Antiarrhythmics 3

Question 1

Effects of which class of drugs?

1. Prolong the AP duration by reducing the outward (repolarizing) phase 3 potassium current
2. ***Main effect is to prolong the effective refractory period (ERP)
3. Note - phase 4 diastolic potassium current (IK1) is not affected by these drugs.

Answer 1

class 3

Question 2

Which drug’s MOA:

• Blocks I_Kr, I_Na, I_Ca-L channels,
• β adrenoceptors

Answer 2

Amiodarone

Question 3

Effects of which drug?

1. **Prolongs action potential duration and QT interval
2. slows HR and AV node conduction
3. low incidence of torsades de pointes

Answer 3

Amiodarone (class 3)

Question 4

What are the clinical applications of Amiodarone (class 3)

Answer 4

1.** Serious ventricular Arrhythmias

2. **Supraventricular arrhythmias

Question 5

What is the most commonly prescribed AAD?

Answer 5

Amiodarone (Class 3)

Question 6

Pharmacokinetic of which drug?

1. Oral, IV
2. variable absorption and tissue accumulation
3. hepatic metabolism, elimination complex and slow

Answer 6

Amiodarone (class 3)

Question 7

Which drug has the following toxicities?

1. Bradycardia and heart block in diseased heart,
2. peripheral vasodilation
3. **pulmonary fibrosis
4. hepatic toxicity
5. **hyper- or hypothyroidism

Answer 7

Amiodarone (class 3)

Question 8

Which drug has many interactions, based on CYP metabolism

Answer 8

Amiodarone (class 3)

Question 9

The impressive effectiveness of ________ coupled with its low proarrhythmic potential has challenged the notion that selective ion channel blockade by AADs is preferable

Answer 9

Amiodarone

Question 10

What is the MOA of Dofetillide (class 3)?

Answer 10

I_Kr block

Question 11

What are the 2 effects of Dofetillide (class 3)?

Answer 11

1. prolongs action potential
2. Prolongs effective refractory period

Question 12

Clinical application of which med?

Maintenance or restoration of sinus rhythm in A-fib

Answer 12

Dofetillide (group 3)

Question 13

PK of which drug?

Oral

• renal excretion

Answer 13

Dofetillide (class 3)

Question 14

What is the toxicity of Dofetillide (class 3)?

Answer 14

***Torsades de pointes

(initiate in hospital)

Question 15

Interaction of which class 3 med?

Additive with other QT-prolonging drugs

Answer 15

Dofetillide

Question 16

Which class 3 med is used for ventricular arrhythmias and A-fib?

Answer 16

Sotalol

Question 17

Which class 3 med is used for conversion of atrial flutter and A-fib?

Answer 17

Ibutillide

Question 18

Which class 3 drug reduces mortality in patients with A-fib?

Answer 18

Dronedarone

Question 19

Which drug prolongs atrial refractoriness and is effective in A-fib

Answer 19

Vernakalant

Question 20

Effects of which class of drugs?)

•**Reduce inward calcium current during the AP and during phase 4

•**Result= conduction velocity is slowed in the AV node and refractoriness is prolonged

•Pacemaker depolarization is slowed during this phase as well if caused by excessive calcium current.

Answer 20

Class 4

Question 21

Ca2+ channel blockers (L-Type) decrease excitability of SA nodal cells and prolong AV nodal conduction, primarily by slowing the ______ upstroke in nodal tissue.

Answer 21

actional potential

Question 22

Which class of meds are useful in tx of arrhythmias that involve re-entry through the AV node

Answer 22

Class 4

Question 23

High doses of Ca2+ channel blockers can prolong AV nodal conduction to such an extent that______ results

Answer 23

heart block

Question 24

MOA of which 2 drugs?

1. **Dependent I_Ca block slows conduction in AV node and pacemaker activity
2. PR interval prolongation

Answer 24

Verapamil

Diltiazem

Question 25

What is the clinical application of Verapamil?

Answer 25

**\*\*AV nodal arrhythmias, especially in prophylaxis**

Question 26

What is the clinical application of diltiazem (class 4-CCB)?

Answer 26

**\*\*Rate control in A-fib\*\***

Question 27

Which 2 meds have the following toxicities: 1. Cardiac depression **2. \*\*Constipation** **3. \*\*Hypotension**

Answer 27

Verapamil and diltiazem (class 4- CCB)

Question 28

Which group of meds are calcium channel blockers but are not useful in arrhythmias; sometimes precipitate them

Answer 28

Dihydropyridines (group 4- CCBs)

Question 29

MOA of which drug? **\*\*interacts with Na+/K+-ATPase, K+, and Ca2+ channels\*\*** (poorly understood)

Answer 29

Magnesium

Question 30

which drug normalizes or increases plasma Mg?

Answer 30

Magnesium

Question 31

Which drug has the following clinical application: ## Footnote **\*\*Torsades de pointes** **\*\*Digitalis-induced arrhythmias**

Answer 31

Magnesium

Question 32

Pharmacokinetics of which med? ## Footnote IV • duration dependent on dosage

Answer 32

Magnesium

Question 33

What is the toxicity of Magnesium?

Answer 33

Muscle weakness in overdose

Question 34

Which med **increases K+ permeability, K+ currents\*\***

Answer 34

Potassium

Question 35

What are 2 effects of potassium?

Answer 35

1. Slows ectopic pacemakers 2. slows conduction velocity in heart

Question 36

What are the 2 clinical applications of Potassium?

Answer 36

1. Digitalis-induced arrhythmias 2. **\*\*arrhythmias associated with hypokalemia**

Question 37

what 2 toxicities can occur with potassium in the tx of arrhythmias?

Answer 37

**1. \*\*Reentrant arrhythmias** **2. \*\*Fibrillation or arrest in overdose**

Question 38

MOA of which drug? 1. **\*\*Activates inward rectifier I_K** 2. **\*\*blocks I_Ca**

Answer 38

Adenosine

Question 39

What is the effect of Adenosine?

Answer 39

Very brief, usually complete AV blockade

Question 40

What is the clinical application of Adenosine?

Answer 40

**\*\*Paroxysmal supraventricular tachycardias (PSVTs)\*\*** (stops heart with hopes it will reset at normal rhythm)

Question 41

Which med? ## Footnote **\*\*IV only--\> duration 10-15 seconds\*\***

Answer 41

Adenosine

Question 42

What are the 3 toxicities of Adenosine?

Answer 42

**1. \*\*Flushing** **2. \*\*Chest tightness** **3. \*\*Dizziness**

Question 43

In patients with A-fib, therapy is traditionally aimed at what 3 things?

Answer 43

1. Controlling ventricular rate 2. Preventing thromboembolic complications 3. Restoring and maintaining sinus rhythm

Question 44

In patients with A-fib, what 4 meds are used to control ventricular rate?

Answer 44

1. Digoxin 2. Nondihydropyridines 3. CCBs 4. Beta Blockers

Question 45

In patients with A-fib, what 2 meds are used to prevent thromboembolic complications

Answer 45

1. Warfarin 2. Aspirin

Question 46

In patients with A-fib, what 2 meds are used to restore and maintain sinus rhythm?

Answer 46

1. AADs 2. Direct-current cardioversion (DCC)

Question 47

What have studies shown about tx of A-fib?

Answer 47

- no need to try to maintain SR - Rate control alone is often good enough - Chronic AAD therapy may still be needed in pts who continue to have sxs despite good rate control

Question 48

T/F: the use of antiarrhythmic drugs in the US has declined

Answer 48

TRUE because: - some trials show increased mortality w/ AADs - Proarrhythmia is a significant side effect - Advances in technology such as- Ablations and ICDs

Question 49

What technologies are now being used to tx arrhythmias instead of antiarrhythmic drugs?

Answer 49

**ICD** (reduced mortality in EF\<30%) **radiofrequency catheter ablation or cryoablation** (for arrhythmias w/ defined anatomic pathways)