Pharmacology (2)

Question 1

What are the 4 antiarrhythmic drug classes?

Answer 1

Class 1 - Na+ Channel Blockers

Class 2 - Beta (receptor)-Blockers

Class 3 - K+ Channel Blockers

Class 4 - Nondihydropyridine Calcium channel blockers

Question 2

What parts of the cardiac action potential do each drug class inhibit?

Answer 2

Class 1 - Phase 0 (Na+ Channel Block)

Class 2 - Phase 4 (Beta-Blocker; inhibit sympathetic stimulation)

Class 3 - Phases 0-3 (K+ Channel Block)

Class 4- Phase 2 (Ca2+ Channel Block)

Question 3

Which drugs can block the AV node? (4)

Answer 3

Class 2
Class 4
Adenosine
Digoxin

Question 4

Lidocaine and Flecainide are which drug class type? What are their mechanisms of action? Which is strong? Weak?

Answer 4

Class 1

Blocks Na+ channel to slow cardiac AP and HR

Flecainide (1c) – Strong
Lidocaine (1b) – Weak

Question 5

Classify & describe the mechanism of action of amiodarone. What is unique about amiodarone?

Answer 5

Class 3
Blocks K+ channel to increase refractory period of AP –> Lower HR

Has both rhythm and rate control

Question 6

Sotalol and Dofetilide are which drug class type? What are their mechanisms of action?

Answer 6

Class 3

Blocks K+ channel to increase refractory period of cardiac AP –> lower HR

Question 7

Classify and describe the mechanism of action of Dilitazem and Verapamil.

Answer 7

Class 4

Blocks Ca2+ channels to slow conduction speed (& cardiac contractility) –> lower HR.

Question 8

What’s the difference between a dihydropyridine and nondihydropyridine calcium channel blocker?

Answer 8

Dihydropyridine - Will block Ca2+ channels on vascular smooth muscle (for HTN)

Nondihydropyridine - Will block Ca2+ channels on the heart (pacemaker cells & myocytes)

Question 9

What is the effective refractory period (ERP)?

Answer 9

The period of time in which the cell is not excitable.

Question 10

What effect do class 4 drugs have on the ECG waveform? How is this achieved?

Answer 10

By slowing AV node conduction velocity, you will see a prolonged PR interval.

Question 11

What effect do class 4 drugs have on heart muscle contraction? How is this achieved?

Answer 11

They weaken heart muscle contraction. This is because blocking Ca2+ channels shortens phase 2 of the cardiac action potential which means less myocyte contraction.

Question 12

Classify and describe the mechanism of action of Beta-Blockers.

Answer 12

Class 2
Decrease HR by blocking cardiac beta (1>2) receptors that allow Ca2+ influx via GPCR.
This slows down pacemaker conduction (slower upstroke) and decreases myocyte contractility (Phase 2)

Question 13

Classify and describe the mechanism of action of Adenosine.

Answer 13

Miscellaneous
Binds Adenosine Receptor 1 of pacemaker cell to inhibit Ca2+ influx and stimulate K+efflux. –> Slows conduction –> slows HR

Question 14

Classify and describe the mechanism of action of Digoxin.

Answer 14

Miscellaneous

Mimics the vagal nerve to decrease HR (phase 4) and AV node conduction (phase 0).

Also blocks Na/K plus channel leading to more intracellular ca2+ –> increased contractility.

Question 15

Contraindications/Toxicities of Class 1c Drugs?

Answer 15

Contraindicated in patients with coronary artery disease (CAD), history of myocardial infarct (MI), or signs of heart failure (HF)

Question 16

What is a sign of coronary artery disease? Heart Failure?

Answer 16

CAD - positive stress test

HF - low Ejection Fraction (EF) (<55%)

Question 17

Contraindications/Toxicities Class 3 Drugs?

Answer 17

Prolong QT interval –> Torsades de Pointes

Question 18

Contraindications/Toxicities of Amiodarone (Class 3)?

Answer 18

Amiodarone has a lot of iodine which makes it lipophilic. It also has a long half-life.

This can lead to a variety of toxicities in which you must monitor and test for (PulmonaryFT, ThyroidFT, LiverFT)

Increases INR (contraindicated in warfarin patients)

Increases serum drug concentration of statins & Digoxin

Question 19

Contraindications/Toxicities of Class 2 Drugs?

Answer 19

Contraindicated in patients with bradycardia & hypotension.

Question 20

Describe the Van Gogh (“Xanthopsia”) Effect. What drug causes it?

Answer 20

Vision becomes tinted with a “yellow haze.”

Caused by Digoxin.

Question 21

What drugs are capable of rhythm control? What are their classifications? (6)

Answer 21

Flecainide (Class 1c)
Sotalol (Class 3)
Dofetilide (Class 3)
Amiodarone (Class 3)
Lidocaine (Class 1b)
Adenosine (Misc)

Question 22

What drugs are capable of rate control? What are their classifications? (3)

Answer 22

Digoxin (Misc)
Beta-Blockers (Class 2)
Calcium Channel Blockers (Class 4)

Question 23

AVRT & AVNRT are best terminated by what drug (or what maneuver)?

Answer 23

Adenosine (Misc)

Valsalva maneuver can also terminate this (not guaranteed)

Question 24

Scars/Infarcts of the left ventricle are substrates for ____.

Answer 24

Ventricular Tachycardia (Wide complex)

Question 25

What are some common criteria for long-term amiodarone use? (3)

Answer 25

Frequent Episodes of V-Tach
Frequent shocks from ICD
Need maintenance of sinus rhythm to prevent recurrence of a-fib/flutter

Question 26

Which should be used to treat ventricular tachycardia (narrow or wide complex)? (4) What can also be used to treat atrial fibrillation/flutter?

Answer 26

Amiodarone - Also treats a-fib/flutter
Adenosine - AVRT and AVNRT
Lidocaine
Valsava Maneuver

Question 27

What should be used to treat atrial flutter/fibrillation? (5)

Answer 27

Class 1 Drugs (Flecainide only)
Class 2 Drugs
Class 3 Drugs
Class 4 Drugs
Digoxin

Question 28

Nausea and vomiting are most indicative of what type of anti-arrhythmic drug toxicity?

Answer 28

Digoxin toxicity

Question 29

For a sudden (acute) onset of SVT should you use Adenosine or a Class 4 anti-arrhythmic?

Answer 29

Class 4 anti-arrhythmic: In an acute onset of SVT you will want to control the rate. Adenosine should be used in a more chronic state.

If patient is hemodynamically unstable you should electrically cardiovert!