?

Answer 43

With torsades de pointes and digoxin toxicity.