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Anti-Arrhythmic Drugs Flashcards

1
Q

What is normally the primary determinant of the refractory period in cardiac myocytes?

A

AP duration

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2
Q

In pacemaker cells (SA node/AV node), what causes the initial upstroke (depolarization)?

A

Ca2+ influx through T and L-type Ca2+ channels

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3
Q

In pacemaker cells (SA node/AV node), what causes diastolic depolarization?

A

If (funny) current

Inward Na+ current activated at repolarization

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4
Q

What is normally the primary determinant of the refractory period in pacemaker cells?

A

Time

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5
Q

In general, what are the two problems that can lead to arrhythmias?

A

Disturbed impulse formation (EADs, DADs)

Disturbed impulse conduction (blocks, reentry)

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6
Q

When do drugs that inhibit Na+ channels bind best to the receptor?

A

When the M gate is open (during activation of inactivation)

Binds poorly during resting state (M gate closed)

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7
Q

What drug should you give as prophylaxis for the formation of arrhythmias?

A

No drug!
Anti-arrhythmic drugs do not act specifically and can depress conduction in normal cells, leading to drug-induced arrhythmias. You only use anti-arrhythmics when there is an arrhythmia already present.

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8
Q

List the 4 Vaughan Williams classes of anti-arrhythmic drugs

A

Class I: Na+ channel blockers

Class II: Beta-adrenoceptor blockers

Class III: Prolongation of AP duration

Class IV: Ca2+ channel blockers

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9
Q

What is the general mechanism of Class I anti arrhythmics?

A

Na+ channel blockers, slowing the phase 0 upstroke of the AP

Local anesthetic action

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10
Q

What drugs are in the Class IA anti arrhythmics?

A

Procainamide
Quinidine
Disopyramide

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11
Q

What drugs are in the Class IB anti arrhythmics?

A

Lidocaine

Mexiletine

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12
Q

What drugs are in the Class IC anti arrhythmics?

A

Flecainide

Propafenone

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13
Q

What is the effect of Class IA, IB, and IC on the AP duration?

A

Class IA: Prolongs AP duration

Class IB: Shortens AP duration

Class IC: variable

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14
Q

Procainamide

MOA

A

Class IA Na+ channel blocker
Blocks the Na+ channel and slows upstroke of the AP
Lengthens APD

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15
Q

Procainamide

Indications

A

Atrial and Ventricular arrhythmias

Drug of 3rd choice for ventricular arrhythmias after acute MI

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16
Q

Procainamide

Adverse Effects

A

Ganglion blocking properties
Hypotension
Torsades de Pointes induction through its metabolite (NAPA)

Long term - Lupus syndrome (arthritis, pleuritis…)

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17
Q

Quinidine

MOA

A

Class IA Na+ channel blocker

Lengthens APD

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18
Q

Quinidine

Indications

A

Atrial and ventricular arrhythmias

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19
Q

Quinidine

Adverse Effects

A

Hypotension
Anticholinergic effects - increase sinus rate and AV conduction
Ventricular fibrillation
Torsades de Pointes

Long term - Cinchonism: headache, dizziness, tinnitus

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20
Q

Lidocaine

MOA

A

Class IB Na+ channel blocker

Shortens APD

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21
Q

Lidocaine

Indications

A

DOC for ventricular tachycardia or fibrillation

Arrhythmias after MI

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22
Q

Lidocaine

Adverse Effects

A

Least cardiotoxic among Class I

Hypotension
Neurologic effects due to anesthesia

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23
Q

Mexiletine

MOA

A

Class IB Na+ channel blocker

Shortens the APD

24
Q

Mexiletine

Adverse Effects

A

Similar to lidocaine
Hypotension
Neurologic effects

25
Flecainide | MOA
Class IC Na+ channel blocker Also blocks K+ channels No anti-cholinergic effects
26
Flecainide | Indications
Supraventricular arrhythmias in patients with otherwise normal hearts
27
Propafenone | MOA
Class IC Na+ channel blocker that also blocks K+ channels Some weak Beta-blocking activity
28
Propafenone | Indications
Supraventricular arrhythmias in patients with otherwise normal hearts
29
Flecainide | Adverse Effects
Increase mortality in ventricular tachyarrhtyhmias, MI, and ventricular ectopy
30
Propafenone | Adverse Effects
Do NOT use in ventricular tachyarrhythmias Sinus bradycardia (B-blockage) Bronchospasm (B-blockage)
31
What are the class II anti arrhythmics known as?
Beta blockers
32
List some nonselective Beta Blockers
Propranalol Nadolol Timolol Sotalol
33
List some cardioselective Beta Blockers
Metoprolol Atenolol Esmolol
34
Which beta blocker also has some Class III action?
Sotalol
35
Class II Anti Arrhythmics | MOA
``` Inhibit sympathetic influences on cardiac conduction Reduce HR Lower contractility Decrease pacemaker currents Reduce conduction velocity ```
36
Class II Anti Arrhythmics | Indications
``` Prevention of recurrent infarction and sudden death Exercise-induced arrhythmias Atrial fibrillation Atrial flutter AV nodal reentry ```
37
Class II Anti Arrhythmics | Adverse Effects
Bradycardia Bronchospasm May mask tachycardia associated with hypoglycemia in diabetics
38
Class II Anti Arrhythmics | Contraindications
AV block Sinus bradycardia Asthma
39
What is the general mechanism of Class III anti arrhythmics?
Prolong the action potential duration by blocking K+ channels responsible for repolarization
40
Amiodarone | MOA
Class III Prolongs the APD Blocks K+ and Na+ channels May inhibit Beta receptors Weakly blocks Ca2+ channels Suppresses abnormal automaticity
41
Amiodarone | Indications
Oral Recurrent V tachycardia V fibrillation Atrial fibrillation IV 1st DOC for cardiac arrest outside of hospital Termination of ventricular tachycardia or fibrillation
42
Amiodarone | Adverse Effects
- Bradycardia and heart block in patients with AV/SA node disease - Pulmonary toxicity (fibrosis) - Hypothyroid symptoms (block T4 -> T3 conversion) - Photodermatitis - Corneal microdeposits
43
Dronedarone | MOA
Class III | Prolongs the AP duration by blocking K+ channels
44
Why would dronedarone be used instead of amiodarone?
Dronedarone does not have iodine atoms, so it does not block T4 -> T3 conversion
45
What is the general mechanism of action for Class IV anti arrhythmics?
Block Ca2+ channels on vascular smooth muscle, cardiac myocytes, SA/AV nodes
46
What is the only dihydropyridine Class IV drug we discussed? What was its only indication?
Nifedipine Only used for HTN due to high vascular smooth muscle selectivity
47
Verapamil | MOA
Class IV Blocks activated and inactivated Ca2+ channels in the heart Slows AV node conduction Slows SA node automaticity Lowers HR and prolongs PR interval
48
Verapamil | Indications
- Supraventricular arrhythmias - Reentry arrythmias/tachycardias involving the AV node - Slows ventricular rate in atrial flutter/fibrillation
49
Verapamil | Adverse Effects
Vasodilation | Negative inotropic effects
50
Verapamil | Contraindications
Could cause heart block in patients on beta blockers Should NOT be used in patients with a diseased heart and ventricular tachycardia
51
Diltiazem | MOA
Class IV Blocks Ca2+ channels to lower HR and prolong PR interval Increase AV refractoriness and slow SA automaticity
52
Adenosine | MOA
Produces transient cardia arrest Slows AV node conduction and increases AV refractoriness
53
Adenosine | Indications
Used to convert paraoxysal supraventricular tachycardia to sinus rhythm
54
Adenosine | Half life
Short (5-6 seconds)
55
Adenosine | Administration
Always administered as a rapid IV bolus
56
Adenosine | Adverse Effects
``` Flushing SOB Sinus Bradycardia Sinus pauses AV Block ```
57
What are some non-pharmacological anti-arrhythmic therapies?
Vagal maneuvers - Carotid sinus massage - Diving reflex - Valsalva Radiofrequency ablation of the aberrant cells Electrical cardioversion Implantable Cardioverter Defibrillator (ICD)

Pharmacology (67 decks)

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