Anti-arrhythmic drugs

Question 1

What is the major cardiovascular danger of anti-arrhythmic drugs (especially class III agents)?

Answer 1

Anti-arrythmic drugs (especially class III agents) can significantly prolong repolarization (QT) and therefore can result in Torsade de Pointe as a form of Proarrhythmia.

Question 2

What is the only anti-arrythmic that has been shown to improve mortality in the post infarct patient?

Answer 2

Beta blocker

Question 3

What is the preferred therapy for high risk arrhythmia patients (low EF <35% or sustained VT/VF)?

Answer 3

Implantable Cardioverter Defibrillator

Question 4

What are class I anti-arrhythmic drug agents?

Answer 4

Class I => are Na channel blockers

• Class Ia => moderate Na channel blocker (prolongs conduction and repolarization) and increases effective refractory period
• Class Ib => weak Na channel blocker and decreases effective refractory period
• Class Ic => strong Na channel blocker and maintains effective refractory period

Question 5

What are some examples of Class Ia anti-arrhythmic drugs?

Answer 5

Quinidine

Question 6

What are some examples of Class Ib anti-arrhythmic drugs?

Answer 6

Lidocaine

Question 7

What are some examples of Class Ic anti-arrhythmic drugs?

Answer 7

Flecainide

Question 8

What are class II anti-arrhythmic drug agents?

Answer 8

Class II => Beta Blockers

Question 9

How do class III anti-arrhythmic drug agents act?

Answer 9

Class III => K channel blockers that delay depolarization

Question 10

Why is Ibutilide a pseudo class III anti-arrhythmic drug?

Answer 10

Ibutilide causes a slow inward Na current that also delays depolarization

Question 11

What are examples of class III anti-arrhythmic drug agents?

Answer 11

Sotalol, Dofetilide, Amiodarone, Dronedarone

Question 12

How do class IV anti-arrhythmic drug agents act?

Answer 12

Act primarily on slow response cells (SA & AV node), which are dependent on Ca2+ influx for Phase 0 of the action potential.

Question 13

What are 3 examples of class IV anti-arrhythmic drug agents?

Answer 13

Diltiazem

Verapamil

Adenosine

Question 14

How does adenosine work to prevent arrhythmia?

Answer 14

• Blocks A1 receptor
• Prolongs AV conduction by causing cell hyperpolarization and reduces catacholamine stimulation

Question 15

What drugs are used to treat SVT?

Answer 15

Adenosine

Beta blockers

Calcium Channel Blockers

Digoxin

Question 16

What steps are taken if the routine SVT drugs do not work?

Answer 16

• IV: Ibutilide, Quinidine, Procainamide, Amiodarone
• PO: Quinidine, Procainamide, Amiodarone, Disopyramide, Flecainide, Propafenone, Sotalol, Dofetilide, Dronedarone
• DC cardioversion
• Ablation => now generally replaced traditional anti-arrhythmic therapy

Question 17

When does ablation NOT work better than “traditional” anti-arrhythmic therapy?

Answer 17

Atrial fibrillation

Question 18

Which drugs improve survival chances after MI?

Answer 18

Beta blocker (Class II) => propanolol

*Amiodarone (Class III) appears to increase the probability of survival but actually increases cumulative risk => pro-arrhythmia

Question 19

Which drug classes can cause Torsades from Early Afterdepolarization (EAD)?

Answer 19

Class III (K+ blockers)

Class Ia (Na + blockers)

Question 20

How do class Ic anti-arrhythmic drugs cause incessant monomorphic VT?

Answer 20

REMEMBER => Type 1C (Na+ blockers) delay conduction

-Slowing of conduction in limb 1 allows limb 2 to recover by the time the retrograde wavefront arrives at 2; thus facilitating reentry

Question 21

What drugs should be used in acute VT?

Answer 21

IV Lidocaine or Amiodarone till definitive therapy can be instituted

Question 22

Which drugs should be used in sustained VT?

Answer 22

Amiodarone

Sotalol

*However, ICDs are superior

Question 23

What is the most effective treatment strategy for reducing mortality in a patient with a low ejection fraction, and sustained ventricular tachycardia or cardiac arrest?

Answer 23

Empiric ICD